Abstract: Background
The quality of carbohydrate intake, as measured by the glycemic index (GI), has not been evaluated nationally over the past two decades in the United States (US).
Objective
We aimed to develop a comprehensive and nationally representative dietary GI and glycemic load (GL) database from 1999-2018 National Health and Nutrition Examination Survey (NHANES) and to examine GI and GL time trends and sub-population differences.
Design
We employed an artificial intelligence (AI)-enabled model to match GI values from two GI databases to food codes from US Department of Agriculture, which were manually validated. We examined nationally representative distributions of dietary GI and GL from 1999-2018 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 7,976 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% CI: 55.5, 55.8] and energy-adjusted dietary GL was 133.0 [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 [133.8, 135.5] than males 131.3 [130.3, 132.3], those with ≤ high school degree 137.7 [136.8, 138.7] compared to those with ≥ college degree 126.5 [125.3, 127.7], and those living under the poverty level 140.9 [139.6, 142.1] compared to above. Differences in race were observed (Black adults 139.4 [138.2, 140.7]; White adults 131.6 [130.5, 132.6]).
Conclusion
We developed a national GI and GL database to facilitate large-scale and high-quality surveillance or cohort studies of diet and health outcomes in the US.