Also it has been found that watercress seems to raise levels of beneficial substances, whilst cutting levels of harmful ones in the blood stream.
60 healthy volunteers, including 30 smokers, ate an 85g bag of fresh watercress every day for eight weeks in the study and the researchers carried out tests before and after they started this diet.
The cells were also more able to protect themselves from the damaging effects of particles called free radicals.
It was discovered that blood levels of antioxidant compounds, such as lutein and beta-carotene, which help fight the harmful effect of free radicals were increased and at the same time, levels of potentially damaging triglycerides were cut, by an average of 10%.
Other studies in the past have suggested eating increased amounts of vegetables in the cress family such as watercress is linked to lowered incidence of cancer forming.
Head researcher Professor Ian Rowland, currently of the University of Reading, said the study was important because it had people eating watercress in reasonable amounts, which was something that people could do in their lives, as compared with quantities used in laboratory tests.
