Watercress (Nasturtium officinale R. Br.) and other plants of the Brassicaceae family including cabbage, broccoli, cauliflower, Brussels sprouts, kale, mustard greens, collard greens, bok choy and turnips contain specific indoles that activate enzymes in the body that deactivate and dispose of excess estrogen thereby reducing the risk of several serious conditions.

Indole-3-carbinol accelerates estrogen deactivation by about 50% at 500mg per day. Heavy cooking destroys indoles and is not recommended for medicinal purposes. The German Commission E recognizes watercress for addressing respiratory congestions, especially cold-related runny nose and coughs.

In Europe, watercress is popular as a blood cleanser and is contained in several phytopharmaceutical choleretic preparations (a choleretic increases the flow of bile into the intestines). The fresh leaves are a superior food medicine containing high levels of vitamins A, C, and iodine. Its calcium is also well assimilated by the human body, and the herb has been traditionally used as a remedy for vitamin and mineral deficiency.

Watercress is now well recognized for helping to prevent lung problems in smokers. In a study of smokers who consumed a diet rich in watercress, the levels of toxic compounds were reduced. Other compounds in watercress, including mustard oil glycosides (glucosinolates), specifically gluconasturtiin, which can be hydrolyzed to 2- phenethyl isothiocyanate (PEITC) are known to have cytotoxic activity and activate detoxification enzymes in abnormal cells, thereby reducing their growth.