Is there any direct relation between consumption of corn tortillas and the incidence of type 2 diabetes mellitus in natives of Mexico?
—Cesar Giannotti, MD, Naperville, Ill.

The traditional Mexican diet is rich in foods with a low glycemic index, such as corn tortillas and beans. I was unable to find literature specifically examining the relationship between diabetes incidence and corn tortilla consumption in Mexico. However, a 2003 study by  Jimenez-Cruz et al examined obese diabetics in Mexico who were placed on flexible diets with a low vs. high glycemic index (Diabetes Care. 2003;26:1967-1970). The study was small (14 subjects), randomized, and controlled, and it had a crossover design with two six-week periods. Although there was no difference in the amount of carbohydrates consumed, the low glycemic index group had better BMI (P=.054), hemoglobin A1c (P=.02), and fasting glucose (P=.04) determinations. It should be noted, however, that when the difference in carbohydrate sources was examined and compared between the two groups, the difference in corn tortilla consumption was not statistically significant (P=.96).
—Susan Kashaf, MD, MPH (119-4)