Doubts on fruit and veg cancer diet

Research on almost 500,000 people found eating five portions of fruit and vegetables a day (about 400g) had little effect on cancer risk, as did eating more or fewer portions.

While there is evidence of a "small" protective effect of fruit and vegetables, the chance a reduced risk could be caused by something else cannot be ruled out, the researchers said.

The new research was carried out by experts who analysed data from 23 centres in 10 European countries who were part of the European Prospective Investigation into Cancer and Nutrition (EPIC).

In the UK, centres at Cambridge and Oxford were included in the study, which looked at cancer risk between 1992 and 2000.

People's daily consumption of fruit, vegetables and fruit and vegetables combined was analysed and matched against data on the number of cancers.

Researchers adjusted the results for other factors likely to influence the results, such as smoking, alcohol intake, obesity, meat and processed meat intake, exercise and factors specific to women, such as if they had ever taken the Pill or hormone replacement therapy.

People were sorted into five groups, from those with the lowest intake of fruit and vegetables (0 to 226g a day) to those with the highest (more than 647g a day).

The results showed that regardless of which group people were in, if everyone ate an extra 200g of fruit and vegetables a day, the overall reduced risk of cancer was three per cent.

Eating an extra 100g of vegetables a day decreased the risk by about two per cent while an extra 100g of fruit a day reduced the risk by about one per cent.

The link between eating a large amount of vegetables and reduced cancer risk only applied to women, the study found. And while heavy drinkers had a reduced risk from eating lots of fruit and vegetables, this reduction only applied to cancers caused by alcohol or smoking.

Further analysis showed if everyone in the sample ate an extra 150g a day of fruit and vegetables, 2.6 per cent of cancers in men and 2.3 per cent of cancers in women could be avoided.

The findings contradict a 1997 report from the World Cancer Research Fund (WCRF), which said there was "convincing evidence" of a protective effect against respiratory and digestive cancers from eating large amounts of fruit and vegetables.

The latest research, led by Paolo Boffetta, from the Tisch Cancer Institute at Mount Sinai School of Medicine in New York, was published in the Journal of the National Cancer Institute.

The researchers concluded the link between reduced cancer risk and fruit and vegetables intake was "very weak" and the link with other possible factors cannot entirely be ruled out. But scientists still recommend five-a-day since, at the very least, this will help combat obesity, a major risk factor for cancer.

WCRF science programme manager Dr Rachel Thompson said: "This study suggests that if we all ate an extra two portions of fruits and vegetables a day (about 150g), about 2.5 per cent of cancers could be prevented.

"Given the fact that there are many types of cancer where there is no evidence eating fruits and vegetables affects risk, it is not surprising that the overall percentage is quite low.

"But for the UK, this works out as about 7,000 cases a year, which is a significant number.

"If you look at specific types of cancer, including mouth, pharynx and larynx, stomach and oesophagus, the evidence shows that eating plenty of fruits and vegetables probably reduces risk. Even if fruits and vegetables did not directly reduce risk, it would still be a good idea to eat them because people who eat plenty of fruits and vegetables are less likely to become overweight.

"Scientists now say that, after not smoking, maintaining a healthy weight is the most important thing you can do for cancer prevention."