Glycemic index and glycemic load of the diets of Japanese adults: the 2012 National Health and Nutrition Survey, Japan

Objective: The aim of this study was to examine the dietary glycemic index (GI) and glycemic load (GL) of Japanese adults, as well as their nutritional correlates, in the 2012 National Health and Nutrition Survey, Japan.

Method: Dietary data from 15 618 adults aged ≥20 y, collected using a 1-d weighed dietary record, were analyzed. The GI of foods was assigned based on a stepwise published strategy using values from common GI databases.

Results: Mean (SD) dietary GI and GL were 65.9 (4.9) and 190.1 (59.7), respectively, for men and 63.9 (5) and 149.1 (44.1), respectively, for women. Regardless of sex, the top contributor to dietary GL was white rice (GI = 76; >50%), followed by bread (6-8%), noodles (5-6%), and confectioneries (4-7%). White rice was not only positively associated with dietary GI but also contributed most (∼38%) to interindividual variation in dietary GI. For dietary GL, ∼90% of the interindividual variation was explained by carbohydrate-rich foods (mainly white rice; ∼50%), all of which were positive predictors. At the nutrient level, only carbohydrate intake was positively associated with dietary GI and GL, whereas intakes of all other nutrients including saturated fatty acid and sodium showed inverse associations (with some exceptions).

Conclusion: Dietary GI and GL of Japanese adults were primarily determined by the high GI food white rice, and were thus relatively high compared with values observed in Western countries. A low GI and GL diet was associated with both favorable (higher intakes of micronutrients) and unfavorable (higher intakes of saturated fatty acid and sodium) aspects of dietary intake patterns.