“Mothers’ diets may harm IQs of two babies in three,” warns The Independent. The newspaper reports on its front page that iodine deficiency is widespread among pregnant women.

Iodine is recognised to play a role in the healthy development of the baby’s brain and nervous system while in the womb and the World Health Organization recommends that pregnant women eat iodine-rich foods.

Severe lack of iodine is one of the leading causes of brain damage in the developing world. But a new study, reported in most of the media today, suggests that even mild-to-moderate iodine deficiency during pregnancy may be associated with poorer cognitive function in the child.

In this large study, the iodine levels of pregnant women were measured, and their child’s IQ at age eight and reading ability at age nine were tested.

The researchers found that children of women who didn’t get enough iodine were more likely to be in the lowest quartile for verbal IQ, reading accuracy and reading comprehension. However, there was no significant difference in overall IQ.

A study of this kind has limitations, for example the fact that it relies on measurements being taken at a single point in time. Also, although the researchers adjusted for many factors that may have influenced the relationship (for example, parental lifestyle and socioeconomic factors), the study cannot prove a direct cause and effect relationship between a mother’s iodine consumption during pregnancy and her child’s cognitive ability. It is also not clear whether the differences seen in the children’s verbal and reading skills would translate into ‘real-world’ problems for these children.

Nevertheless, the study does highlight the need for pregnant women to get enough iodine during pregnancy.

Where did the story come from?

The study was carried out by researchers from the University of Surrey and the University of Bristol. No specific funding was reported for the current study, but researchers were supported by the Waterloo Foundation, the Commission of the European Communities, the US National Oceanographic and Atmospheric Administration and Wassen International. The latter is a company that makes and sells iodine supplements. However, none of these organisations had any role in how the study was conducted or how the collected data was interpreted.

This study used information taken from a much larger ongoing cohort study known as the Avon Longitudinal Study of Parents and Children (ALSPAC), which is looking at the health outcomes of children born during the 1990s. The ALSPAC study is supported by the Medical Research Council, the Wellcome Trust and the University of Bristol.

The study was published in the peer-reviewed medical journal The Lancet.

The media reporting is generally representative of the study, although the Mail Online headline writers got into a serious muddle. When they first published the story they used the headline “Drinking organic milk in pregnancy is 'vital for the baby's future brain power'". This was then changed later in the day – "Drinking organic milk in pregnancy could be harming baby’s IQ".

Neither claim is supported by this study. The study did not assess women’s dietary iodine intake from different sources. So it is not possible to say how many women drank organic milk and whether those who did were more likely to be in the iodine deficient group.

What kind of research was this?

The researchers say that the World Health Organization considers iodine deficiency to be “the single most important preventable cause of brain damage” worldwide. Iodine has a role in regulating the thyroid gland, and thyroid hormones have a role in brain and nervous system development. 

The researchers say that changes to dairy farming after the 1930s increased the amount of iodine in milk in the UK. After this and due to the reduction in cases of goitre associated with thyroid problems in the UK it was considered that iodine intake in the UK was sufficient.

However, some more recent UK studies have suggested that mild iodine deficiency may be quite common among adolescent schoolgirls and pregnant women.

The current study used data collected from participants in the Avon Longitudinal Study of Parents and Children (ALSPAC) cohort study to see whether there was an association between pregnancy iodine levels and child cognitive performance. The researchers speculated that women with lower iodine levels during pregnancy would have children with poorer cognitive outcomes.

What did the research involve?

The ALSPAC cohort was eligible to all pregnant women in southwest England with a due date between April 1991 and December 1992.

A total of 14,541 pregnant women were enrolled and 13,988 of their children survived for at least 12 months.

The researchers selected 1,040 women for whom they could measure iodine in the first trimester of pregnancy (up to 12 weeks) and their child’s IQ when they were eight years old.

Iodine was measured in a single urine sample. Urinary iodine levels are said to be a good indicator of iodine levels in the body as 90% of ingested iodine is excreted into the urine. However, the results would have been more accurate if the researchers had been able to measure iodine based on 24-hour urine collection.

To try to reduce the impact of this issue, the researchers looked at the iodine-to-creatinine ratio, which is said to be a good way to get a more accurate iodine measurement. The researchers defined adequate iodine as an iodine-creatinine ratio of 150 micrograms or more per litre. Iodine deficiency was sub-categorised as mild-to-moderate (50 to 150) or severe (less than 50).

Child IQ at the age of eight was assessed using a validated scale (the Wechsler Intelligence Scale for Children). At the age of nine psychologists also assessed children’s reading speed, accuracy and comprehension. 

The researchers looked at the association between pregnancy iodine status and IQ at the age of eight and reading at the age of nine. They adjusted analyses for a wide range of confounders including:

• mother’s age
• mother’s ‘parenting score’ (assessed by looking at cognitive stimulation of the baby, parental education and socioeconomic status)
• home environment, including baby’s emotional and cognitive environment
• family adversity
• stressful events during pregnancy
• infant birth weight and prematureness
• breastfeeding history
• maternal smoking and alcohol intake
• other dietary factors during pregnancy, including intakes of omega-3 fatty acids and iron

What were the basic results?

The researchers found that, overall, the women in the study had an average (median) urinary iodine concentration of 91 micrograms per litre, and average iodine-to-creatinine ratio of 110 micrograms per litre. About two-thirds of women in the study (67%) were iodine deficient in pregnancy. None of the women was using an iodine supplement.

Compared with mothers with adequate pregnancy iodine, those with iodine deficiency were significantly younger and less educated, but had less exposure to stressful life events in pregnancy.

Compared with children of women with adequate pregnancy iodine levels and after adjustment for confounders, children of women with iodine deficiency were at significantly higher risk of:

• having a verbal IQ score in the lowest quartile (odds ratio 1.58, 95% confidence interval (CI) 1.09 to 2.30)
• having a reading accuracy score in the lowest quartile (odds ratio 1.69, 95% CI 1.15 to 2.49)
• having a reading comprehension in the lowest quartile (odds ratio 1.54, 95% CI 1.06 to 2.23)

However, there was no significant association between pregnancy iodine deficiency and performance IQ or overall IQ score – only verbal IQ. There was also no significant association between iodine deficiency and reading score or number of words read per minute – only reading accuracy and comprehension.

How did the researchers interpret the results?

The researchers say that their results demonstrate the importance of having adequate iodine intake during early pregnancy. They say that the results “emphasise the risk that iodine deficiency can pose to the developing infant, even in a country classified as only mildly iodine deficient”. The researchers consider iodine deficiency during pregnancy to be an important public health issue that needs attention.

Conclusion

This is a valuable study that demonstrates that in this subsample of a large cohort of pregnant women in the UK, the majority had inadequate iodine levels during pregnancy.

They also found that this deficiency was associated with poorer verbal IQ in their children at the age of eight, and reading accuracy and comprehension at the age of nine.

The study benefits from its relatively large sample size, from the fact that it followed participants up over time and from the fact that it adjusted for extensive confounding factors.

However, there are some limitations to this study:

• As the researchers say, several 24-hour urine collections would have been the ideal way to measure iodine levels, rather than a single measure, but this would be impractical in a large-scale study.
• It would also be useful to continue to reassess the children’s IQ and reading performance at different time points, particularly as the associations were only found for certain measures of IQ and reading ability. Related to this, it is also unclear what impact these differences in verbal IQ and reading accuracy and comprehension would have had on the children’s learning and school performance. Children’s IQs are not thought to be fixed for life but can change over time.
• Studies in other population samples from other countries would be valuable.

The researchers note that a randomised controlled trial assessing the effect of iodine supplementation in pregnant women on child cognitive ability in areas with mild-to-moderate iodine deficiency would be valuable. They say that they hope to run such a trial in the UK, as current evidence from trials in this area is weak. 

Overall, the study highlights the need for pregnant women to obtain sufficient iodine during pregnancy. The World Health Organization recommends that pregnant and breastfeeding women consume 250 micrograms of iodine a day.

Dietary sources of iodine include dairy products and fish. Pregnant or breastfeeding women who are unable or unwilling to eat these types of iodine-rich dietary sources may need supplements.

