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

Fruits and vegetables: probably reduce cancer risk
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 cancers of the mouth, pharynx, larynx, oesophagus, lung 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.


26 thoughts on “Is Zoe Harcombe’s advice based on solid scientific evidence?”

  1. Dear Richard – many thanks for replying to my email – your copy of “The Obesity Epidemic: What caused it? How can we stop it?” is in the post. I didn’t feel that I could leave the accusations here unchallenged in the interim.

    The point on five-a-day is that there was no scientific evidence at the time it was created. Five-a-day started as a “National five-a-day for better health” program in 1991 as a public-private partnership between the American National Cancer Institute (NCI) and the Produce for Better Health Foundation.
    The programme started in California and it has spread across more than 25 countries and five continents. Five-a-day has since been trademarked by the National Cancer Institute. It is a marketing campaign, not a science based initiative.

    The Produce for Better Health Foundation can be found at the web site “” and their purpose is to get us to eat more fruit and vegetables. The sponsors of the Produce for Better Health Foundation are companies with an interest in selling more fruit and veg, from logistics firms to specialist producers to insecticide companies.

    I understand that there has been an attempt to post rationalise the idea that there may be some benefit, but there was no evidence at the time the campaign started. It is reasonable for the public to think that such a widespread campaign would have been founded on sound evidence. I am merely pointing out that this is not the case.

    The most recent analysis failed to retrospectively find any evidence for benefit for cancer. In April 2010 a study was published in the Journal of the National Cancer Institute written by Paolo Boffetta, as the lead of a large group of European researchers. The study sought to quantify if cancer risk were inversely associated with intake of fruit and vegetables. The article analysed data from the EPIC (European Prospective Investigation into Cancer) study, involving 142,605 men and 335,873 women for the period 1992-2000. This review of almost half a million people found that eating five portions of fruit and vegetables a day had little effect on cancer risk and the very small difference observed could be explained by other factors. The study also grouped participants into five categories from the lowest intake of fruits and vegetables (0 to 226 grams a day) to the highest intake (more than 647 grams a day). Significantly, the cancer risk did not vary between the five groups. The overall conclusion of the study was that: “A very small inverse association between intake of total fruits and vegetables and cancer risk was observed in this study. Given the small magnitude of the observed associations, caution should be applied in their interpretation.”

    Please also bear in mind that I work exclusively in the field of obesity – five-a-day was never intended to help obesity and for many reasons it is making the problem worse. Fructose is called the lipogenic carbohydrate in the world of obesity for good reason – it goes straight to the liver to be metabolised where it is invariably turned into fat. Fructose (especially eaten 5 times a day) is also keeping the body in a fat storing state and is extremely unhelpful in our drive to avoid type 2 diabetes.

    Veg are OK – if eaten with fat (like butter) to deliver the fat soluble vitamins, but fruit is really not very nutritious when compared with animal foods like meat, fish, eggs and dairy products (or non-animal products like sunflower seeds). We have assigned a halo effect to fruit that is simply not justified.

    I discuss conflicts of interest a great deal in the book and of course there was a conflict of interest from the conception of five-a-day. I notice that the WCRF has Dole, Apple a day and South African fruit as corporate partners and promotes Fruity Friday. Whatever the product, this is a conflict of interest. To Dr Robert Lustig and Dr Richard Johnson, the world leaders in the metabolism of fructose, there is little difference between fruit juice, fizzy drinks and alcohol in terms of how they are metabolised by the body.

    On the exercise point, it is difficult to get an entire book chapter across in one bullet point (written by a journalist) in a newspaper. My views on this are:
    Just as I think humans should eat naturally (meat, fish, eggs, dairy, vegetables, salads, nuts & seeds. Fruits and whole grains should be eaten in moderation if overweight or needing to manage weight) so I think that humans should move naturally (walk, talk, sing, dance, cook, clean and tend the land.) I do not think that running marathons and spinning classes are natural or necessary. Man’s survival thus far has depended as much on us conserving energy as it has on us gathering energy.

    For general health therefore I think that humans should be naturally active rather than pursuing unnatural exercise. Natural activity is an excellent thing to do for general health and well being. The point on obesity is simply one of relativity – it is a fact that we can eat in one minute what could take an hour to use up. The importance of NOT putting something in our mouths in the first place is therefore paramount. We can’t get fat watching TV – we have to eat something to get fat.

    Hence I cannot support attempts to ‘overcome’ the obesity epidemic with exercise – we have to correct WHAT humans are eating (not even how much, but what) to overcome obesity. The Deakin study showed that sedentary behaviour did not cause this epidemic and exercise will not cure it.

