Feb. 22, 2007 -- Eating the raw green vegetable watercress may reduce DNA damage and lower cancer risk, British researchers report.
The University of Ulster's Chris Gill and colleagues say their study "supports the theory" that watercress, eaten raw, may cut cancer risk by curbing DNA damage.
Gill's team studied 60 cancer-free adults, half of whom were smokers.
First, the researchers screened participants' blood samples for levels of antioxidants (nutrients found in many plants, including watercress) and for chemical signs of DNA damage, which may increase cancer risk.
Next, participants were split into two groups.
For eight weeks, each person in the first group ate about 3 ounces of raw watercress daily, supplied by the researchers, in addition to their usual diet.
For comparison, participants in the other group weren't asked to eat watercress.
Afterwards, participants provided more blood samples and took a seven-week break from the study. During that time, they could eat whatever they wanted.
The groups then gave more blood samples and switched their original diet assignments: Those who had been in the comparison group were asked to eat watercress for eight weeks; those who were previously assigned to eat watercress were told to follow their normal diet, with no watercress requirements.
Finally, the participants provided one last set of blood samples.
After sorting through the data, Gill's team found that participants had higher levels of antioxidants and lower levels of chemicals indicating DNA damage in their blood after their eight-week watercress feasting.
That pattern was particularly strong in smokers, the study shows.
Curbing DNA damage might make cancer less likely.
But the watercress study only lasted six months, and cancer typically takes much longer to develop.
So, the study doesn't actually prove watercress prevented cancer in any of the participants.