If you are pregnant or breastfeeding and are concerned about your iodine levels, speak to your GP or midwife before taking supplements. Supplements will not be suitable for every woman.

Analysis by Bazian. Edited by NHS Choices. Follow Behind the Headlines on Twitter.

Links To The Headlines

Mothers' diets may harm IQs in two-thirds of babies. The Independent, May 22 2013

Iodine deficiency 'may lower UK children's IQ'. BBC News, May 22 2013

Women who drink organic milk in pregnancy could be harming their baby's IQ. Mail Online, May 22 2013

Enough iodine vital in pregnancy – study. The Guardian, May 22 2013

Links To Science

Bath SC, Steer CD, Golding J, et al. Effect of inadequate iodine status in UK pregnant women on cognitive outcomes in their children: results from the Avon Longitudinal Study of Parents and Children (ALSPAC) . The Lancet. Published online May 22 2013

‘Research has found emotional eaters tend to eat more when happy’, reports the Mail Online website.

The news is based on a small study looking at whether experimentally altering mood has an effect on the amount of calories a person eats.

The researchers examined the effects on what they describe as ‘emotional eaters’ – people who reported using food as a coping mechanism for emotions.

A group of 86 students, who said they were either emotional or non-emotional eaters, were shown TV and movie clips to evoke either a positive, negative or neutral mood. The researchers then assessed how much the students ate when provided with bowls of crisps and chocolate, as well as assessing their change in mood.

Emotional eaters who were shown the positive mood-inducing scenes significantly increased their food intake compared to emotional eaters shown the neutral mood-inducing scenes. However, the negative mood-inducing scenes had no effect on food intake of emotional or non-emotional students.

The common assumption is that emotional eaters eat more when in a negative mood, but this study provides very limited evidence to suggest that this may not always be the case.

However, because this experiment was based in a laboratory and researchers did not measure how hungry people were, even this finding should be viewed with caution. As ever, more and better research is needed if people with eating disorders or weight problems are to be helped effectively.

Where did the story come from?

The study was carried out by researchers from Maastricht University in The Netherlands and was funded by the Netherlands Organisation for Scientific Research. It was published in the peer-reviewed journal, Appetite.

The story was picked up by the Mail Online website and it was covered appropriately, although the limitations of the study could have been described in more detail.

What kind of research was this?

This was a laboratory study looking at the effect of experimentally influencing mood changes in a group of students reported to be emotional or non-emotional eaters, and then looking at the effect on their food and calorie intake.

The researchers say emotional eaters are thought to increase their food intake in response to negative emotions, but little is known about the effect of positive emotions on their food intake. Meanwhile, non-emotional eaters are not believed to change their intake levels in response to emotions, and they might even restrict food intake in response.

The main limitation of this research is that a study of a small, select population sample under experimental conditions can only provide very limited indications about the possible influence emotions may have upon the eating patterns of different people in daily life.

For example, if you thought that researchers could be measuring how much you were eating it could make you, perhaps unconsciously, reluctant to eat as much as you normally would. Alternatively, being in this type of study could make you nervous, leading you to eat more than you normally would.

What did the research involve?

The researchers recruited 86 psychology students in their second year at Maastricht University in the Netherlands who received credit points for their participation. The students were predominantly female (75%) and had an average age of 21.6 years (range 19 to 43).

The students answered a series of questionnaires to assess their mental health and eating behaviours. Emotional eating was assessed using a questionnaire called the Dutch Eating Behaviour Questionnaire (DEBQ). Students were asked, ‘Do you have a desire to eat when you’re feeling lonely?’ and provided answers on a five-point Likert scale that ranged from ‘never’ to ‘very often’.

The researchers then carried out a series of experiments in a laboratory setting that aimed to change the student’s mood. Students were randomly allocated to view clips from television or films that aimed to evoke either a positive, negative or neutral mood:

• 28 students were shown two clips to evoke a positive mood. Firstly, they were shown a scene from the television series Mr Bean (which showed Mr Bean struggling to copy answers from his neighbour during an exam). The second clip was taken from the movie ‘When Harry Met Sally’ which showed the famous scene where Meg Ryan’s character simulates an orgasm in front of other diners in a restaurant.
• 28 students were shown one negative clip from the film ‘The Green Mile’, which showed an innocent man being executed.
• 30 students were shown part of a documentary about fishing to evoke a neutral mood.

The students were told to give in to the emotions the clips evoked, and were presented with bowls containing 191g of chocolate (white, milk and dark, equivalent to 1,000 kcal), 225g of salted crisps (1,229 kcal) and 225g of ketchup crisps (1,217 kcal). The bowls were weighed before and after the experiment to determine the amount of food eaten and calorie intake. 

The students were asked to assess their mood using a visual analogue scale (this is essentially a straight line – where the far left of the line represents poor mood and the far right represents very good mood) at five points during the experiment:

• before the experiment began
• immediately after watching the television or movie scenes
• 5 minutes after the experiment
• 10 minutes after the experiment
• 15 minutes after the experiment

The students were told when entering the laboratory that they were taking part in an experiment on the effect of movie clips on taste perception.

The researchers analysed their results using validated methods and adjusted the results for gender, body mass index (BMI), external eating and dietary restraint as assessed by the DEBQ, and negative mood as assessed by the Positive and Negative Affect Schedule (PANAS).

What were the basic results?

Overall, there was no significant difference between emotional eaters eating more than non-emotional eaters who were shown positive, negative or neutral clips.

When looking specifically at only the emotional eaters:

• those shown the positive mood-inducing scenes significantly increased their intake of food compared to those shown the neutral mood-inducing scenes
• there was no difference in food intake between students shown negative mood-inducing scenes and those shown neutral or positive mood-inducing scenes

How did the researchers interpret the results?

The researchers concluded that self-reported emotional eaters respond in a different way to emotions than non-emotional eaters. They say that emotional eaters ate more in a positive mood compared to a neutral mood, whereas non-emotional eaters ate about the same amount in both conditions.

In discussing the results, the researchers say the findings could be of value for the treatment of obesity.

Conclusion

Overall, this small study provides very limited evidence to suggest emotional eaters eat more when feeling in a positive mood. There are several limitations to this study, some of which are noted by the researchers. These include the facts that:

• the laboratory setting may not be an appropriate setting to test emotional eating with different mood feelings. It is possible that students felt uncomfortable in this setting and limited their food intake as they were being watched
• the students were told they were partaking in an experiment of taste perceptions, so may have been inclined to eat more than they normally would have because of what they were told the study was looking at
• no hunger measurements were taken during the study and how hungry each student was could have greatly affected the results
• there was no group included in the study that did not eat, so it is not possible to say from the findings that the changes in mood were due to food intake
• all of the participants were students, so findings may not be the same as if the same experiments were carried out in different groups who report being emotional eaters

To draw firmer conclusions about the effects of mood on emotional eating, larger studies of different groups are required that carry out experiments in more natural environments. 

Analysis by Bazian. Edited by NHS Choices. Follow Behind the Headlines on Twitter.

Links To The Headlines

Forget comfort eating - could happiness be the reason you're piling on the pounds? Mail Online, May 13 2013

Links To Science

Bongers P, Jansen A, Havvermans R, et al. Happy eating: The underestimated role of overeating in a positive mood. Appetite. Published online April 10 2013

"Hungry shoppers 'buy more calories'," BBC News reports in a story based on a very small short-term study. The somewhat artificial study examined the effects of people skipping meals due to everything from busy lifestyles to intermittent diets such as the 5:2 diet.

These intentional or unintentional fasts may lead to unhealthy food choices being made at the shops. This research looked at whether being deprived of food for just a few hours has an effect on the types of food people opt for.

During a simulated shopping experience, the researchers found that people who were hungry selected more high-calorie foods than people who had just eaten a snack.

Similarly, people who went food shopping during times of the day when the researchers expected them to be hungry (late afternoon) purchased more high-calorie foods than people who shopped when the researchers thought they were less likely to be hungry (early afternoon).

