Kiwifruit as a modulator of DNA damage and DNA repair.

Kiwifruit are a rich source of vitamin C and other antioxidants. We have demonstrated the capacity of kiwifruit to protect cellular DNA against oxidative damage in single-dose human experiments and in longer term supplementation trials using the comet assay to measure both DNA-strand breaks and oxidized bases. Enhanced antioxidant status following a single large dose of kiwifruit is shown by an increased resistance of lymphocyte DNA to oxidation by H(2)O(2)in vitro. After 3 weeks (or more) of supplementation, endogenous base oxidation is significantly decreased. In addition to its antioxidant potential, kiwifruit stimulates base excision repair as measured in an in vitro assay with DNA containing 8-oxoguanine as substrate. The relevance of DNA damage protection and modulation of DNA repair to cancer risk is discussed.