Tufts Study Absolves Diet Soda in Prediabetes, but Sugary Beverages Are Linked

Studies of the effect of diet soda on diabetes and obesity have produced mixed results.

While sugary beverages have been linked to diabetes and obesity, the evidence has been mixed on diet drinks. A new study from Tufts University finds that regular consumption of sugar-sweetened beverages is associated with a greater incidence of insulin resistance and a higher risk of developing prediabetes among middle-aged adults, while the same was not true with diet soda.1

The findings, published in the Journal of Nutrition earlier this month, involved an analysis of 1685 adults over a 14-year period. Data were culled from the Framingham Heart Study’s Offspring Cohort, a program of the National Heart, Lung, and Blood Institute that tracks multiple generations for lifestyle characteristics that cause cardiovascular disease.

Diet soda has not always fared well in studies examining connections to diabetes and obesity. One 2015 study published in the Journal of the American Geriatrics Society found that greater diet soda intake was linked to higher levels of abdominal fat in adults 65 years or older.2 Other studies suggest that those who drink diet soda believe they can justify consuming higher amounts of high-calorie foods.

In the new study, however, consumption of diet soda was not associated with prediabetes or insulin resistance over an extended period among participants who were 51.9 years on average when the study began; 59.6% of the participants were women. The group had an average body mass index (BMI) of 26.3, which is past the CDC cut-off for overweight.

The researchers found that sugar-sweetened beverage intake was linked to incident prediabetes, with those who consumed the most sugary beverages—more than 3 servings a day, or a median of 6 servings a week—having a 46% higher risk of developing prediabetes than those who did not consumer sugary drinks at all. Sugary drink consumption was also linked to a greater likelihood of insulin resistance.

By contrast, there were no prospective links between drinking diet soda and a risk of prediabetes or changes in insulin resistance, after adjusting for changes in BMI.

One finding that was not in dispute was the connection between sugary beverages and the increase in prediabetes and insulin resistance, according to senior author Nicola McKeown, PhD, an associate professor at the Friedman School of Nutrition Science and Policy at Tufts. “Although our study cannot establish causality, our results suggest that high sugar-sweetened beverage intake increases the chances of developing early warning signs for type 2 diabetes,” she said in a statement. “If lifestyle changes are not made, individuals with prediabetes are on the trajectory to developing diabetes.”

CMS has proposed paying for the National Diabetes Prevention Program to help those diagnosed with prediabetes change their diet and exercise habits to avoid progressing to diabetes. If the program proceeds, Medicare would start reimbursement on January 1, 2018.

References

1. Ma J, Jacques PF, Meigs JB, et al. Sugar-sweetened beverage but not diet soda consumption is positively associated with progression of insulin resistance and prediabetes. J Nutrition. 2016; 146:1-7. doi: 10.3945/jn.116.234047.

2. Fowler SPG, Williams K, Hazuda HP. Diet soda is associated with long-term increases in waist circumference in a biethnic cohort of older adults. J Am Geriatr Soc. 2015;63(4):708-15. doi: 10.1111/jgs.13376.