Dietary carbohydrate quality and quantity in relation to the incidence of type 2 diabetes: A prospective cohort study of middle-aged and older Korean adults.

Objectives: This study aimed to investigate whether dietary glycemic load (GL), glycemic index (GI), and carbohydrate intake were prospectively associated with incident type 2 diabetes mellitus (T2DM) in a middle-aged and older Korean populations.
Methods: Data from the Korean Genome and Epidemiology Study were used. A total of 7294 Korean adults ages 40 y to 69 y and with no previous diagnosis of T2DM or cancer at baseline were followed for 10 y. Dietary GL, GI, and carbohydrate intake were estimated on the basis of participants' responses to a validated, semiquantitative, food-frequency questionnaire at baseline. T2DM was defined according to the World Health Organization and International Diabetes Federation criteria.
Results: During 7.7 y (56 377 person-years) of follow-up time, 1259 participants (17.3%) developed T2DM. Grain and its products (particularly refined and whole grains) were the greatest contributors to dietary GL. In the multivariable Cox models, dietary GL was differentially associated with T2DM risk by sex. Men in the highest quintile demonstrated a higher risk of T2DM incidence than did those with the lowest, energy-adjusted, dietary GL (hazard ratio for fifth vs. first quarter = 1.26; 95% confidence interval, 1.05-1.52; P for trend < 0.05) but no association between dietary GL and the risk of T2DM was observed in women. Similar to the findings from the main models, the effect of dietary GL on T2DM incidence according to body mass index, abdominal obesity, and physical activity levels differed substantially by sex.
Conclusions: High GL diets may increase the risk of the development of T2DM in middle-aged and older Korean men but not in women. Nutrition education and emphasis on self-monitoring of dietary carbohydrate quality and quantity of overall diets is necessary in the middle-aged and older Korean populations.
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