    I trust that you will respect my right to reply and that you enjoy the book and see that this is just the tip of the iceberg in terms of dietary myths that need to be debunked.
    Very best wishes – Zoe Harcombe

  2. just wanted to say i take great exception to the following comment from above.
    “This is why it’s unhelpful for this sort of advice to be presented as an authoritative voice.”

    people should be confused since they have been lied to for years and years about whats best for them.
    i have read many many books on this subject and look forward to reading zoe’s, i have also suffered from weight problems and since reading and becoming educated about these things have lost 2.5 stone in weight.
    just because the world has been blinded by the many people who make a fortune out of the health food industry is no reason someone with genuine knowledge should not speak up.

  3. The fact is people need to look at ALL research done in that field, and considering what the general consensus is when only taking into consideration the high quality, robust and reliable studies. The health authorities base their health advice on this at all times and so do other reliable sources of information i.e. WCRF.

    Thank you WCRF for putting the article out there.

  4. Nice article.

    In response to Zoe’s statement
    “I do not think that running marathons and spinning classes are natural or necessary. Man’s survival thus far has depended as much on us conserving energy as it has on us gathering energy”

    Humans evolved as persistence hunters in desert environments (this activity is still observed in small tribes). This often requires running for upwards of 6 hours a day. Thus running is entirely natural. This is one of the reasons humans have the most efficient thermoregulatory system in the animal kingdom, and are the best endurance animals out there.

    I would therefore suggest that running is entirely natural!
    But hey, what do I know, I’ve only got a PhD in environmental physiology and I’m not trying to sell anything…

    I recommend you read some of Timothy Noakes work from the University of Capetown, or Daniel Lieberman from Utah.

  5. Without going into the problems of cherry-picking science to suit your thesis, or the problems of not understanding the role of epidemology (both dismissing it as Zoe does, or as she does point out, mistaking it for meaning that it proves causality) – both things which publishing a few peer-reviewed articles and doing a PhD in a reputable university should sort out, Zoe’s comment that the Five-a-day campaigns are industry funded is correct. They are. And they’ve been based on science suggesting that a diet rich in fruit and vege is good for health. Given the limited public purse, it’s necessary for industry to fund such initiatives. They would not get any backing from public health authorities if the science wasn’t there though. Advertising watchdogs would be on them like terriers possesed. The science might be a bit mixed and not always clear cut (in nutrition it rarely is), but if you’re going to compare like with like, and discourage the intake of fruit – which will invariably be replaced by something else sweet, such as a chocolate bar, then you’re just being irresponsible.
    And while yes, a bit of fat does help lipid soluble vitamin absorption, you’re digestive system is an incredible thing (provided it’s not a mess due to a lack of dietary fibre) and will adapt so your body can pull out the nutrients it needs – it’s been proven many times in bioavailability studies. And in the western diet, there’s not normally a shortage of fat either.
    The fructose issue – it’s still a fairly new hypothesis, and you’ve got to consider the difference between eating a self-controlling amount of fructose via fruit (bulk is important here), and getting unusually high intakes via soft drinks and the like.
    So Zoe, I give you every encouragement to go ahead with your PhD in nutrition science, so you can debate and learn with your new colleagues and peers, learn to see the totality of the evidence, and find out why nutrition science is not so straight forward, making it one of the at times most frustraiting, but ultimately rewarding fields of science to work in.

  6. Regarding the ‘Fructose Hypothesis’ please go and investigate, at a biochemical level, how fructose is metabolised.

  7. Richard Evans is a PR man and on the WCRF site is described thus:-

    As Head of Communications, Richard can talk about the general messages of WCRF,

    There’s no disgrace in that but nothing in his piece challenges the actual science. He just makes unsubstantiated statements or ‘comments’ as his job description says. The key to Zoe Harcombe’s messages is that she goes to the scientific origins of numerous studies and ‘facts’ and examines the results and scientific interpretations not the amateur summaries of unqualified journalists. She also notes the commercial interests of the academics taking part in the studies and looks for bias towards such interests. Richard v Zoe? Not hard is it?

  8. Fruits contribute to obesity? Hmmm, how many obese people actually eat a lot of fruits (and commercial fruit juices and Newton figs do not count as fruits)?

  9. Just to add to the debate – Marathons are bad for your health! they eat into your healthy muscle tissue stores after your glycogen reserves are exhausted and can do structural damage to joints and ligaments. (although I am an ex marathon runner)

    Also, Fruit contains a simple carbohydrate, which raises insulin levels, (fat producing hormone). If that energy isnt being used it will be stored as fat.

