Watercress Reduces Risk of Cancer

21/02/07 Eating watercress daily can significantly reduce DNA damage to blood cells, which is considered to be an important trigger in the development of cancer, University of Ulster scientists revealed (15 February).

The research, published in this month's American Journal of Clinical Nutrition, found that in addition to reducing DNA damage, a daily portion of watercress also increased the ability of those cells to resist further DNA damage caused by free radicals.

The dietary trial involved 30 healthy men and 30 healthy women (including 30 smokers) eating an 85g bag (a cereal bowl full) of fresh watercress every day for eight weeks. The beneficial changes were greatest among the smokers. This may reflect the greater toxic burden or oxidative stress amongst the smokers, as smokers were also found to have significantly lower antioxidant levels at the start of the study compared to the non-smokers.

Professor Ian Rowland, who led the research project, said: "Our findings are highly significant. Population studies have shown links between higher intakes of cruciferous vegetables like watercress, and a reduced risk of a number of cancers. However, such studies don't give direct information about causal effects. What makes this study unique is it involves people eating watercress in easily achievable amounts, to see what impact that might have on known bio-markers of cancer risk, such as DNA damage. Most studies to date have relied on tests conducted in test tubes or in animals, with chemicals derived from cruciferous vegetables."

Prof. Rowland added: "Blood cell DNA damage is an indicator of whole body cancer risk, and, the results support the theory that consumption of watercress is linked to an overall reduced risk of cancer at various sites in the body. The nature of the study group also means that the results are applicable to the general population eating a normal diet."

The single blind, randomised, crossover study was carried out with volunteers aged between 19 and 55. The volunteers ate one daily portion of watercress in addition to their normal diet.

The key findings of the watercress diet are as follows:

-- significant reduction in DNA damage to lymphocytes (white blood cells), by 22.9 percent.

-- reduction in DNA damage to lymphocytes (white blood cells) when a sample was challenged with the free radical generating chemical hydrogen peroxide, by 9.4%

-- reduction in blood triglyceride levels, by an average of 10%

-- significant increase in blood levels of lutein and beta-carotene, which have antioxidant activity, by 100% and 33% respectively(higher intakes of lutein have also been associated with a lower incidence of eye diseases such as cataract and age-related macular degeneration).

Average intakes of dietary fibre, vitamin C, vitamin E, folate and beta- carotene, were significantly higher during the watercress phase of the study.