Effects of 4 y of oral supplementation with β-carotene on serum concentrations of retinol, tocopherol, and five carotenoids

Abstract

β-Carotene has been studied widely as a potential cancer-preventing agent. Recent studies found that subjects who took β-carotene supplements orally had increases in their serum concentrations of α-carotene and lycopene that were large (> 150% increase) and significantly greater than such increases in subjects who received placebo and that similar supplementation was associated with a decrease of ≃37% in plasma lutein concentrations. A biologic interaction between β-carotene and other carotenoids was suggested. We measured concentrations of retinol, α- tocopherol, and five carotenoids in serum specimens from a random sample of subjects enrolled in a clinical trial of the use of antioxidant vitamins in preventing colonic adenomas. We used serum specimens obtained at enrollment and after the subjects took placebo (n = 54) or 25 mg β-carotene/d (n = 54) orally for 4 y. In a multivariate analysis, baseline serum concentrations of the analytes, sex, body mass index, diet, smoking status, and age were associated with variable changes in some analytes over the 4-y period but supplementation with β-carotene was related only to a mean increase in serum β-carotene itself of 151%. We excluded with 95% confidence an increase in lycopene > 4.9%, an increase in α-carotene > 17.6%, and a decrease in lutein > 14.7% in subjects given β-carotene. These results confirm previous findings that supplementation with β-carotene given orally does not alter serum concentrations of retinol or α-tocopherol. The findings also indicate that β-carotene supplementation, which results in a moderate increase in serum β-carotene concentration, does not significantly change serum concentrations of other carotenoids.