Gynecological Endocrinology recently published a systemic review and meta-analysis examining the relationship that glycemic index (GI) and glycemic load (GL) have with gestational diabetes mellitus (GDM), as well as any dose dependence. This analysis included 13 studies (11 observational and 2 case-control) and nearly 40,000 pregnant women. The glycemic index is a score that ranks the ability of the carbohydrates in specific foods to raise blood glucose levels (in reference to white bread or pure glucose), while the glycemic load also captures the availability of those carbohydrates. There are some foods where these two measures can have significant variation; donuts and watermelon have the same GI, for example, but there are more available carbohydrates in donuts, which have a GL more than twice as high as watermelon.
Although there was a small and notable increase in risk for GDM with diets higher in GI, this association was not found to be significant. However, after adjustment for other variables, a significant positive association was observed between GL and GDM. After adjustment, this dose-responsive association was found to increase the risk for GDM by 0.94% for each unit increase in GL (between 0 and 75). Thus, a diet with a GL of 75 would carry approximately a 50% higher risk for developing GDM compared to a diet with a GL of 25. Given that approximately 7% of women in the U.S. and Canada develop GDM during pregnancy, this meta-analysis may help to provide guidelines for reducing risk, specifically targeting lower GL foods.