However, no definitive conclusions can be drawn from these findings. The research had many limitations, including the fact that the first study was laboratory-based and laboratory findings may not reflect the real world. 

But it is common sense to grab a bite to eat before heading to the shops, and might be worth a try if you do find that shopping when hungry means you make less healthy food choices.

Where did the story come from?

The study was carried out by researchers from Cornell University in the US and was funded by the university. It was published in the peer-reviewed Journal of the American Medical Association (JAMA) Internal Medicine.

The BBC covered the study well, if slightly uncritically, as the study's limitations were not discussed.

What kind of research was this?

This research included two components (a laboratory study and a field study) designed to determine whether short-term food deprivation changes affect food shopping habits.

The researchers say that food deprivation has been shown to change how much food people buy, and fasting is known to alter how the brain reacts to certain foods. They were interested to know whether shopping while hungry also effects the types of food people purchase.

Laboratory and field studies can provide interesting information about how people may react in given situations, but they are prone to bias and confounding. These potential limitations should be kept in mind when considering the results of the study.

What did the research involve?

In the first part of the study, the researchers recruited 68 paid participants with ages ranging from 18 to 62 years. They were asked to avoid eating for five hours prior to the start of the experiment.

The participants were grouped together in sessions of six to 12 people. In half of these sessions, a plate of crackers was offered at the beginning of the experiment and participants were asked to eat enough of the crackers so that they were not hungry. The participants were not offered any food in the remaining sessions.

The groups then completed an experiment meant to simulate buying groceries online. The online store offered a mix of lower calorie foods (including fruits, vegetables and chicken breasts) and higher calorie foods (including sweets, salty snacks and red meat). The products were displayed without prices. The researchers recorded and compared the food choices of individuals who did not eat prior to the study with those who had been offered a snack.

The second study involved the observation of individuals in a more natural setting. The researchers tracked the food purchases of 82 people.

The first group were tracked during the early afternoon, or "low hunger hours" (between 13:00 and 16:00), when the researchers expected them to have had lunch and therefore not be hungry.

The second group was tracked during the early evening, or "high hunger hours" (16:00 to 19:00), when researchers thought they would have gone several hours without a meal.

The researchers characterised the food purchases as either high-calorie or low-calorie, and compared the number of foods that fell into each category between the two participant groups.

They statistically compared the number of low-calorie items, the number of high-calorie items, and the ratio of low- to high-calorie purchases between the groups.

What were the basic results?

The researchers found that participants in the hungry and not-hungry groups of the laboratory study chose a similar number of total items (approximately 14 in the hungry group versus 12 in the not-hungry group).

The two groups also chose similar numbers of low-calorie foods (approximately eight in both groups), but the hungry group selected significantly more high-calorie items (an average of nearly six, compared with four in the not-hungry group).

During the field study, the researchers found that participants in the evening group purchased fewer low-calorie items (approximately eight items) than the afternoon group (approximate average of 11 items). There was no statistical difference in the number of high-calorie foods purchased (approximately four in both groups).

The ratio of low- to high-calorie items (with a higher ratio indicating better food choices overall) was significantly higher in the early afternoon group (approximately four low-calorie items per each high calorie item) compared with the evening group (approximately 2.5 low-calorie items per each high-calorie choice).

How did the researchers interpret the results?

The researchers concluded that, "even short-term fasts can lead people to make more unhealthy food choices" by picking fewer low-calorie foods.

Conclusion

This study suggests that how hungry you are when you shop for food can have an impact on the food you choose.

This may not be too surprising for anyone who has made a quick trip to the shops while hungry and found themselves at the till with a basket full of crisps and biscuits, but no fruit or vegetables.

While interesting, the study has some limitations that should be noted:

• Both experiments were fairly small, with less than 100 people in each.
• A laboratory-based study such as the first experiment tends to be stronger the more it mimics the real world. A simulated online grocery shopping experience that removes item price as a contributing factor is less likely to mirror real-life decision making.
• The field study makes assumptions about hunger levels based on the time of day. This may not be a reliable manner in which to assess hunger – for instance, individuals shopping during the "low hunger hours" of 13:00 to 16:00 may have skipped lunch, while individuals in the "high hunger hours" may have had a late lunch, a snack, or an early dinner.
• Field studies are prone to confounding due to difficulties measuring and controlling for different factors that may also have an influence. It is not reported how the afternoon and evening shoppers differed, and it is possible that the relationship between the time of day and shopping choices was influenced by different participant characteristics, such as age, employment, education, or socioeconomic status, and not by hunger.

The researchers say that short-term fasting is fairly common and can arise from skipping a meal, either intentionally as part of a religious fast or in an effort to lose weight, or unintentionally due to chaotic work schedules.

However, given that it is pretty easy and low-risk to grab a snack before heading out to the supermarket, this may seem like a sensible thing to do – it may have the benefit of subtly changing the foods you buy and consume throughout the week.

If you are trying to lose weight or eat a healthier diet, it may be a good idea to plan your shopping in advance. Options include using an online grocery site or, for a more low-tech equivalent, a good old-fashioned shopping list.

The NHS Choices 5 A DAY meal planner can also help you plan your weekly shop.

Analysis by Bazian. Edited by NHS Choices. Follow Behind the Headlines on Twitter.

Links To The Headlines

Hungry shoppers 'buy more calories'. BBC News, May 6 2013

Links To Science

Tal A, Wansink B. Fattening Fasting: Hungry Grocery Shoppers Buy More Calories, Not More Food. JAMA Internal Medicine. Published online May 6 2013

The health benefits of a Mediterranean-style diet have hit the headlines, with The Daily Telegraph reporting we should, 'Eat oily fish to prevent memory loss,' while the Mail Online focuses on how oily fish can keep the memory 'sharp'.

These somewhat overenthusiastic headlines are based on a large study that looked at how eating habits similar to those seen in Mediterranean countries could affect your chances of developing cognitive impairment.

Researchers found that older adults from the US who followed a Mediterranean-style diet were 13% less likely to have impaired cognitive abilities. This was still the case even after adjustment for other health and lifestyle factors that could also have an influence. However, this association was not seen in people with diabetes.

The Mediterranean diet has been linked to a lower risk of developing several diseases, including cardiovascular conditions such as heart disease and stroke, and forms of dementia (such as Alzheimer's disease).

Drawing conclusions from research into associations between diet and health is difficult, as it is hard to measure the influence of dietary habits properly.

In the case of this study, the diet measurements may be quite specific to the US, so the findings may not apply to British people's diets in the same way.

Overall, however, this large well-conducted study suggests that sticking to a largely Mediterranean-style diet may have benefits for the cognitive functioning of people who do not have diabetes.

Where did the story come from?

The study was carried out by researchers from the University of Athens, the University of Alabama at Birmingham, and other research institutes in the US and the Czech Republic. It was funded by the US National Institutes of Health and was published in the peer-reviewed medical journal Neurology.

The media headlines regarding the importance of eating oily fish instead of red meat do not fully capture the research results. While oily fish is part of the Mediterranean diet, there are many other components that could also have beneficial effects. This study assessed all the components together rather than focusing on oily fish alone, as the media suggests – in fact, the word 'fish' does not appear once in the Neurology article.

Additionally, the 19% reduction in risk quoted by both The Daily Telegraph and the Daily Mail is incorrectly attributed to "people who adhere to a Mediterranean-style diet". This figure actually only applies to non-diabetic people. The risk reduction for the entire study sample was a more moderate 13% reduction in odds. However, both newspapers covered the main methods of the study well.

What kind of research was this?

This was a prospective cohort study that assessed the relationship between how much people adhered to a Mediterranean diet and their odds of developing cognitive impairment over time.

The Mediterranean diet involves eating lots of fruit, vegetables and olive oil, and eating few saturated fats, meat and dairy products. According to the study's authors, the diet has been associated with longer lifespan and a reduced risk of heart conditions, some cancers and Alzheimer's disease. It is the frequent subject of research into the influence of lifestyle on health and longevity.

