Intervention study with a high or low antioxidant capacity diet: effects on circulating β-carotene.

Background and objectives: A cross-sectional observation suggests that total antioxidant capacity (TAC) of the diet positively affects plasma concentrations of b-carotene independent of b-carotene intake. This study was carried out to investigate the effect of two dietary strategies, designed to be comparable in fruits, vegetables, fibre, alcohol and b-carotene intake but substantially different in their TAC, on changes in antioxidant intake and antioxidant status, and in particular in circulating b-carotene concentrations. Subjects: A randomized cross-over intervention trial involving 33 healthy participants and consisting of two 14-day dietary periods (high TAC diet, HT; low TAC diet, LT) with a 14-day washout in between was conducted. Results: Energy, macronutrient, dietary fibre, alcohol and b-carotene intake was not significantly different between LT and HT, whereas intake of other carotenoids and dietary TAC was significantly higher in the HT than in the LT (Po0.001). Circulating carotenoids (with the exception of a-carotene, which followed an inverse trend) and a-tocopherol decreased significantly during the LT and increased during the HT period. Among these, b-carotene almost doubled its concentration in plasma after the HT diet. Conclusions: The increase in circulating b-carotene along with the increase in dietary TAC suggests that plasma b-carotene could be a marker of TAC intake rather than of b-carotene intake itself. This may explain, in part, why b-carotene supplementation alone has shown no benefit in chronic disease prevention and adds to a putative beneficial role of high dietary TAC diets, which merits further investigation.