So do fruits and vegetables prevent cancer?
You might have seen that last week there was lots of coverage in the media questioning the effect of fruits and vegetables on cancer risk. This would seem to go against our advice to eat plenty of fruits, vegetables and wholegrains for cancer prevention.
So with headlines like “Cancer not fought by Five a Day” and “Five a day will not cut cancer” you might be forgiven for thinking that a study had been published that had found that fruits and vegetables do not reduce cancer risk after all.
But you’d be wrong.
Very roughly speaking, it found that about 2.5 per cent of cancer cases could be prevented if everyone had an extra two portions of fruits and vegetables a day. That might not sound like much, but the reason the percentage is so small is that the researchers have looked at overall cancer cases, when there are plenty of types of cancer where there is no evidence fruits and vegetables reduce risk.
But 2.5 per cent of the total works out as about 7,000 cases a year in the UK, which means that a significant number of cases could be prevented in this way. And as The Sun pointed out, 2.5 per cent is better than the odds of winning £10 on the lottery.
When you consider that this study only monitored people for eight years, which is less time than cancer can take to develop, it means that the real proportion that could be prevented could be even higher. And we also know that people who eat plenty of fruits and vegetables are also less likely to be overweight, which is a separate cancer risk factor.
It is sad that a study that has backed up what the rest of the evidence says about fruits and vegetables – that they reduce risk of cancer – has been reported as having turned the subject on its head. The reason is a press release that has decided to focus on the negative (that the effect is quite small) rather than the positive (that the effect exists).
If you measure the success of a press release in the amount of coverage it generates, then top marks to whoever wrote it. But if you look at scientific press releases and the news articles than come from them as a chance to give people useful public health information, then it’s been an own goal.
Not only is it likely to leave people confused about what the message is for fruits and vegetables, but it is also likely to add to the cynicism about media reporting of cancer. It will also fuel the idea that scientists are always changing their minds about cancer risk, whereas this just isn’t the case.