Measuring oxidative damage in humans: relation to cancer and ageing.

Many uncertainties remain about the free-radical theory of ageing and the role of oxidative damage to DNA in cancer. The chemistry and biochemistry of radical-induced DNA damage are now well characterized in vitro, but the complexity of in-vivo systems leaves this area still largely unexplored. Measurement of thymine and thymidine glycols in urine may be a means of assaying background levels of radical-induced DNA damage in live organisms. Similar approaches may prove useful for testing some of the predictions of the free-radical theory of ageing and of the contribution of free radicals to cancer.