Vitamin C and hyperglycemia in the European Prospective Investigation intoCancer - Norfolk (EPIC-Norfolk) study - A population-based study

OBJECTIVE - To examine the cross-sectional association between plasma vitam in C, self-reported diabetes, and HbA(1c). RESEARCH DESIGN AND METHODS - Data from a population-based study of diet, c ancer, and chronic disease were analyzed. A total of 2,898 men and 3,560 wo men 45-74 years of age who were registered with general practices in Norfol k, U.K., were recruited to the European Prospective Investigation Into Canc er-Norfolk study between 1995 and 1998. RESULTS- Mean plasma vitamin C levels were significantly higher in individu als with HbA(1c) levels <7% than in those with self-reported diabetes or pr evalent undiagnosed hyperglycemia (HbA(1c) greater than or equal to 7%). An inverse gradient of mean plasma vitamin C was found in both sexes across q uintiles of HbA(1c) distribution <7%. The odds ratio (95% CI) of having pre valent undiagnosed hyperglycemia per 20 mu mol/l (or 1 SD) increase in plas ma vitamin C was 0.70 (0.52-0.95) (adjusted for sex, age, BMI, waist-to-hip ratio, tertiary education, any use of dietary supplements, vegetarian diet , alcohol consumption, physical activity, dietary vitamin E, dietary fiber, dietary saturated Fat, and smoking history). The unadjusted change in HbA( 1c) per 20 mu mol/l increase in vitamin C estimated by linear regression wa s - 0.12% (- 0.14 to - 0.09) in men and -0.09% (-0.11 to -0.07) in women. A fter adjusting for the possible confounders, these values were - 0.08% (- 0 .11 to -0.04) in men and -0.05% (-0.07 to -0.03) in women. CONCLUSIONS - An inverse association was found between plasma vitamin C and HbA(1c). Dietary measures to increase plasma vitamin C may be an important public health strategy for reducing the prevalence of diabetes.