As a prospective cohort study, this research can tell us how people's diet is linked to new cases of cognitive impairment over time. It also confirms that diet preceded any change in cognitive function, a key factor in assessing causality.

What did the research involve?

As part of the Reasons for Geographic and Racial Difference in Stroke (REGARDS) study, researchers recruited more than 30,000 individuals over the age of 45 from various regions of the United States. At the beginning of the study (baseline), individuals completed a version of the food frequency questionnaire (FFQ) that assessed their dietary habits. It was adapted specifically around foods commonly eaten in the US. Their cognitive functioning was also assessed using the six-item screener (SIS).

Participants were excluded if:

• they had a history of stroke
• there was missing data from the diet questionnaire
• they completed fewer than two cognitive assessments during the study
• the baseline tests revealed impaired cognitive status

The participants were asked to complete the FFQ several times over the first year to validate the results of the baseline diet assessment. The questionnaire was scored on a 10-point scale (0 to 9), with higher scores indicating higher adherence to a Mediterranean diet.

The SIS cognitive assessment was carried out at baseline and on a yearly basis to detect changes in cognitive status and new cases of cognitive impairment. For the statistical analyses, the researchers defined incident (new) cognitive impairment as a change from intact cognitive functions (an SIS score of 5 to 6) to impaired cognitive status during follow-up assessment (an SIS score of 4 or less).

Using data from the FFQ scores, the researchers separated participants into two categories according to their adherence to a typical Mediterranean diet. Scores of 0 to 4 were taken to indicate low adherence, while scores of 5 to 9 indicated high adherence.

The researchers then calculated the odds of new onset cognitive impairment in the group with high diet adherence, and compared this with the odds of new cognitive impairment in the low adherence group.

They adjusted the analyses to control for factors shown to be associated with new-onset cognitive impairment, including:

• demographic factors, such as age, race and sex
• socioeconomic factors, such as region of residence, household income and education
• health status, such as history of heart disease, diabetes, atrial fibrillation, blood pressure, high cholesterol, use of blood pressure medications, symptoms of depression, and perceived general health
• other risk factors, such as body mass index (BMI), waist circumference, smoking status, alcohol use and physical activity level

They also assessed how having diabetes influenced the relationship between diet and cognitive impairment. For this, they carried out two separate analyses similar to those described above: one for individuals with diabetes, and the other for diabetes-free participants only.

What were the basic results?

Main analysis

Links To The Headlines

Eat oily fish to prevent memory loss, researchers claim. The Daily Telegraph, April 29 2013

Want your memory to stay sharp in old age? Eat less red meat and more oily fish. Daily Mail, April 29 2013

Links To Science

Tsivgoulis G, Judd S, Letter AJ, et al. Adherence to a Mediterranean diet and risk of incident cognitive impairment. Neurology, April 30 2013

'One soft drink a day increases Type 2 diabetes risk by a fifth,' The Independent warns, reporting on a European study that has examined the relationship between type 2 diabetes and sugary drinks.

The study – one of the largest of its kind – found strong links between sugary drink consumption and an increase in a person's risk of developing type 2 diabetes. It attempted to assess the potential effects of various soft drinks on diabetes risk, including:

• sugar-sweetened drinks, such as cola
• artificially sweetened drinks, such as diet cola
• fruit juices and nectars (diluted fruit juices that may contain sugar or sweeteners)

The researchers found that people who drank sugar-sweetened drinks were at a higher risk of developing type 2 diabetes. For every additional regular can-sized, sugar-sweetened drink per day, there was an 18% risk of developing the disease. However, drinking artificially sweetened drinks, juices and nectars was not associated with any increased risk.

While this type of research cannot prove a definite cause and effect between sugary drink consumption and diabetes, it does suggest a strong association. As most popular soft drinks now come in a sugar-free alternative, they would certainly seem to be the healthier choice. But a glass of tap water is both healthier and a lot cheaper.

Where did the story come from?

The study was carried out by researchers from Imperial College London and colleagues from eight European countries, and was funded by the European Union.

It was published in the peer-reviewed Diabetologia, the journal of the European Association for the Study of Diabetes, and is freely available to download on an open access basis.

The study was generally covered well by the papers that reported on it. However, many papers reported the increased risk of developing diabetes from drinking sugary drinks as being 22%, which to be fair was included in the press release about the study. The actual risk increase after adjusting for factors such as BMI was 18%.

The Daily Mail also included comments from a spokeswoman for the British Soft Drinks Federation, who sensibly advised that, like most things, soft drinks should be consumed in moderation.

What kind of research was this?

This was a case-cohort study in which researchers used data from a large study looking at how lifestyle and genetic factors interact to increase the risk of developing diabetes. Participants in the study were drawn from the UK, Germany, Denmark, Italy, Spain, Sweden, France and the Netherlands.

The study aimed to evaluate the association between the consumption of sweet drinks (juices and nectars, sugar-sweetened soft drinks and artificially sweetened soft drinks) and type 2 diabetes in European adults.

The authors point out that the consumption of sugar-sweetened drinks has been associated with an increase in the incidence of type 2 diabetes, but previous research has largely been in US populations. This means that the same association may not necessarily apply to Europe.

Consumption of sugar-sweetened drinks, they point out, may lead to type 2 diabetes because of its effect on weight gain. These drinks also have a 'glycaemic effect' that can lead to rapid spikes in blood glucose, as well as disturbances to the hormone insulin, which normally regulates blood sugar.

The association between diabetes and other types of soft drinks, such as fruit juice and artificially sweetened drinks, is less clear.

What did the research involve?

From the larger study (of 330,234 people), researchers selected 12,403 people who developed type 2 diabetes during the approximately 16 years of the study. Anyone who had existing diabetes at the start of the study was excluded from this group.

A diagnosis of type 2 diabetes was ascertained at each study centre in several ways, including through patients self-reporting and linking to GP and hospital registers, hospital admissions and mortality data. For most countries, researchers sought further evidence for the development of diabetes from a minimum of two independent sources, including independent medical record reviews.

The researchers randomly selected a subgroup of 16,154 individuals from the same study (including 778 who developed diabetes during follow-up) to act as a comparison group. The final sample size was 11,684 type 2 diabetes cases and a subgroup of 15,734 (including 730 diabetes cases).

Both groups had completed dietary questionnaires at baseline assessment, including information about their consumption of soft drinks. For most countries, these were divided into:

• sugar-sweetened soft drinks
• artificially sweetened drinks and juices (100% fruit or vegetables, or concentrates)
• nectars (fruit juices with up to 20% added sugar)

Researchers say there was little standardised information from the different European centres on the distinction between fresh and concentrated fruit juices, or between fruit juices and nectars. These categories were therefore studied in combination. They also excluded Italy, Spain and Sweden from their analyses because data from these countries did not distinguish between the different types of soft drinks.

Sweet drinks were divided into the following categories of average consumption:

• less than one glass a month
• between one and four glasses a month
• more than one to six glasses a week
• one glass a day or more

One glass was equivalent to 250g, the standard serving used in the dietary questionnaire.

Participants also completed questionnaires on other factors that could influence results (confounders), including smoking, alcohol, physical activity and educational level. Body weight and height were measured to calculate body mass index (BMI) and participants were categorised into normal weight, overweight and obese.

Most centres also collected information on any history of chronic conditions, such as high blood pressure, high cholesterol, previous cardiovascular disease, and family history of diabetes.

The researchers used standard statistical methods to analyse the association between soft drink consumption and diabetes. They then adjusted their results for confounders such as lifestyle factors and BMI.

What were the basic results?

They found that one 336g (12oz) daily increment in sugar-sweetened and artificially sweetened soft drink consumption was associated with a 22% increase in risk of type 2 diabetes (hazard ratio (HR) 1.22, 95% confidence interval (CI) 1.09 to 1.38) and 1.52 (95% CI 1.26 to 1.83), respectively. An incremental risk applies to someone who had one drink (compared with someone who had none), or someone who had two drinks (compared with someone who had one), and so on.

