Background: Persons with non-insulin-dependent diabetes mellitus (NIDDM) are at increased risk for cardiovascular disease, partly due to concomitant worsening of traditional risk factors including dyslipidemia and hypertension. Based on evidence from small, controlled clinical trials, we hypothesized that increased intake of vitamin C would be associated with improved cardiovascular disease (CVD) risk factor status among community-dwelling persons with NIDDM.
Methods: In separate but parallel statistical analyses, hypotheses were evaluated among persons with NIDDM confirmed by WHO criteria from the Insulin Resistance Atherosclerosis Study (IRAS, n = 520) and from the San Luis Valley Diabetes Study (SLVDS, n = 422). For IRAS, diet and vitamin supplement use was assessed by food frequency interview and for SLVDS, by 24-hr dietary recall interview.
Results: Mean vitamin C intake (mg/day) was 275 for IRAS and 133 for SLVDS, including supplements. In cross-sectional regression models from each data set, vitamin C intake was not associated with systolic or diastolic blood pressure nor with HDL-C, LDL-C, or triglycerides (P values > 0.10; adjusted for calories, demographic and lifestyle variables, obesity, diabetes duration, and medications). In prospective analyses including 285 SLVDS participants, baseline vitamin C intake was not related to any of these CVD risk factors measured an average of 4 years later nor to change in CVD risk factor status during the follow-up period.
Conclusions: We conclude that, across a wide range of intake, vitamin C does not appear to be associated with improved CVD risk factor status among community-dwelling persons with diabetes.