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In earlier EduFacts communiqués we have summarized reports in the literature evaluating the relationships between dietary intake levels/serum levels of dietary carotenoids and risk of age-related macular degeneration (volume 2, numbers 1, 4, 8, 9, 10, 11, and 14) and cataract (volume 2, number 13; volume 3, numbers 3 and 4). A recent evaluation of the Third National Health and Nutrition Examination Survey (NHANES III) data explored the relationship between diabetes mellitus and serum carotenoid levels (1).

The article points out that diabetes is a condition characterized by oxidative stress. This etiology is hypothesized based on demonstrated increased reactive oxygen species and, lipid peroxidation and increased free radical activity. The authors hypothesize that oxidative stress may result in a lowering of antioxidant concentrations in glucose-intolerant patients.

Methods:

Phase I of NHANES III was conducted between 1988 and 1991. This was a cross sectional survey using a sophisticated design enabling generalization of results to the non-institutionalized U.S. civilian population. Of the phase I subjects, 1665 had oral glucose tolerance tests yielding valid glucose tolerance status. Patients were classified as: 1) normal, 2) impaired glucose tolerance, and 3) newly diagnosed diabetes according to World Health Organization criteria. Five carotenoids were assayed at the CDC laboratory: alpha-carotene, beta-carotene, cryptoxanthin, lutein /zeaxanthin and lycopene. Covariate-adjusted geometric means of these carotenoids were computed for the 3 groups. The covariates included socio-demographic variables, physical activity, alcohol consumption, dietary intake (single 24-hour recall), vitamin use, serum cholesterol, HDL, BP, body mass index and activity levels.

Results:

beta-carotene levels and lycopene levels (adjusted geometric means) decreased linearly with glucose tolerance status.

The authors concluded that the NHANES III data suggest that serum carotenoid concentrations are associated with insulin-resistance and glucose tolerance status. The ordinal status from normal to impaired to new diabetes showed a linear trend with respect to the levels of beta-carotene and lycopene.

References

1. Ford ES, Will JC, Bowman BA, and Venkat Narayan KM. Diabetes Mellitus and Serum Carotenoids: Findings from the Third National Health and Nutrition Examination Survey. Am J Epidemiol 1999;149:168-176.

See EduFacts volume 2, number 16 for a summary of another Diabetes-related nutritional study