After adjusting for energy intake and BMI, there was still an association between sugar-sweetened soft drinks and type 2 diabetes (HR 1.18, 95% CI 1.06 to 1.32), but the association with artificially sweetened soft drinks was not statistically significant (HR 1.11, 95% CI 0.95 to 1.31).

The participants' juice and nectar consumption was not associated with type 2 diabetes incidence.

How did the researchers interpret the results?

The researchers say the study corroborates previous research on the association between increased incidence of type 2 diabetes and the high consumption of sugar-sweetened soft drinks in European adults, independent of their BMI.

Conclusion

This is a large, well-designed European study that appears to confirm the health risks of regularly consuming soft drinks. However, this study did have some limitations:

• Dietary assessments were carried out only once, at the start of the study, so it did not take account of any changes in people's consumption of soft drinks over the years.
• Consumption of soft drinks was self-reported, which introduces the possibility of error.
• The definition of juices and nectars included drinks both with and without added sugar. As the authors point out, the lack of any association between this category and diabetes should be interpreted with caution.
• The study cannot establish whether the consumption of sugary drinks causes diabetes. Its results may have been affected by various other factors (called confounders), although researchers tried to take account of these.

It's important to stay well hydrated, especially in warmer weather, but water is the healthiest choice for quenching your thirst. Or, if you can't do without soft drinks, there is almost always a sugar-free alternative.

Analysis by Bazian. Edited by NHS Choices. Follow Behind the Headlines on Twitter.

Links To The Headlines

One soft drink a day increases Type 2 diabetes risk by a fifth. The Independent, April 25 2013

One fizzy drink a day may raise diabetes risk by fifth. The Daily Telegraph, April 25 2013

Diabetes danger in just ONE sugary drink a day: Chance of developing Type 2 increases by a fifth. Daily Mail, April 24 2013

One fizzy drink a day 'raises the risk of diabetes by a fifth'. Metro, April 25 2013

Links To Science

The InterAct consortium. Consumption of sweet beverages and type 2 diabetes incidence in European adults: results from EPIC-InterAct (note – document is in WinZip format). Diabetologia. Published online April 2013

"TV chefs 'adding to obesity crisis by encouraging us to eat fatty dishes'," reports the Metro, with similar stories blaming celebrity chefs for our bulging waistlines in much of the media.

The news is based on analysis of the nutritional values of randomly selected recipes created by celebrity chefs. Researchers found that most of the recipes analysed exceeded national healthy eating benchmarks on fat, saturated fat, sugar and salt intake.

The problem with this study, and the media’s reporting of it, is that it assumes that unhealthy recipes lead to higher rates of obesity, which has not been shown to be the case.

We cannot draw reliable conclusions on the effects of these findings because, for example, we don’t know if these recipes are cooked and eaten frequently and we don’t know how other recipes compare.

It seems unlikely that cooking some of these recipes for a special occasion or as a treat will harm your health, especially if you eat a balanced diet and compensate for treats with healthier options at other mealtimes.

Read more about healthy eating.

Where did the story come from?

The study was carried out by researchers from the Department of Health Professions at Coventry University, and was supported by the department and Faculty of Health and Life Sciences, Coventry University.

The study was published in the peer-reviewed journal Food and Public Health and is freely available on an open-access basis.

This story was widely covered, with nearly all papers leading with a headline blaming TV chefs for making us fatter or adding to the obesity crisis. The researchers’ claims that “Celebrity chefs are a likely hidden contributing factor to Britain’s obesity epidemic” were accepted without any serious scrutiny. The study presents no credible evidence that cookbooks containing unhealthy recipes are directly responsible for obesity rates.

Celebrity chefs can have a positive effect on people’s diets, and to blame them for Britain’s rising obesity levels is an oversimplification of the problem.

Somewhat unfairly, many of the news stories featured a photo of Nigella Lawson. While some of her recipes may be unhealthy, the celebrity chefs included in this study were not named.

A similar study, published in 2012, comparing ready meals with celebrities’ recipes was reported in the same uncritical way.

What kind of research was this?

This was a cross-sectional study that analysed the nutritional composition of British-based celebrity chefs’ recipes.

The researchers wanted to compare the nutrient content with national benchmark recommendations for certain nutrients and healthy eating guidelines, such as the advice to eat less than six grams of salt a day.

Although this study allows conclusions about the nutritional content of recipes to be drawn, it does not assess the impact of celebrity chefs’ recipes on people’s diets. The findings of this study do not allow us to determine whether celebrity chefs are “adding to the obesity crisis”, because, for example, we don’t know how often these meals are eaten.

What did the research involve?

Recipes by celebrity chefs were randomly selected. Celebrity chefs were professional cooks whose recipe books appeared on Amazon’s “top one hundred bestselling books of 2009” or who were featured on the Good Food Channel’s website as a celebrity chef.

To be eligible, recipes had to be suitable for the general public, rather than being targeted at, for example, children or people who wanted to lose weight.

In total, 904 recipes from 26 celebrity chefs were selected at random. All types of recipes (for example breakfast, lunch, starter, evening meal and dessert) were eligible for inclusion.

Researchers used computerised dietary analysis software to work out nutritional content of the recipes. For each recipe they worked out the levels of:

• total energy
• protein
• carbohydrate
• fat
• sodium
• salt

The nutritional value of each recipe was compared against national healthy eating benchmark guidelines using a ‘healthy eating index’, which measured how far each recipe deviated from national recommendations.

What were the basic results?

Recipes from the 26 chefs differed significantly in the energy, protein, carbohydrate, fat and salt and sodium content per portion.

Per portion:

• Recipes from 22 of the 26 chefs had fat content on average above the ‘high fat content’ criteria.
• Recipes from 24 of the 26 chefs had saturated fat content on average above the ‘high saturated fat content’ criteria.
• Recipes from 16 of the 26 chefs had sugar content on average above the ‘high sugar content’ criteria.
• Recipes from seven of the 26 chefs had salt content on average above the ‘high salt content’ criteria.

On average, recipes had nutritional levels substantially above healthy eating guidelines (meaning that on average they contained more fat, saturated fat, sugar and salt than recommended).

The researchers calculated that 13% of recipes met or were below healthy eating guidelines (meaning that on average they had less fat, saturated fat, sugar and salt than the recommended limits), whereas 87% exceeded healthy eating guidelines.

Perhaps unsurprisingly, when the meals were analysed by meal type subgroup, desserts were the meal type that exceeded healthy eating guidelines the most.

How did the researchers interpret the results?

The researchers conclude that, “although variation in the nutritional composition of recipes existed between celebrity chefs, there was still a general trend whereby excessive amounts of total fat, [saturated fat], sugars and salt were evident. The majority of recipes analysed had unhealthy nutritional compositions in accordance with national healthy eating benchmark recommendations, and therefore celebrity chefs could potentially be a hidden contributory factor to current public health nutrition issues, through exacerbating Britain’s already unbalanced dietary intake”.

Conclusion

This study has found that many celebrity chefs’ recipes exceed national recommendations for fat, saturated fat, sugar or salt intake.

However, although the researchers and the media have speculated on the effect that this may have, this research does not investigate this question and no conclusions can be drawn. For example, we don’t know if these recipes are cooked and eaten frequently, and we don’t know how the nutritional value of these celebrity chefs’ recipes compares with more humble cooks’ recipes.

It is also important to repeat the fact that celebrity chefs who targeted their recipes at people concerned about weight management or who were on a diet were excluded from the study.

Often, TV chefs’ recipes are designed to be ‘event meals’, with the meal being cooked for a special occasion such as a birthday or dinner party. It is unlikely that someone would use a cookbook to cook all their meals.

It is similarly unlikely that cooking some of these recipes for a special occasion or a treat will harm your health, especially if you eat a healthy balanced diet the rest of the time.

Read more about healthy eating and good food.

Analysis by Bazian. Edited by NHS Choices. Follow Behind the Headlines on Twitter.

