A large body of evidence suggests that a diet rich in antioxidants, which have an anti-inflammatory role [1,2], may contribute to reducing the burden of chronic diseases [3]. Carotenoids are nutrients widely distributed in foods, especially in fruit and vegetables [4], and appear to have antioxidant properties [5,6]. In recent decades, there has been increasing interest in their effects on health; a high dietary intake of carotenoids has been associated with beneficial effects in several systemic diseases [7] and in eye disorders, with protection of the retina from phototoxic light damage [8]. Most studies have focused on lutein (L), a carotenoid with a strong antioxidant effect in vitro [9] that has been associated with a reduced risk of age-related diseases [10]. Lutein is a xanthophyll, i.e., an oxygenated carotenoid that all mammalians, humans included, derive from their diet because they are unable to synthesize carotenoids [11]. Several studies have shown that high L intake, either through diet or as nutritional supplement, has beneficial effects on eye diseases, preventing or even improving both age-related macular degeneration (AMD) [12,13,14,15,16] and cataract [17,18,19,20,21]. However, conflicting data had been reported concerning L efficacy [22,23,24,25,26,27,28,29,30], and in 2006, it was claimed that no compelling evidence had been provided concerning the supposed beneficial effect of L on human health [31]. Furthermore, no univocal data concerning the appropriate dosage for possible L supplementation had been found [32,33,34,35,36,37,38]. More recently, a number of studies have suggested that L may indeed have favorable effects via anti-inflammatory activity [39], improving cognitive functions [40], and decreasing the risk of cancer [41], cardiovascular diseases [39] and other systemic conditions [42,43,44]. Overall, it seems that the amount of L intake, including by supplementation, may partly counter inflammatory processes and favor human health, but inconsistencies still remain.

We reviewed the literature on the evidence for the health effects of L, including its usual intake with different diets, adequate doses, and safety of supplementation, with specific reference to eye diseases.