Beta-carotene and lycopene, but not lutein, supplementation changes the plasma fatty acid profile of healthy male non-smokers

Polyunsaturated fatty acids (PUFAs) are highly susceptible to free radical attack. In vitro studies of carotenoids--including beta-carotene, lycopene, and lutein--have shown them to be effective quenchers of singlet oxygen, t o have good radical-trapping properties, or to be effective peroxyl radical scavengers (sr to have a combination of these qualities), if carotenoids a ct as antioxidants in vivo, then arguably plasma PUM should be conserved. T he objective of the current study was to answer the question "Does suppleme ntation with beta-carotene, lycopene, or lutein, at dietarily achievable le vels, over a time period known to significantly increase circulating carote concentrations, lead to an observable increase in fasting plasma PUFA?" Th e normal diets of human volunteers were supplemented with either 15 mg/day beta-carotene (n = 25), lycopene (n = 23), or lutein (n = 21) for 26 days i n three independent double-blind, placebo-controlled supplementation studie s. Supplementation with p-carotene increased plasma linoleic acid but left the polyunsaturated:saturated (P:S) fatty acid ratio unaltered. In contrast , supplementation with lycopene reduced linoleic acid, which resulted in a large decrease in the P:S ratio, Lutein supplementation had no effect. it w as concluded that neither beta-carotene, lycopene, nor lutein supplementati on engender antioxidant effects that lead to the widespread general conserv ation of plasma PUFAs. beta-Carotene and lycopene supplementation appear to interact with the metabolism of linoleic acid, the "essential" fatty acid, resulting in either an increase (beta-carotene) or decrease (lycopene) in ifs plasma concentration. Alterations in plasma 18:2 or P:S ratios could ul timately lead to changes in tissue cellular membrane composition and hence to alterations in membrane fluidity and cell-surface protein expression.