Links To The Headlines

TV chefs ‘adding to obesity crisis by encouraging us to eat fatty dishes’. Metro, April 24 2013

Television chefs adding to obesity crisis with fatty dishes warn academics. The Independent, April 24 2013

Celebrity chefs 'exacerbate Britain's obesity crisis by encouraging people to eat dishes packed with fat'. Daily Mail, April 24 2013

TV chefs get roasting for 'making us fatter'. Daily Express, April 24 2013

Links To Science

Jones M, Freeth EC, Hennessy-Priest K, Costa RJS. A Systematic Cross-Sectional Analysis of British Based Celebrity Chefs’ Recipes: Is There Cause for Public Health Concern? Food and Public Health. Published online 2013

"Beetroot 'can lower blood pressure'," BBC News confidently reports. But the truth about whether beetroot can really lower your blood pressure is a little more unclear than the headlines suggest. The news comes from a study looking at the effect of nitrates on blood pressure in rats and a very small trial in people with high blood pressure.

Nitrates are molecules that occur in some foods, particularly in beetroot. Previous studies have suggested that nitrates can widen the blood vessels, which can lead to a drop in blood pressure. This study found that people who drank about one glass of beetroot juice (or rats given a dose of nitrate) had a short-term reduction in blood pressure.

The researchers argue that the use of beetroot juice, or other nitrate-rich foods, could be a useful extra treatment option for people with high blood pressure.

Despite the interesting findings, the study has some significant limitations:

• only 15 people were involved
• it did not look at whether regular consumption of beetroot juice reduced the long-term complications of high blood pressure, such as heart disease

Larger studies assessing the long-term effects of beetroot juice on high blood pressure and its complications are needed before it can be recommended as a way of lowering blood pressure.

Where did the story come from?

The study was carried out by researchers from the William Harvey Research Institute at Barts and The London School of Medicine and Dentistry, Queen Mary University of London, the University of Exeter Medical School, and Kings College London, all in the UK.

It was funded by the British Heart Foundation and was published in the peer-reviewed medical journal Hypertension.

Two of the study's authors disclose a potential conflict of interest as directors of HeartBeet Limited, which appears to be a company that sells beetroot juice and is listed at the same address as the firm that supplied the beetroot juice used in the study.

The headlines in the UK media proclaiming that beetroot "can lower blood pressure" are premature. It would be more accurate, if less sexy, to qualify this by adding "in the very short term". This research did not look at the effect of nitrate on blood pressure for longer than a 24-hour period and we don't know enough about its lasting effects.

What kind of research was this?

The researchers carried out two types of investigations. They first investigated the effect of ingested nitrate on blood pressure among rats. The researchers then carried out a randomised crossover trial on just 15 people. This second investigation aimed to see if dietary nitrate – in the form of beetroot juice – had an effect on blood pressure among people with known high blood pressure.

A randomised crossover trial is a type of study where people receive all of the treatments and are tested in a random order. This is an appropriate study design for looking at this type of research question. It means that people receive one treatment, the effect is measured, and they then 'cross over' into the other treatment group, where the effect of the second treatment (or control) is also measured.

What did the research involve?

For the first part of their study, the researchers investigated the effects of giving different doses of nitrate to healthy rats and rats that had artificially raised blood pressure. The researchers looked at the effect this had on the rats' blood pressure.

For the second part of their investigations, the researchers recruited eight women and seven men who were identified as having high blood pressure (hypertension) at a screening procedure a month before the study began. These participants were not taking any blood pressure medication.

The average age of participants was 52.9 years and they were all considered to have grade 1 hypertension, with readings of:

• systolic blood pressure (the pressure of the blood when the heart beats to pump blood out) between 140 and 159mmHg
• diastolic blood pressure (the pressure of the blood when the heart rests between beats) between 90 and 99mmHg

The agreed definition of high blood pressure is a systolic pressure reading of 140mmHg and a diastolic pressure reading of 90mmHg (140/90mmHg).

Participants were randomly assigned to drink either 250ml of beetroot juice (supplied by a firm at the same address as the company that two of the authors are directors of), considered the experimental group, or 250ml of water (containing a small amount of nitrate), which acted as the control group. In order to elevate levels of nitrite, the participants having the beetroot juice were said to have received a dose of 3.5mmol nitrate that caused a 1.5-fold increase of plasma [nitrate].
 
The participants then had their blood pressure monitored over a 24-hour period: every 15 minutes for the first three hours, then hourly for a further three hours, and again at the 24 hour mark. Participants also had their blood pressure recorded prior to the study to provide a pre-intervention blood pressure reading. After seven days, participants 'crossed over' to receive the alternative drink.

The researchers said that beetroot juice was well tolerated by the people who were given it in terms of side effects.

What were the basic results?

The main results of this study were:

Animal findings

• nitrate was found to significantly lower blood pressure among rats that had high blood pressure compared with the healthy rats
• the results was found to be dose-dependent – the higher the nitrate dose given to the rat, the bigger effect on reducing blood pressure

Human findings

• consumption of the relatively low dose of dietary nitrate caused a significant decrease in blood pressure (systolic and diastolic) compared with participants who drank water (p<0.001)
• the peak average reduction in blood pressure was 11.2 (±2.6) mmHg in the group that received nitrate compared with 0.7 (±1.9) mmHg in the water group
• after 24 hours, systolic blood pressure remained significantly lower in the group that received nitrate compared with the group that received water, and remained significantly different from values taken at baseline
• diastolic blood pressure remained lower in the group given nitrate up to measurements taken at six hours compared with those given water, but returned to values taken at baseline at the 24-hour mark
• no significant difference in heart rate was seen between the groups of human participants

Links To The Headlines

Beetroot 'can lower blood pressure'. BBC News, April 16 2013

Beetroot juice 'helps lower blood pressure': A glass a day can reduce it by 7%, say researchers. Daily Mail, April 16 2013

One vegetable a day can 'cut blood pressure'. Daily Express, April 16 2013

Links To Science

Ghosh SM, Kapil V, Fuentes-Calvo I, et al. Enhanced Vasodilator Activity of Nitrite in Hypertension - Critical Role for Erythrocytic Xanthine Oxidoreductase and Translational Potential. Hypertension. Published online April 15 2013

"The Cuban diet – eat less, exercise more – and preventable deaths are halved," is the advice in The Independent.

This is not a new Latin diet and dance fad, but news based on research into how Cuba’s rollercoaster economic history has affected the health of the Cuban people.

During the early 1990s, Cuba suffered an economic downturn due to a tight US embargo on imports and the collapse of the Soviet Union, which had been supporting the country.

This led to a drop in the number of calories consumed in the average Cuban diet. Due to the embargo, petrol became virtually unobtainable, and more than 1 million bicycles were distributed by the government, leading to an increase in physical activity.

These factors contributed to an average weight reduction per citizen of 5.5kg over the course of the five-year economic crisis. During this time there was a significant drop in prevalence of, and deaths due to, cardiovascular diseases, type 2 diabetes and cancers.

But once the crisis was over and people started to eat more and exercise less, these trends began to reverse.

The study suggests that population-wide health initiatives that encourage people to eat less and exercise more could achieve significant positive health outcomes. The question is – how, in an affluent Western democracy, do you encourage people to eat less and exercise more if they are not forced to do so?

Where did the story come from?

The study was carried out by researchers from academic centres in Spain, Cuba and the US. There is no information about external funding.

The study was published in the peer-reviewed British Medical Journal.

It was reported accurately in the papers, although headlines like the Daily Mail’s “Lose weight the CUBAN way” and The Independent’s “The Cuban diet” trivialise the hardship that Cuban people underwent during the time in question. While they did enjoy a drop in cardiovascular disease and diabetes deaths during this period, they also experienced a sharp rise in malnutrition-associated disorders, such as neuropathies (nerve damage).

What kind of research was this?

The paper used data from regular cross-sectional health surveys of the Cuban population and drew on cardiovascular studies, chronic disease registries and vital statistics over three decades, from 1980 to 2010.

Its aim was to evaluate the associations between weight change across the whole Cuban population and the incidence, prevalence and death rates from diabetes and death rates from cardiovascular disease and cancer.

The authors say that the health effects of population-wide changes in body weight on a well-nourished population are unknown.

