The research, unveiled at a press conference today (14 September 2010), shows that the watercress compound is able to interfere with the function of a protein which plays a critical role in cancer development.
As tumours develop they rapidly outgrow their existing blood supply so they send out signals which make surrounding normal tissues grow new blood vessels into the tumour which feed them oxygen and nutrients.
The research, led by Professor Graham Packham of the University of Southampton, shows that the plant compound (called phenylethyl isothiocyanate) found in watercress can block this process, by interfering with and 'turning off' in the function of a protein called Hypoxia Inducible Factor (HIF).
Professor Packham, a molecular oncologist at the University of Southampton, comments: "The research takes an important step towards understanding the potential health benefits of this crop since it shows that eating watercress may interfere with a pathway that has already been tightly linked to cancer development.
"Knowing the risk factors for cancer is a key goal and studies on diet are an important part of this. However, relatively little work is being performed in the UK on the links between the foods we eat and cancer development."
Working with Barbara Parry, Senior Research Dietician at the Winchester and Andover Breast Unit, Professor Packham performed a pilot study in which a small group of breast cancer survivors, underwent a period of fasting before eating 80g of watercress (a cereal bowl full) and then providing a series of blood samples over the next 24 hours.
The research team was able to detect significant levels of the plant compound PEITC in the blood of the participants following the watercress meal, and most importantly, could show that the function of the protein HIF was also measurably affected in the blood cells of the women.
The two studies, which have been published in the British Journal of Nutrition and Biochemical Pharmacology, provide new insight into the potential anti-cancer effects of watercress, although more work still needs to be done to determine the direct impact watercress has on decreasing cancer risk.
Watercress Alliance member Dr Steve Rothwell says: "We are very excited by the outcome of Professor Packham's work, which builds on the body of research which supports the idea that watercress may have an important role to play in limiting cancer development."
A summary of the research has been accepted for inclusion in the Breast Cancer Research Conference which is taking place in Nottingham from 15 to 17 September.
Breast cancer is the most common cancer in women in the western world and currently affects approximately 1 in 9 women during their lifetime.