Watercress lowers DNA damage, cancer risk

The February 2007 issue of the American Journal of Clinical Nutrition published the discovery of researchers in Northern Ireland that consuming watercress is associated with a reduction in DNA damage, which in turn reduces the risk of cancer. Watercress is a member of the cruciferous family of vegetables that includes broccoli and cabbage, which have been associated with a lower risk of several cancers when included in the diet.

Thirty men and women, half of whom were smokers, were randomized to consume their usual diet or receive the addition of 85 grams raw watercress daily for eight weeks. After a seven week period in which no watercress was consumed, the subjects switched regimens for an another eight weeks. Fasting blood samples were collected at the beginning and end of each eight week phase of the trial and several measures of lymphocyte DNA damage assessed. Plasma lutein, retinol, alpha-tocopherol and beta-carotene levels were also measured.

Significant reductions in DNA damage occurred when the participants consumed watercress. These reductions were of a greater magnitude in smokers. Plasma lutein levels doubled following watercress supplementation, and beta-carotene concentrations rose by approximately one third, although the increase proved to be greater among nonsmokers.

Watercress may exert its protective effect on the genes due to its rich antioxidant content, in particular, lutein and beta-carotene. Analysis of watercress leaves detected several phenolic components such as rutin, as well as a number of glucosinolates, which may also contribute to its protective effect. The difference in beta-carotene levels between smokers and nonsmokers in this study could be due to a greater requirement of the vitamin by individuals who smoke. The authors conclude that their findings "provided important evidence that supports the hypothesis that consumption of watercress, a cruciferous vegetable, can reduce cancer risk in humans via a decrease in DNA damage."