In Cuba, they point out, marked and rapid reductions in mortality from diabetes and coronary heart disease were observed after the economic crisis of the early 1990s when, in the aftermath of the dissolution of the USSR and during the US embargo on imports, there were severe shortages of both food and fuel.

These led to people eating less, and walking and cycling more (the government distributed more than 1 million bicycles during the crisis).

Since this time, the Cuban economy has shown a modest but constant recovery, especially since 2000.

What did the research involve?

The researchers used a variety of sources including national and regional surveys, to track changes in body weight, physical activity, smoking and daily energy intake between 1980 and 2010.

In particular, the authors drew on four cross-sectional surveys of adults aged 15 to 74, in the city of Cienfuegos, a relatively large city on the south of the island.

The surveys, of between 1,300 and 1,600 adults each, took place in 1991, 1995, 2001 and 2010 and included measurements of height and weight, which were used to assess body mass index.

The researchers also drew on national surveys of 14,304 people in 1995, 22,851 people in 2001, and 8,031 people in 2010, which assessed risk factors for chronic disease. They obtained data on diabetes rates from Cuban health registries spanning the period 1980–2009. They obtained information on mortality from diabetes, coronary heart disease, stroke, cancer and all causes for the period 1980–2010 from the Cuban Ministry of Public Health.

They analysed trends of change in disease prevalence and mortality over time and examined how this was related to changes in body weight.

What were the basic results?

Overall, between 1991 and 1995, the era of the economic crisis, the Cuban population experienced an average 5.5kg reduction in body weight. This was accompanied by rapid declines in death rates from diabetes and heart disease.

Between 1996 and 2002 (that is, with a lag of about five years after the crisis) there was an associated reduction in diabetes and cardiovascular disease mortality:

• diabetes death rates fell by 50% (13.95% annually)
• coronary heart disease (CHD) death rates fell by 34.4% (6.5% annually)
• deaths from all causes fell by 10.5%

After the crisis had passed, there was an average population-wide increase in weight of 9kg per person. In 1995, 33.5% of the population were overweight or obese and this increased to 52.9% by 2010.

This weight regain was followed by an increase in diabetes incidence and mortality:

• From 2006 to 2009, there was a 140% increase in diabetes incidence (new cases) and a 116% increase in diabetes prevalence (total number in the population with the condition).
• From 2002 onwards diabetes mortality increased by 49% (from 9.3 deaths per 10,000 people in 2002 to 13.9 deaths per 10,000 people in 2010).
• A slowing in the rate of decline in mortality from coronary heart disease was also observed.

How did the researchers interpret the results?

The researchers say that an average population-wide weight loss of 5.5kg per person was accompanied by diabetes mortality falling by half and mortality from coronary heart disease falling by a third. Increased body weight following the crisis was associated with an increase in diabetes incidence and mortality and a slowing down in the decline in mortality from CHD.

The authors suggest that a modest reduction in calorie consumption would “reverse the global obesity epidemic” and reduce deaths from diabetes by half and CHD by a third.

Conclusion

This is an interesting study that appears to show that modest weight loss within a relatively short period across the whole population is associated with a downward trend in diabetes and reductions in death rates from both diabetes and heart disease.

Similarly, weight regain was associated with an increase in diabetes incidence, prevalence and mortality as well as a slowing down in the decline of cardiovascular deaths.

This type of study draws on many different data sources and, as such, there is a possibility of error. Also, as the authors point out, data was missing on diabetes incidence during the crisis years and diabetes incidence showed wide fluctuations in subsequent years.

It is also difficult to conclude that changes in weight are solely responsible for changes in disease rates as other factors may also have a role. For example, smoking slowly decreased in Cuba during the 1990s.

It is not clear if the findings from the paper can be generalised to other countries. Cuba had, and continues to have, a highly centralised system of government where individual autonomy is limited.

To attempt to enforce a nationwide average reduction in body weight in the UK of 5.5kg per person would probably require a degree of social engineering that most people in this country would find intolerable. As the authors point out, an enforced situation of food and fuel shortages is not something anyone would wish to repeat.

While the study reinforces current health messages about the importance of diet and physical activity and a healthy weight, the best way for governments to attempt to reduce global obesity rates remains unclear.

Analysis by Bazian. Edited by NHS Choices. Follow Behind the Headlines on Twitter.

Links To The Headlines

The Cuban diet: eat less, exercise more - and preventable deaths are halved. The Independent, April 10 2013

Hard times behind fall in heart disease and diabetes in 90s Cuba, says study. The Guardian, April 9 2013

Lose weight the Cuban way: Economic crisis triggered an average weight loss of 11lb and slashed the risk of heart disease and diabetes. Mail Online, April 9 2013

Losing just 8lb can be a lifesaver. Daily Express, April 10 2013

Links To Science

Franco M, Bilal U, Orduñez P, et al. Population-wide weight loss and regain in relation to diabetes burden and cardiovascular mortality in Cuba 1980-2010: repeated cross sectional surveys and ecological comparison of secular trends. BMJ. Published online April 9 2013

“A nutrient abundant in red meat… could raise the risk of heart disease,” the Mail Online website warns.

Its story is based on a study of the nutrient L-carnitine, which is found in red meat, dairy products and some dietary supplements.

A diet high in red meat has been thought to increase heart disease risk, although a very recent study has cast doubt on this, suggesting that only processed meat increases heart disease risk. The study looked at one of the supposed factors in any possible heart disease-related risk from red or processed meat.

In a series of experiments, researchers found evidence that naturally occurring gut bacteria broke down L-carnitine into a product called trimethylamine-N-oxide (TMAO). TMAO is known to contribute towards the hardening of the arteries (atherosclerosis) – a major risk factor for heart disease.

Overall, this study provides some evidence of an association between L-carnitine and heart disease, not a direct cause and effect.

Even if L-carnitine does have this effect, sticking to current UK recommendations (no more than 70g of red or processed meat daily) would mean you were consuming only minimal levels of L-carnitine and therefore not at the level of risk seen by this research, which looked at much higher levels of L-carnitine consumption.

Where did the story come from?

The study was carried out by researchers from Cleveland Clinic in Ohio, US and was funded by various grants from the US National Institutes of Health. The study was published in the peer-reviewed journal, Nature Medicine.

The headline somewhat exaggerated the findings and implications of the research, but overall this story was covered appropriately in the media and coverage reported correctly that part of the study was carried out in mice.

The Mail Online deserves praise for providing a comprehensive and detailed, yet easy to understand, summary of what was a complex series of related experiments.

What kind of research was this?

This was a series of experimental studies looking at the effect of a nutrient called L-carnitine (found in red meat and dairy products) on heart disease risk.

The researchers wanted to assess (as previous research had suggested) whether naturally occurring bacteria converted L-carnitine into a waste product called TMAO (trimethylamine-N-oxide).

TMAO is thought to speed up the build-up of plaque in the arteries (known as atherosclerosis), which is a risk factor for heart disease.

Although the researchers carried out part of their investigations in humans, some testing was performed in mice. It is often difficult to interpret the results of animal research, and caution should be exercised when trying to generalise the findings to humans.

What did the research involve?

In this study. the researchers carried out a series of investigative tests on both humans and mice.

For the human tests, researchers gave the nutrient L-carnitine (found in red meat and dairy products) in the form of a supplement to 77 healthy volunteers, including 26 who were vegans or vegetarians. Some of the meat-eating volunteers were given an extra eight-ounce sirloin steak (equivalent to 180mg of L-carnitine).

The participants were then given antibiotics for one week to supress bacteria in the gut from converting L-carnitine into TMAO. They were then given L-carnitine again. Their blood and urine were tested at the start of the experiment and up to three weeks after ingestion of L-carnitine. Some people also had their faeces tested.

As part of their investigations, the researchers separately checked the levels of L-carnitine in the blood of 2,595 people who were having heart check-ups. They did this to see if there was an association between L-carnitine levels and known cardiovascular disease, or risk of a cardiovascular event (such as a heart attack).

Finally, the researchers looked at the build-up of plaque in the mice’s arteries by comparing a group of mice fed L-cartinine for 10 weeks with normally fed mice. Some of these mice were pre-treated with antibiotics.

