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Calorie Control Council Warns Study on Diet Soda and Diabetes in Japanese Men has Some Limitations

ATLANTA (June 7, 2013) — Findings presented in a study on diet soft drink consumption and the risk of developing diabetes in Japanese men is critically flawed.  This study does not prove that drinking diet beverages leads to diabetes; moreover, it is a study of only associations – no actual clinical testing was conducted.  The most likely explanation for the findings is that those who drank diet soda were already on the path to getting diabetes due to other risk factors, not that the diet soda caused diabetes.

The Calorie Control Council cites the following as serious limitations of the study:
  • There were gaps in the study. Although the study spanned 7 years, the researchers only asked the participants how many diet beverages they drank over the course of the previous year once at the beginning of the study.  What and how much subjects drank likely changed over the 7 years of the study, although the authors did not account for it.
  • The results are inconsistent with other research on diet soda and low-calorie sweeteners.  A 2011study out of Harvard found that the risk of diabetes was not associated with diet beverages, but instead was explained by health status, weight change before the study, diet, and body mass index (BMI). Other studies have shown this as well.
  • This study had too small a number of diet soda drinkers to draw a statistically meaningful conclusion.  So few participants (20 out of 2,037) drank diet soda on a regular basis that the researchers had to lump them into another group to do the analysis.  There was a wide variation in how many diet beverages the diet soda “drinkers” had per week – anywhere from 1 to 6.  It is highly unlikely that drinking 8 oz. of diet soda a week could significantly affect diabetes risk.
  • The study cannot determine cause and effect. This study was observational, so it was designed only to show an association, not prove cause and effect.  Additionally, it was conducted on a specific population (male factory workers in Japan), so the findings may not be generalizable to other groups.
  • The results of the study are illogical. Even though the authors noted a link between diet soda consumption (1-6 servings per week) and the rate of diabetes, statistically, that association was very weak.  Curiously, there was no link between the consumption of sugar-sweetened soda and diabetes as other studies have found.  The authors noted that the participants who consumed diet soda tended to be heavier and eat more calories.  Individuals seeking to lose weight or manage their blood sugars often switch to diet beverages.  Low-calorie sweetener use might therefore simply be a marker for individuals already on weight-gain or diabetes trajectories, which continued despite their switching to diet beverages.  This is the most plausible explanation of these findings, not that the diet beverages caused the overweight or diabetes.
  • Other factors may have influenced the findings. Although researchers tried to control for many variables, it is entirely possible that other factors not controlled for that may have influenced results.  The authors failed to control for some risk factors associated with Type 2 diabetes such as fat distribution, metabolic syndrome and coronary artery disease.  When the researchers controlled for age, BMI, family history of diabetes, smoking and a few other factors, the association between diet beverages and diabetes decreased. This points to the possibility that the findings could be attributed to factors unrelated to diet beverage use.
 
Low-calorie sweeteners are some of the most thoroughly studied food ingredients in the food supply. The safety of low-calorie sweeteners has been reaffirmed time and again by leading health and regulatory groups worldwide. For more information about low-calorie sweeteners, visit: www.caloriecontrol.org. For more expert opinions discussing this study, click here.
faq2Do you have questions about low-calorie sweeteners? Want to learn more about maintaining a healthy lifestyle? You asked and we listened. Our resident Registered Dietitians answered the most popular questions about low-calorie sweeteners.

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