    Visible fat is stored as Triglycerides, which is made up of 3 fatty acids and one Glycerol. In that form, accumulated fat cannot be be used or reduced. Where carbohydrates are present, any dietary fat eaten as part of a meal, will automatically be stored.

    The only question I have for Zoe (I have bought her book and think its a eyeopening and strongly researched) is, what about fibre? I believe fibre ate in fruit is important for lowering cholestorol, the anti-oxidants it contains and clearing for out your bowels. So can you please address this point? I believe that these benefits from eating fruit are definitely a benefit of eating fruit *as well as the vitamins they contain.

    Also, You stated in your book that you find it hard to believe that people actually enjoy doing exercise, and I confirm that this is not the case. I live for running and it gives me mental clarity, It also releases feel good hormones and burns energy! Given that it also trains your heart and lungs and can help with weight loss, it can definitely reduce some of the risk factors associated with CHD.

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  12. The point is that Zoe is changing people’s health for the better, and I’m sure that also has a lot to do with the fact that the foods she is suggesting for health, help in preventing inflammation, Candida and many other things. This is turn only helps to avoid cancer. Much of her food knowledge is shared by The Weston A. Price Foundation and is supported by scientific studies which were done outside of corporation funding (and a conflict of interest). She exercises every day so the nitpicking about the amount of exercise is just that. I feel that we should listen to those that are producing truly measurable results. When the World Cancer Research Organization and many other Cancer organizations start to produce a high percentage rate of success– and by that I mean 75% or more of people who’ve beaten cancer because of their recommendations, then I would start listening closely to their advice. As of now, I haven’t seen any evidence of this and I’m seeing healthier people in the communities who are eating and living by Weston A. Price principles and basic traditional food principles while remaining active. The proof of what is true is in the results!

  13. If we start with the evidence – eg The USA and the UK populations are in the midst of an obesity epidemic – and that this is of recent origins, it would seem starkly evident that the current official nutritional advice is simply failing. A conversation I had last night with a GP (ie doctor) friend of mine seemed to simply implicate a modern sedentary lifestyle. I did not go on to explore whether this was simply an abdication of the problem to avoid an “active discussion” in the wrong environment.

    If we put aside the politics and the undoubted complexities of unhealthy vested interests we are, I suggest, left with a scientific approach. The first principle is that of observation and we see a seemingly out-of-control obesity epidemic. We also note that nutritional advice relating to obesity has remained essentially unchanged for a couple of decades while the obesity has been growing substantially. Even if the advice was well intended at the time, when the facts change you can change the advice. So that seems a plausible action.

    There is a fascinating parallel to be drawn comparing big food and beverage companies with tobacco companies and alcohol companies. One day we decided tobacco was bad for us so we taxed smokers and then successfully sued the tobacco companies for killing some of us. We also allow them to carry on now that we know tobacco is bad for us. Alcohol is not dissimilar but it’s nice to have a tipple and it doesn’t effect other people much (in the big scheme, and unlike smoking which made other peoples clothes smell and caused secondary deaths)so we just tax alcohol to keep it in check. However apparently it’s fine to allow food companies to put sugar, additives, horsemeat (oh yes, that’s actually probably safe)into just about everything that most people can afford to buy. We already know that sugar is simply bad for you and it’s role in obesity will eventually be forced to be admitted by the food companies and acted upon. It is no less a form of legalised poisoning than tobacco or alcohol. Obesity and related diseases and conditions can be fatal. Simple re-branding of large burger chains does not make the food any better, it just feels more modern and if the skin changes they can kid us the rest has changed too. As we have seen over the past few years, the world is now run by large, strong corporates and not by weak governments.

    The other area of research which is developing apace is that of the role of the human biome. It is an influence which has the potential to overturn the emphasis of modern medicine. It will not be able to do so until we have a new generation of medics capable of breaking free from traditional views and teachings and indeed the science is young and so lacks any efficacy at this time (I hope I am wrong and we are making faster strides). Diet subtly altering the balance of the biome ( and its direct effects and effects on our own genetic expression) is implicated in a number of effects from obesity and diabetes to allergies etc. There is a chance that when we have a fuller understanding of the role of the biome and it’s influences we will understand why the balance of chemicals and nutrients we call food affects us so profoundly.

    In the meantime there is no need to do nothing. We don’t know how to cure cancer but it does not stop us working to prevent it. At the same time it is arguable that big food business is keeping the oncologists, and others, in work with their sugar-coated everything.

    Bottom line is – I applaud Z Harcombe for upsetting applecarts. Taking on both the establishment and big biz is an important part of our democracy. I sense she will also be proved correct – it’s just a question of this century or next and how many people are permitted to suffer in the meantime.

