Plant carotenoids and related molecules: important dietary antioxidants.

The antioxidant effects of dietary carotenoids such as beta-carotene have been well documented in various systems in vitro, using either organic solvents or membrane systems. However, the biologically relevant studies of the effects of beta-carotene on low-density lipoprotein (LDL) oxidation are still controversial, as are those studies using LDL from individuals supplemented with large amounts of beta-carotene. These findings do not agree with the epidemiological evidence which suggests that individuals who consume fruits and vegetables rich in carotenoids, or who have relatively high serum carotenoid levels, are at a lower risk of developing coronary heart disease. What is apparent is that studies that have looked at antioxidant protection in the whole organism have demonstrated a decrease in markers of lipid peroxidation after beta-carotene supplementation. Maybe those studies trying to pin-point the antioxidant site of carotenoids in vivo have been looking at the wrong tissue.