Eating lots of fruit and vegetables has only a small effect on warding off cancer, a study published on Wednesday says, although its authors insist that tucking into the recommended "five-a-day" is still good for general health.
Doctors led by Paolo Boffetta at the Mount Sinai Medical Center, New York, pored over eight years of data from a major European investigation into the relationship between cancer risk and food.
The investigation, which is continuing, covers nearly 470,000 volunteers recruited in 10 Western European countries.
Between 1992 and 2000, more than 30,000 of the participants were diagnosed with cancer.
Boffetta's team found that high consumption of fruit and vegetables gave only modest protection against cancer.
An increase of 200 grammes (about seven ounces) a day resulted in a three-percent reduction of cancer risk.
Vegetable consumption by itself also gave a small benefit, although this was restricted to women, while heavy drinkers who ate a lot of fruit and veggies had a somewhat reduced risk, but only for cancers linked to alcohol and smoking.
"The bottom line here is that, yes, we did find a protective effect of fruit and vegetable intake against cancer, but it is a smaller connection than previously thought," Boffetta said in a press release issued by Mount Sinai.
"Any cancer protective effect of these foods is likely to be modest, at best. However, eating fruits and vegetables is beneficial for health in general and the results of this study do not justify changing current recommendations aiming at increasing intake of these foods."
The UN's World Health Organisation (WHO) issued a recommendation in 1990 suggesting that five servings of fruit and vegetables per day helped prevent cancer and other diseases.
"Worldwide, low intake of fruits and vegetables is estimated to cause about 19 percent of gastrointestinal cancer, about 31 percent of ischaemic heart disease and 11 percent stroke," the WHO says on its website.
Ischaemic heart disease is caused by lack of blood supply to the cardiac muscles, typically as a result of artery disease, hypertension, smoking or high cholesterol levels.
The new study appears online in the Journal of the National Cancer Institute, published by Britain's Oxford University Press.