Sugar Sweetened Beverages but Not Diet Soda Consumption is Positively Associated with Insulin Resistance

A longitudinal study examining the association between intake of sugar-sweetened beverages (SSB) and diet sodas on insulin resistance and incidence of prediabetes was published in November issue of The Journal of Nutrition. Researchers used a subsample of participants from the Framingham Heart Study’s Offspring cohort (n=1685). Data from 126-item food frequency questionnaires (FFQ) collected from the fifth (1991-1995) to the eighth (2005-2008) examinations was used for the analysis. Intake of sugar-sweetened beverages was estimated by including  the FFQ 4 SSB items including “1) caffeinated colas with sugar, 2) caffeine-free colas with sugar, 3) other carbonated beverages with sugar, and 4) fruit punch, lemonade, or other noncarbonated fruit drinks.” Diet soda intake was estimated through the use of 3 FFQ items to include “1) low-calorie colas; 2) low calorie, caffeine-free colas; and 3) other low-calorie carbonated beverages.”  Researchers considered an intake of 360mL to be equivalent to one serving. To assess overall diet quality, researchers utilized the 2010 Dietary Guidelines Adherence Index (DGAI). Primary outcomes of interest were fasting plasma glucose, insulin resistance as determined by homeostasis model of insulin resistance (HOMA-IR), and the development of both prediabetes and type 2 diabetes (T2D).

For the primary statistical analysis, researchers adjusted for baseline fasting plasma glucose, age, sex, current smoking status, physical activity level, hypertension, BMI, DGAI, and intakes of energy, alcohol, and fruit juice. For the secondary analysis, researchers replaced DGAI with individual foods (coffee, whole grains, vegetables, red meat, fish, and nuts) to “explore the potential effects of specific food groups on the associations of beverages with the outcomes.”

Researchers found that at baseline, SSB consumers were more likely to be young, male, current smokers, engaging in more physical activity, consuming more energy from fruit juice and with an overall less healthy diet. Compared to SSB consumers, diet soda consumers were slightly younger, less likely to smoke, had higher BMI, greater waist circumference, a higher fasting glucose, and greater insulin resistance. There was no noted sex differences for the diet soda group.

Of the 1695 participants, 823 developed prediabetes. After adjustment for the previously mentioned potential confounders, it was discovered that those in the highest quartile for SSB consumption (consuming 6 servings of SSB per week or more) had a ~46% higher risk of incident prediabetes than those in the lowest quartile. Interestingly, adjusting for BMI change over the course of the study did not significantly alter the results. Conversely, after adjusting for BMI, BMI change over the course of the study, and all other potential confounders, there was no significant association between diet soda intake and incident prediabetes. As for HOMA-IR, a method used to quantify insulin resistance and beta-cell function, a higher SSB intake was associated with a higher HOMA-IR after adjusting for confounders.  In contrast, diet soda intake was not associated with changes in HOMA-IR after adjusting for confounders.

Researchers conclude “that the long-term consumption of SSBs predicts increased insulin resistance and a higher risk of developing prediabetes, independent of body weight. In contrast, long-term diet soda intake was not associated with elevated insulin resistance or prediabetes risk.”