Thursday November 14 2013
Acid is produced when the body breaks down certain foods
“Eating too much meat ‘raises risk of diabetes’ even if they eat lots of fruit and vegetables too,” reports the Mail Online.
The headline is based on the results of a 14-year study of more than 60,000 women in France, which looked at whether ‘dietary acid load’ is associated with risk of type 2 diabetes.
Dietary acid load is a term used to describe the amount of acid produced by the body as it breaks down food and drinks.
Meat has a high dietary acid load. Though somewhat counterintuitively, despite the fact that many fruits are acidic, once the body has processed them, they actually reduce dietary acid load.
The study found that higher dietary acid load was associated with increased risk of diabetes.
However, contrary to many of the headlines, higher dietary acid load was associated with increased risk of diabetes even when dietary patterns including meat and fruit and vegetable intake were adjusted for.
This suggests that specific foods and drinks that provide the acid/alkaline components are not important, but what is important is the overall balance; a healthy diet based on the always useful advice of “everything in moderation”.
Where did the story come from?
The study was carried out by researchers from INSERM (Institut national de la santé et de la recherche médicale), Paris-South University and CHU (Centre Hospitalier Universitaire de Rennes), France, and the National Institute of Public Health of Mexico.
It was funded by the Mutuelle Générale de l’Education Nationale, the Institut de Cancérologie Gustave Roussy, the Institut National de la Santé et de la Recherche Médicale and the European Union.
The study was published in the peer-reviewed journal Diabetologia.
The research article is available on an open access basis from the journal’s website as a downloadable zip file (233Kb).
The Mail Online concentrated on the harms of eating too much meat. However, the study didn’t directly look at the effect of meat consumption on the risk of types 2 diabetes.
A diet rich in animal protein is associated with a higher dietary acid load. And fruit and vegetables conversely reduce dietary acid load.
However, dietary acid load was associated with the risk of diabetes in this study even when dietary patterns including meat and fruit and vegetable intake were adjusted for.
This suggests the individual foods and drinks providing the acid/alkaline components are not important, and what is important is the overall balance.
So it’s probably okay to eat some meat as long as you balance it out with your recommended five portions a day of fruit and vegetables.
What kind of research was this?
This was a cohort study that aimed to see whether dietary acid load is associated with risk of diabetes.
A cohort study is the ideal study design to address this question, but it can’t prove that dietary acid load is the causative factor that increases the risk of diabetes.
This is because there are potentially other factors, called confounders, which could be responsible for the association seen.
What did the research involve?
The researchers analysed information from 66,485 female teachers in France without diabetes who had completed a dietary questionnaire. The women were taking part in a larger, European wide cohort study: the European Prospective Investigation into Cancer and Nutrition. As part of this study, the women regularly completed questionnaires about health related information and newly diagnosed diseases, and drug use was monitored using a drug reimbursement claim database.
From the responses to the dietary questionnaire, the researchers calculated two dietary acid load scores: PRAL (Potential renal acid load) and NEAP (Net endogenous acid production). The PRAL score depends on the amount of protein, phosphorus, magnesium and calcium in the diet, and the NEAP score depends on the amounts of protein and potassium eaten.
The women were followed up for 14 years to see whether they developed diabetes.
The researchers analysed whether women with higher dietary acid loads were at increased risk of diabetes.
The researchers tried to adjust their analyses for a number of factors that could confound the relationship, including:
- smoking status
- physical activity,
- blood cholesterol levels (hypercholesterolaemia)
- family history of diabetes
- alcohol intake
- omega 3 fatty acid intake
- carbohydrate intake
- energy from fat and protein
- dietary patterns
- sugar and artificially sweetened beverages
- fruit and vegetables
- processed meat consumption
- adiposity (fatness)
- body mass index (BMI)
What were the basic results?
During the 14 years of follow-up 1,372 women developed diabetes.
There was a trend that increasing dietary acid load was associated with increasing risk of diabetes.
The 25% of women with the highest acid load according to the PRAL score were at 56% increased risk of diabetes compared with the 25% of women with the lowest acid load (Hazard ratio [HR] 1.56, 95% confidence interval [CI] 1.29 to 1.90).
Similar results were seen when the NEAP score was used: the 25% of women with the highest acid load according to the NEAP score were at 57% increased risk of diabetes compared with the 25% of women with the lowest acid load (Hazard ratio [HR] 1.57, 95% confidence interval [CI] 1.30 to 1.89).
When the researchers divided women according to their BMI, they found that high PRAL and NEAP scores were associated with higher type 2 diabetes risk in both normal-weight (<25kg/m2) and overweight/obese women (>25kg/m2), but that the association was stronger in normal-weight women.
How did the researchers interpret the results?
The researchers conclude that “this is the first prospective cohort study to show that a dietary acid load is directly associated with an increased risk of type 2 diabetes”. They go on to state that this finding could have the implication that “dietary recommendations should not only incriminate specific food groups but also include recommendations on the overall quality of the diet, notably the need to maintain an adequate acid/base balance.”
This large cohort study has found that dietary acid load is associated with risk of diabetes in women in France.
Dietary acid load was associated with the risk of diabetes even when dietary patterns including meat and fruit and vegetable intake were adjusted for.
This suggests that the individual foods and drinks providing the acid/alkaline components are not important, and what is important is the overall balance.
This study has the strengths that it was a large cohort study with a long follow-up.
Its weaknesses are that information on diet was only collected at the start of the study, and may have changed over time, and that only women were included in the study.
In addition, cohort studies can’t show causation, and there may be other factors (confounders) not adjusted for that are responsible for the association seen.
Current evidence suggests that the most effective way to reduce your diabetes risk is to try to achieve or maintain a healthy weight – a BMI of between 18.5 and 24.9.
Read more about reducing your diabetes risk.
Analysis by Bazian. Edited by NHS Choices. Follow Behind the Headlines on Twitter.