Effect of lycopene supplementation on oxidative stress: an exploratory systematic review and meta-analysis of randomized controlled trials.

Exploratory systematic review and meta-analysis of randomized controlled trials in humans. Included participants were diverse, spanning healthy adults and groups such as men with newly diagnosed prostate cancer, people with type 2 diabetes, postmenopausal women, and adults with mildly elevated cholesterol.

Oral lycopene supplementation was evaluated in multiple randomized trials using purified lycopene capsules or beadlets, tomato juice, and Lyc-o-Mato formulations. Doses ranged from 4 mg to 30 mg daily, with treatment periods varying across studies from about 1 week to several months; comparators included placebo, regular tomato juice, or control conditions.

Lycopene supplementation showed a possible benefit for oxidative stress, but the overall biomarker pattern was inconsistent. The clearest pooled finding was a significant reduction in DNA tail length on comet assay, with MD -6.27 [95% CI -10.74, -1.90; P = .006; n pooled = 115], suggesting less DNA damage. In contrast, LDL lag time was not significantly prolonged, with MD 3.76 [95% CI -2.48, 10.01; P = .24; n pooled = 167]. Other oxidative stress biomarkers did not show consistent significant effects, and between-study heterogeneity was very high (I2 = 100% for the pooled outcomes reported).

Evidence was limited by very high heterogeneity, varying lycopene formulations and doses, and substantial differences in populations and study duration. Oxidative stress biomarkers were not standardized across trials, many outcomes were reported in only a few studies, and adverse event reporting was not available in the provided text. The review was exploratory, so the overall certainty for clinical relevance remains limited.