The total antioxidant capacity of the diet is an independent predictor of plasma beta-carotene.

Objective: To investigate the contribution of the total antioxidant capacity (TAC) of the diet to plasma concentrations of beta-carotene.

Design: Cross-sectional study.

Setting: Department of Public Health and Department of Internal Medicine and Biomedical Sciences, University of Parma.

Subjects: A total of 247 apparently healthy adult men (n=140) and women (n=107).

Methods: A medical history, a physical exam including height, weight, waist circumference and blood pressure measurements, a fasting blood draw, an oral glucose tolerance test and a 3-day food record.

Results: We observe a negative trend across quartiles of plasma beta-carotene for most biological variables clustering in the insulin resistance syndrome, as well as for traditional and new risk factors for type II diabetes and cardiovascular disease (CVD), including C-reactive protein and gamma-glutamyltranspeptidase (P<0.05). Regarding dietary characteristics, energy-adjusted intake of fat, fiber, fruits, vegetables, beta-carotene, vitamin C, vitamin E and dietary TAC significantly increased with increasing plasma beta-carotene (P<0.05), whereas alcohol intake decreased (P=0.013). Adjusted geometric means (95% confidence interval) of plasma beta-carotene significantly increased across quartiles of dietary TAC, even when single dietary antioxidants were considered in the model (QI=0.087 mg/dl (0.073-0.102); QII=0.087 mg/dl (0.075-0.103); QIII=0.114 mg/dl (0.098-0.132) and QIV=0.110 mg/dl (0.093-0.130); P for linear trend=0.026). When the population was divided on the basis of alcohol consumption, this trend was also observed in subjects drinking <20 g alcohol/day (P=0.034), but not in those with higher alcohol intake (P=0.448).

Conclusions: Dietary TAC is an independent predictor of plasma beta-carotene, especially in moderate alcohol drinkers. This may explain, at least in part, the inverse relationship observed between plasma beta-carotene and risk of chronic diseases associated to high levels of oxidative stress (i.e., diabetes and CVD), as well as the failure of beta-carotene supplements alone in reducing such risk.

Sponsorship: Supported by the European Community IST-2001-33204 'Healthy Market', the Italian Ministry of University and Research COFIN 2001 and the National Research Council CU01.00923.CT26 research projects.