Not only does watercress make a delightful addition to salads and sandwiches, it can also make a great addition to your anti-cancer arsenal. Daily consumption of fresh watercress daily has been shown to significantly reduce blood cell DNA damage. DNA damage in blood cells is an indicator of a person's overall cancer risk. Watercress contains phenethyl isothiocyanate, also know as PEITC, which is a special mustard oil with significant anti-cancer properties. In addition, these little peppery leaves provide plenty of vitamin C, beta-carotene, and lutein. One study found that consumption of watercress increased test subjects' blood levels of lutein and beta-carotene by 100% and 33%, respectively. Watercress is available in larger supermarkets year round.