It has been observed that there is an inverse relationship between dietary or serum lutein levels and risk for age-related macular degeneration and cataracts. There are also amounting evidences suggesting that dietary antioxidant vitamins are positively associated with lung function and enhancing heart function.

In the study published in July 2001 [Q.Y. Lu, et al. July, 2001. Inverse associations between plasma lycopene and other carotenoids and prostate cancer. Cancer Epidemiol. Biomarkers Prev. 10(7):749-56.], the authors performed a case-control study to investigage the effects of plasma lycopene, other carotenoids, and retinol, as well as alpha- and gamma-tocopherols on the risk of prostate cancer. The study included 65 patients with prostate cancer and 132 cancer-free controls: all of them were interviewed using a standard epidemiological questionnaire at the Memorial Sloan-Kettering Cancer Center from 1993 to 1997. Plasma levels of carotenoids, retinol, and tocopherols were measured by high performance liquid chromatography. An unconditional logical regression model was employed in bivariate and multivariate analyses using Statistical Analysis System (SAS). After adjusting for age, race, years of education, daily caloric intake, pack-years of smoking, alcohol consumption, and family history of prostate cancer, significantly inverse associations with prostate cancer were observed with plasma concentrations of the following carotenoids: lycopene [odd ratio (OR), 0.17; 95% confidence interval(CI), 0.04-0.78%; P for trend, 0.0052]and zeaxanthin [OR, 0.22; CI, 0.06-0.83; P for trend, 0.0028] when comparing highest with lowest qualities. Borderline associations were found for lutein [OR, 0.30; 95% CI, 0.09-1.03; P for trend, 0.0064] and beta-cryptoxanthin [OR, 0.31; 95% CI, 0.08-1.24; P for trend, 0.0666]. No obvious associations were found for alpha- and beta-carotenes, retinol, and alpha- and gamma-tocopherols. The study confirmed the inverse associations between lycopene, other carotenoids such as zeaxanthin, lutein, and beta-cryptoxanthin, and prostate cancer.