Daily consumption of watercress, a cruciferous vegetable, may have significant antioxidant effects and reduce damage to lymphocyte DNA, according to a study from Northern Ireland. In the single-blind, randomised study, subjects consumed 85 g of raw watercress daily in addition to their normal diet during the intervention phase. The control group maintained their normal diet. Blood was taken from each group before and after the intervention period. Researchers performed screening of peripheral blood lymphocytes and measured levels of antioxidants for each specimen, and found a significant increase in the plasma concentration of the anti-oxidant β-carotene. They also demonstrated a reduction in basal DNA damage in lymphocytes after challenge with hydrogen peroxide. The effects of watercress consumption appeared to be greater in smokers than in non-smokers.