Associations between concentrations of alpha- and gamma-tocopherol and concentrations of glucose, glycosylated haemoglobin, insulin and C-peptide among US adults.

Our objective was to study the cross-sectional associations between concentrations of alpha- and gamma-tocopherol and concentrations of glucose, glycosylated haemoglobin, insulin and C-peptide among US adults. We used data for 1289 participants without self-reported diabetes who were aged > or =20 years in the National Health and Nutrition Examination Survey 1999-2000. Alpha-tocopherol concentration was inversely associated with glucose concentration (beta per mmol/l=-0.01064, SE 0.00356, P=0.004) after adjusting for age, sex, race or ethnicity, education, smoking status, concentrations of total cholesterol and triacylglycerols, systolic blood pressure, waist circumference, alcohol use, physical activity, time watching television or videos or using a computer, and use of vitamin/mineral/dietary supplements. Among 659 participants who did not report using supplements, this association was no longer significant whereas the concentration of alpha-tocopherol was inversely associated with concentration of C-peptide (beta per mmol/l=-0.01121, SE 0.00497, P=0.024). Gamma-tocopherol concentration was positively associated with concentration of glucose (beta per mmol/l=0.09169, SE 0.02711, P=0.001) and glycosylated haemoglobin (beta per mmol/l=0.04954, SE 0.01284, P<0.001), but not insulin or C-peptide. The relationships between physiologic concentrations of the various forms of vitamin E and measures of glucose intolerance deserve additional investigation.