  14. Zoe is right actually. If you eat a wide variety of vegetables, you don’t get much added benefit from fruit. It’s lots of sugar for little benefit. I think we are all better off replacing sweet fruits with more greens. Sure an apple here and there is fine, but grapes and watermelon and so forth, what do they give you that a wide variety of vegetables don’t? Sugar. There is NO evidence that eating fruit reduces cancer risk, IF you eat vegetables.

  15. Zoe makes a lot of claims about things that were not known “at the time” of studies, but that is a qualifier that negates results. she also touts the nutrition of meats without looking at studies that clearly indicate that the protein and fat significantly contribute to cancer risks. She claims to work with obesity, but I didn’t see anything in her writing about the fact that eating animal products including their cholesterol as contributors to obesity. Implicating fruits for obesity is ludicrous. Yes drinking high amounts of processed fruit juice, concentrating fructose adds extra sugar that is converted to fat if in excess, however, eating fruits does not cause obesity. She also does not look at other things eating to contribute to both cancer and obesity. If one eats carcinogens and then eats non carcinogens, the non carcinogens will not necessarily stop caner. If one eats a high fat meat and dairy diet and supplements it with fruits and vegetables, the high fat carcinogenic intake has been shown to be the cause of both obesity and cancer. Claims she makes are not founded. Her science is half science at best.

  16. Zoe’s advice on exercise is laughable.

    “so I think that humans should move naturally (walk, talk, sing, dance, cook, clean and tend the land.)”

    Why? What’s the rationale behind this requirement for “natural” exercise? Why is running considered “unnatural” somehow? Not only are our ancestors nomadic hunters and running was vital for their way of life, but also we know that intense exercise helps to not only reduce fat stores but also prevents further fat from being stored in your body.

    Unfortunately Zoe is just out there trying to drum up support for her crappy book so that she can con people into buying it…of course people want to hear “you don’t have to run” and “you don’t have to eat less”, but unfortunately it’s not true.

  17. Zoe is correct about “the facts she studies” and writes about. God bless her for all she does to take away the confusion and lies we have all been preached to by money greedy people and companies that do not care one jot about health. There is not one animal in the wild that would run for miles and miles for fun or lift heavy wights either. The animals that are very strong or fast or can run for miles like hyenas, evolved to do so out of a necessity to survive. The only fat animals in the wild are conditioned by nature usually because of hibernation and such. We are fat because of greed by nature and the manufactured crap we have been manipulated into eating by society, plus all the wrong information and advertising by greedy companies. It would not have been good for us to be fat or lazy in the wild. we would have been extinct long ago. Refined carbs eaten in abundance will make you fat and ill. The best exercise are those that we’re designed by nature, lifting, stretching, jumping, running, climbing, walking and getting out of breath on a regular basis but not for hours on end. Unless you want to be an athlete. But then you would have to watch what you eat even more carefully. And i don’t think the’re are any animals in the wild eating five a day. Where is there an environment in the wild with all these fruits and veggies in one place for an animal. Man has brought them together partly for survival but mostly for monetary reasons. Zoe Harcombe does all her work out of integrity, love and kindness. luckily she can flog her info in book form in order to make a living which we all have been forced to do buy society. She has more balls and integrity the most people have.

  18. Zoe has every right to and makes some very valid points which deserve to be heard, (and challenged if proved wrong). Everyone seems to ignore the facts of how we have been subjected, for 50 years, to a massive dietary experiment based on an unproven, unscientific Theory. Although the basis of that theory has been now disproved, the dogma remains set in stone by the dietary advice pushed out by the authorities. The food giants, namely the Sugar and Corn Oil industries used this to generate big money and perpetuate the dogma by brainwashing everyone with their implied “healthy” slogans.
    These products (highly polyunsaturated vegetable oils and Sucrose/HFCS), if you think about it, never existed in the food available until the industrial revolution, so I fail to understand how they can claim them to be healthy in the quantities now incorporated in the processed foods they now encourage us to buy.
    To condemn what she is saying, when the long term implications of the major dietary change has never been tested or questioned. is crazy. She is stating what seems obvious to me when you apply the metabolic knowledge we have now to the various food types.
    In this light, the fruit conundrum is obvious. In our natural environment we would NOT have fruit in our diet 365 days of the year! September would bring the fruit harvest for a month or so and that would be it and fructose is metabolised into fat by the liver for storage.
    Bottom line is that if our diet is dramatically different to our ancestral norms, high glycaemic carbs are mainly man made, so who can categorically state that our diet is not contributing to the Obesity, Diabetes and Cancer which the WCRF is trying to refute!
    Keep up the good work Zoe.

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