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 β-carotene independent of β-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 β-carotene intake but substantially different in their TAC, on changes in antioxidant intake and antioxidant status, and in particular in circulating β-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 β-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 (P <0.001). Circulating carotenoids (with the exception of α-carotene, which followed an inverse trend) and α-tocopherol decreased significantly during the LT and increased during the HT period. Among these, β-carotene almost doubled its concentration in plasma after the HT diet. Conclusions: The increase in circulating β-carotene along with the increase in dietary TAC suggests that plasma β-carotene could be a marker of TAC intake rather than of β-carotene intake itself. This may explain, in part, why β-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.