Is Zoe Harcombe’s advice based on solid scientific evidence?

Person holding a basket of fruit and vegetables
Fruits and vegetables: probably reduce cancer risk

You may have seen an article in the Daily Mail about a new book by Zoe Harcombe on the obesity epidemic.

The article runs through Zoe’s ‘myth-busting’ conclusions.

Looking at her overall message, Zoe basically disagrees with the advice you would get from mainstream health organisations. The result of this is that people are likely to become confused.

This is why it’s unhelpful for this sort of advice to be presented as an authoritative voice.

The article is about obesity generally and not particularly about cancer prevention.

But I thought it would be useful to pick out a couple of her points that do relate to cancer and have a look at what the science actually says.

And the fact is that Zoe’s conclusions that relate to cancer, at least as presented in the Mail, just aren’t supported by the overall body of scientific evidence.

This is why it is best to ignore the advice and stick to credible sources of health information from charities like World Cancer Research Fund (WCRF), or from NHS Choices.

“No evidence for any cancer benefit” from “five a day”

Our 2007 review of the research on cancer prevention was the most comprehensive of its kind ever published.

This found that eating fruit and/or vegetables probably reduces the risk of cancers of the mouth, pharynx, larynxoesophaguslung and stomach.

Our advice was also backed up by a study of half a million people in Europe published this year.

But even aside from any direct effect fruits and vegetables have on cancer risk, they make us feel full and hence helps stop us from overeating.

This means that people who eat plenty of them are less likely to be overweight. This is important because, after not smoking, maintaining a healthy weight is the most important thing you can do for cancer prevention.

“If you do extra exercise, it will be counterproductive because you will get hungry”

Again, this is not right. In fact, the opposite is the case.

Our 2007 Report found convincing evidence that being physically active helps to avoid weight gain and that having an inactive lifestyle is linked with weight gain.

It is true that high levels of activity do increase appetite. But this also means you can eat more calories without gaining weight and the chance of overeating is less than for someone who is inactive.

But another point is that physical activity is not just important for its effect on our weight. Being regularly physically active also has a direct effect on reducing cancer risk.

There is strong evidence that being physically active helps to prevent cancers of the bowel, postmenopausal breast and endometrium (womb lining).

The problem with bad advice

I think it’s a shame Zoe has decided to give this kind of advice.

The likely effect is that people will either follow advice that’s not based on solid evidence or else become confused about conflicting advice.

But the reality is that there will always be people who give quirky health advice that is contradicted by the evidence.

And this is where the Daily Mail comes in.

To be fair, the Mail has made it clear that Zoe’s claims are “controversial”. But I would argue that publishing a big feature about them has given them a credibility that they simply don’t deserve.

There is already enough confusion about dietary advice. It’s a shame that in this case the Mail has decided to publish an article that has added to it.