A dose-response study on the effects of purified lycopene supplementation on biomarkers of oxidative stress

Objective: While tomato product supplementation, containing antioxidant carotenoids, including lycopene, decreases oxidative stress, the role of purified lycopene as an antioxidant remains unclear. Thus, we tested the effects of different doses of purified lycopene supplementation on biomarkers of oxidative stress in healthy volunteers. Methods: This was a double-blind, randomized, placebo-controlled trial, examining the effects of 8-week supplementation of purified lycopene, on plasma lycopene levels, biomarkers of lipid peroxidation (LDL oxidizability, malondialdehyde & hydroxynonenals (MDA & HNE), urinary F₂-isoprostanes), and markers of DNA damage in urine and lymphocytes. Healthy adults (n = 77. age ≥ 40 years), consumed a lycopene-restricted diet for 2 weeks, and were then randomized to receive 0, 6.5. 15, or 30 mg lycopene/ day for 8 weeks, while on the lycopene-restricted diet. Blood and urine samples were collected at the beginning and end of Week 2 of lycopene-restricted diet, and at end of Week 10 of the study. Results: Independent of the dose, plasma lycopene levels significantly increased in all lycopene supplemented groups versus placebo (p < 0.05). ANOVA revealed a significant decrease in DNA damage by the comet assay (p = 0.007), and a significant decrease in urinary 8-hydroxy deoxoguanosine (8-OHdG) at 8 weeks versus baseline (p = 0.0002), with 30 mg lycopene/day. No significant inter- or intra-group differences were noted for glucose, lipid profile, or other biomarkers of lipid peroxidation at any dose/time point. Conclusions: Thus, purified lycopene was bioavailable and was shown to decrease DNA oxidative damage and urinary 8-OHdG at the high dose.