Eating double the government-recommended five helpings of fruit and vegetables a day has no effect on whether a woman's breast cancer will come back, a US study has found.
Cancer Research UK said that the finding shouldn't deter women from eating plenty of these foods because they have other health benefits.
But the charity pointed out that there was little evidence that fruit and vegetable consumption, at any level, has a significant effect on the likelihood of breast cancer returning. Evidence suggests that maintaining an active lifestyle and a healthy bodyweight are probably more important.
The study, published in the Journal of the American Medical Association, analysed the effect of diet on nearly 3,100 women who had previously undergone successful treatment for early-stage breast cancer between the ages of 18 and 70.
Half of the participants followed the five-a-day guidelines, while the other half ate nearly double that amount of vegetables and fruits, while also reducing their fat intake to 15 - 20 per cent of their total calorie intake for an average of 7.3 years.
The researchers found that the rates of breast cancer recurrence and mortality were nearly identical for both groups, with 16.7 per cent of women on the high-vegetable diet and 16.9 per cent of those on the regular five-a-day diet experiencing a recurrence of breast cancer during the course of the study.
Commenting on the research, Liz Baker, Cancer Research UK's science information officer, said: "The jury is still out on whether fruit and vegetables can have a role in preventing breast cancer from recurring.
"This certainly doesn't mean that women who have had breast cancer should stop eating fruit and veg - but this study suggests that eating more than the recommended five portions per day doesn't shield a woman from the cancer returning. Further research will help to get a clearer picture."
Ms Baker added that what evidence was available suggested that there was, however, evidence that bodyweight and activity had an effect on cancer recurrence.
"Some studies have suggested maintaining a healthy body weight and staying physically active can improve survival for women who have had breast cancer," she said.
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