Development of a national database for dietary glycemic index and load for nutritional epidemiologic studies in the United States.

ABSTRACT

BACKGROUND: The quality of carbohydrate intake, as measured by the glycemic index (GI), has not been evaluated nationally over the past 2 decades in the United States. OBJECTIVES: We aimed to develop a comprehensive and nationally representative dietary GI and glycemic load (GL) database from 1999 to 2018 National Health and Nutrition Examination Survey (NHANES) and to examine GI and GL time trends and subpopulation differences. METHODS: We used an artificial intelligence (AI)-enabled model to match GI values from 2 GI databases to food codes from United States Department of Agriculture, which were manually validated. We examined nationally representative distributions of dietary GI and GL from 1999 to 2018 using the multistage, clustered sampling design of NHANES. RESULTS: Assigned GI values covered 99.9% of total carbohydrate intake. The initial AI accuracy was 75.0%, with 31.3% retained after manual curation guided by substantive domain expertise. A total of 7976 unique food codes were matched to GI values, of which soft drinks and white bread were top contributors to dietary GI and GL. Of the 49,205 NHANES adult participants, the mean dietary GI was 55.7 (95% confidence interval [CI] 55.5, 55.8) and energy-adjusted dietary GL was 133.0 (95% CI 132.3, 133.8). From 1999 to 2018, dietary GI and GL decreased by 4.6% and 13.8%, respectively. Dietary GL was higher among females (134.6; 95% CI 133.8, 135.5) than among males (131.3; 95% CI 130.3, 132.3), those with ≤high school degree (137.7; 95% CI 136.8, 138.7) than among those with ≥college degree (126.5; 95% CI 125.3, 127.7), and those living under the poverty level (140.9; 95% CI 139.6, 142.1) than among those above the poverty level. Differences in race were observed (Black adults, 139.4; 95% CI 138.2, 140.7; White adults, 131.6; 95% CI 130.5, 132.6). CONCLUSIONS: The national GI and GL database facilitates large-scale and high-quality surveillance or cohort studies of diet and health outcomes in the United States.