What were the basic results?

The main results from this study include:

• Meat-eating volunteers produced more TMAO than vegans or vegetarians following ingestion of L-carnitine
• There was a significant association between L-carnitine concentrations and risk of cardiovascular event among people undergoing heart check-ups, but only in those that had high TMAO concentrations. The researchers noted that this result suggests that TMAO rather than L-carnitine is the main driver of this association.
• Faecal analysis showed significant associations of L-carnitine with levels of TMAO in the blood.
• Feeding L-carnitine to mice doubled the risk of the animal developing plaque build-up in the arterial walls, but only when they had their usual gut bacteria. When the animals were treated with gut-clearing antibiotics, L-carnitine in the diet did not lead to arterial wall build-up.

How did the researchers interpret the results?

One of the lead researchers, Dr Stanley Hazen from the Cleveland Clinic in Ohio, is reported as saying “discovery of a link between L-carnitine ingestion, gut microbiota metabolism and cardiovascular disease risk has broad health-related implications. Carnitine metabolism suggests a new way to help explain why a diet rich in red meat promotes atherosclerosis”.

He goes on to say that “a diet high in carnitine actually shifts our gut microbe composition to those that like carnitine, making meat eaters even more susceptible to forming TMAO and its artery-clogging effects. Meanwhile, vegans and vegetarians have a significantly reduced capacity to synthesize TMAO from carnitine, which may explain the cardiovascular health benefits of these diets”.

The study concludes that there is ‘public health relevance, as L-carnitine is a common over-the-counter dietary supplement’. In an accompanying press release, Dr Hazen recommends that people not use L-carnitine supplements unless advised to for medical reasons.

Conclusion

Links To The Headlines

Red meat nutrient used in weight-loss and muscle-building supplements could cause heart disease. Mail Online, April 7 2013

Red meat chemical 'damages heart', say US scientists. BBC News, April 8 2013

Eating a lot of red meat can cause heart disease. Daily Express, April 8 2013

Links To Science

Koeth RA, Wang Z, Levison BS, et al. Intestinal microbiota metabolism of l-carnitine, a nutrient in red meat, promotes atherosclerosis. Nature Medicine. Published online April 7 2013

‘More bananas and fewer crisps can help ward off strokes’, the Daily Mail reports, saying a study has found that people with high potassium intake have a 24% reduced risk of stroke. Researchers are also reported to say that lowering salt intake could increase benefits further.

Advice to switch from eating crisps to eating bananas is sound, but do we really need to boost our potassium intake?

The headlines stem from a well-conducted systematic review of global evidence on the effects of higher potassium concentration on cardiovascular health in healthy adults.

Good quality evidence suggests that boosting potassium intake to the recommended daily levels is associated with a decrease in blood pressure (by a few mmHg) compared to lower intakes. However, this effect was only found for people with high blood pressure.

Other evidence suggested that higher potassium intake could reduce stroke risk by 24%. However, it’s unwise to draw firm conclusions from these studies about how people’s health is affected by increased potassium intake.

A balanced diet featuring lots of fruit, vegetables and protein should give you all the potassium you need, without the need for supplements. In fact, too much potassium can be harmful, particularly for people with kidney disease or those already on certain blood pressure drugs.

Before you start scoffing bananas or popping potassium pills, it may be wise to talk about your blood pressure with your GP.

Where did the story come from?

The focus of this appraisal is on a study into potassium, carried out by researchers from the World Health Organization’s (WHO) Department of Nutrition for Health and Development, Geneva, Switzerland and other institutions in the UK. Funding was provided by various sources, including WHO funds, the Kidney Evaluation Association Japan, and the governments of Japan and the Republic of Korea. The study was published in the peer-reviewed, British Medical Journal.

The news reports are generally representative of this research.

What kind of research was this?

This was a systematic review that aimed to examine the global literature looking at the effects of potassium intake on health.

The researchers claim that historically, humans tended to have a much higher intake of potassium – above 200mmol/day. Now our intake is much less, due to diets high in processed foods and low in fresh fruit and vegetables, they say, with intake in many countries below the WHO-recommended daily intake of 70 to 80mmol/day.

Because previous studies have linked lower potassium intake to increased risk of high blood pressure and stroke, the researchers consider that increasing potassium intake may help to reduce people’s risk of such chronic conditions.

The researchers say that previous reviews have had inconsistent findings. The WHO initiated the current review to systematically gather the results of studies in healthy adults and children without illnesses that could compromise the body’s potassium balance. The WHO did this to inform future guidelines. The researchers wanted to identify randomised controlled trials (RCTs) looking at:

• how increased potassium intake affected blood pressure, death from any cause and cardiovascular disease in apparently healthy adults
• how increased potassium intake affected blood pressure in apparently healthy children
• how increased potassium intake affected blood lipid (fat) concentrations, kidney function and hormones released from the adrenal glands (such as adrenaline) in apparently healthy adults and children
• what level of potassium intake would result in the maximum benefit for reducing blood pressure, and risk of death and cardiovascular diseases
• whether the effects of increased potassium are affected by factors such as people’s health, diet, or by the type of intervention used to help them increase their potassium intake

If insufficient RCTs were identified, the researchers planned to include less robust study designs, including non-randomised trials and observational studies.

What did the research involve?

The researchers used systematic review methods recommended by the Cochrane Collaboration. They searched numerous electronic databases and manually searched reference lists of studies and reviews. They identified randomised and non-randomised trials which had allocated at least one group of participants to increased potassium intake (intervention) and one group to lower potassium intake (control) for at least four weeks. To be included in the analyses, trials had to have measured potassium from urine samples collected every 24-hours (which can be used to estimate potassium intake). The researchers excluded studies involving:

• acutely ill people
• HIV-positive people
• people admitted to hospital
• people whose urinary potassium excretion was impaired due to a medical condition or drug treatment

Researchers were looking for outcomes related to blood pressure, all-cause mortality, all cardiovascular disease, and specifically stroke and coronary heart disease. They also looked at potential adverse effects of changes in concentrations of blood fat (cholesterol and triglycerides), concentrations of catecholamine (hormones such as adrenaline produced by the adrenal glands at the top of the kidneys) and kidney function. In children, the researchers wanted to find out about blood pressure, blood fats or catecholamine concentrations.

The researchers assessed studies for quality and risk of bias. Where possible, they pooled the results in meta-analyses to estimate the effects of higher potassium intake compared to lower.

What were the basic results?

The researchers identified 37 relevant studies, 35 of which were included in the meta-analysis. Of these, 22 were RCTs of adults, 11 were cohort studies of adults, and one was an RCT of children and one a cohort study of children. Due to the limited search results for children, the researchers broadened their inclusion criteria and identified a further RCT, one non-randomised study, and one additional cohort study in children. The two randomised trials in children included a total of 250 boys and girls aged 13-15 years.

Results for adults

The 22 RCTs in adults included 1,606 participants (individual study size 12 to 353 people) and were conducted across countries worldwide. In 20 studies, participants were given potassium supplements (as the intervention), in one study, participants were given potassium supplements and dietary advice or education, and in two studies the intervention was dietary advice or education alone. The cohort studies in adults included 127,038 people.

Links To The Headlines

Halve our salt intake and save millions of lives, says new report. The Independent, 5 April 2013

More bananas and fewer crisps can help ward off strokes, say scientists. Daily Mail, 5 April 2013

Cutting back on salt key to saving lives. Daily Express, 5 April 2013

Increase potassium and cut salt to reduce stroke risk. BBC News, 5 April 2013

Eat more bananas to reduce risk of stroke, say scientists. The Times, 5 April 2013

Links To Science

Anurto NJ, Hanson S, Gutierrez H, et al. Effect of increased potassium intake on cardiovascular risk factors and disease: systematic review and meta-analyses. BMJ. Published online 5 April 2013

He FJ, Li J, MacGregor GA. Effect of longer term modest salt reduction on blood pressure: Cochrane systematic review and meta-analysis of randomised trials. BMJ. Published online 5 April 2013