Wednesday November 4 2015
Sugary drinks have been heavily criticised
"Just two sweetened drinks a day can dramatically raise heart risk," The Sun reports. A Swedish study found that men who consumed two or more sugary drinks a day had, on average, a 23% increase in the risk of heart failure.
The study included more than 42,000 Swedish men aged 45 to 79 and data on their estimated daily or weekly intake of sweetened drinks from a food frequency questionnaire completed in 1997.
After a follow-up period of nearly 12 years, men who reported consuming two or more glasses (two 200ml portions) of sweetened beverages a day were 23% more likely to experience heart failure compared to individuals who did not consume any sweetened drinks.
However, the study has a number of limitations – for example, there was no adjustment for salt intake, which is known to raise blood pressure and contribute to the development of heart failure.
In addition, the study only included middle-aged and elderly men, so the results cannot be generalised to the overall population and both genders.
That said, most nutritionists would agree that sugary drinks have an adverse impact on public health, and so-called "sports drinks" are often the worst offenders. A standard 500ml bottle of Lucozade contains 4.8 teaspoons (17.5g) of sugar.
When it comes to hydration, tap water is by far the healthiest, and the cheapest, option.
Where did the story come from?
The study was carried out by researchers from the Institute of Environmental Medicine in Stockholm, Sweden. It was funded by the Swedish Research Council Committee for Medicine and the Swedish Research Council Committee for Infrastructure.
The study was published in the peer-reviewed British medical journal Heart. The study has been made available on an open-access basis, so is free to read online.
The study was widely covered by the UK media both accurately and responsibly.
The Daily Telegraph reported a statement from the researchers at the Karolinska Institute in Stockholm, who said the study findings: "suggest that sweetened beverage consumption could contribute to heart failure development. These findings could have implications for heart failure prevention strategies."
They also quoted Francesco Cappuccio, professor of cardiovascular medicine at the University of Warwick, who said: "high-sugar drinks can contribute to heart failure by increasing weight gain and diabetes". He added: "an alternative explanation (not discussed in the paper) is that high salt intake (salt intake is higher in low socio-economic groups) increases thirst, hence increased drinking, including sweetened drinks. The increase in heart failure could therefore be a consequence of higher salt intake, higher blood pressure and higher heart failure risk."
The Sun and the Mail Online carried a quote from the British Soft Drinks Association chief Gavin Partington, who said, unsurprisingly, that the study was "limited" and that "no definitive conclusions can be drawn about cause and effect".
What kind of research was this?
This was an observational study that aimed to investigate whether drinking sweetened beverages was associated with risk of heart failure in a large cohort of Swedish men. The study was carried out over a period of nearly 12 years to capture the long-term associations of this exposure (1998 to 2010).
Researchers say that more than 23 million people are affected by heart diseases worldwide and the prevalence is increasing among elderly and males. The World Health Organization (WHO) says that more than 80% of premature heart disease and stroke cases are preventable. According to their research predictions, deaths from heart diseases in the UK could be halved by small changes in the risk factors (such as cholesterol) that are associated with these conditions.
Observational studies such as this one, which includes a large population with a long follow-up period, can show us if there is any association between an exposure and an outcome. However, we cannot establish causality from such study designs, as more than one factor may be responsible for the observed outcome.
What did the research involve?
This research included 42,400 Swedish men aged 45 to 79. These individuals were residents of Västmanland counties in Sweden.
All the study participants were asked to complete a food frequency questionnaire (FFQ) designed to assess the Swedish diet in 1997. In this questionnaire, individuals were asked to report their average consumption of 96 different foods and beverages over the past year.
To gather information on sweetened drink consumption, study subjects were asked "How many soft drinks or sweetened juice drinks do you drink per day or per week?". They were also separately asked how much coffee, alcohol, fruit, vegetables, processed meat and fish they consume.
The researchers then recorded heart failure incidence from 1998 to 2010 through the Swedish National Patient Register and the Cause of Death Register, which included the details of diagnosis and treatment.
The participants were also asked about the following commonly known confounding factors that may have influenced the outcome measured:
- history of angina or stroke
- physical activity
- body mass index (BMI)
- educational attainment
- family history of heart attack
What were the basic results?
Over a period of nearly 12 years, 4,113 people were diagnosed with heart failure. Among these, 3,604 were first events of heart failure that required hospitalisation, and there were 509 deaths due to heart failure.
After adjusting the results for all of the potential confounding factors measured, individuals who consumed two or more glasses (two 200ml portions) of sweetened beverages per day were 23% more likely to experience heart failure compared to individuals who did not consume any sweetened drinks (hazard ratio (HR) 1.23, 95% confidence interval (CI) 1.12 to 1.35).
The researchers also observed a strong trend between the lower education level of an individual and higher consumption of sweetened beverages.
How did the researchers interpret the results?
Researchers concluded by saying the "study findings suggest that sweetened beverage consumption could contribute to HF [heart failure] development. These findings could have implications for HF prevention strategies. Further prospective studies examining this relationship are therefore necessitated. Moreover, possible biological mechanisms linking sweetened beverage consumption with HF risk need to be studied carefully."
This observational study found an association between the consumption of sweetened drinks and risk of heart failure.
The study has some strengths, such as the large population size and long follow-up period. However, it has several limitations, which are acknowledged by the researchers. These include the following:
- The study included middle-aged and elderly men, so the results cannot be generalised to all age groups and genders.
- The men were all from Sweden, where there is a different typical diet to that of the UK.
- Researchers collected data on the daily and weekly intake of sweetened drinks in the past year just once in 1997. This introduces two limitations. Firstly, since the participants were asked to report their intake in the past year, there may be some recall bias. Secondly, the dietary habits of these individuals might have changed in the 12-year follow-up period.
- Sweetened drinks included artificially sweetened drinks such as low-calorie fizzy drinks, yet fruit juice was not included in the dietary questionnaire. These factors limit any conclusions we can make about which type of drink may be having a negative effect.
- There was no adjustment for salt intake, which is known to raise blood pressure and contribute to the development of heart failure.
- The study design itself, although helping to establish an association, cannot confirm a causal link.
- The researchers have accounted for a number of commonly noted confounding factors.
- However, there may be some other factors that are not considered in the analysis that may have influenced the observed outcome.
It is no secret that a healthy diet including lots of vegetables, whole fruits and food low in salt, along with an active physical lifestyle, help to prevent a number of ailments. Losing weight (if you are overweight), quitting smoking, lowering cholesterol and reducing alcohol intake also have a positive impact on overall health and in reducing the risk of heart failure.
Most nutritionists would recommend that you and your family should drink sugary drinks as an occasional treat and not as a daily dietary staple.