Beware extreme diets, cancer patients warned

Cancer survivors who adopt "extreme diets" to try to stop the disease returning are wasting their time and may even be harming their health, experts warn.

Dietary regimes which urge cancer patients to drink only fruit and vegetable juice, avoid meat or dairy products or take large doses of supplements may be popular, but will not work, according to the World Cancer Research Fund.

A significant, but unknown, number of the 2 million Britons who have been diagnosed with some form of the disease turn to alternative diets in a bid to prevent a recurrence once they have been given the medical all-clear, cancer charities say.

Dr Rachel Thompson, science programme manager at the WCRF, which is renowned for its research into preventing the disease, said: "People who have had cancer … often end up following diets that involve doing things like cutting out types of food or having lots of supplements. It is very easy to make bold claims about how different diets can stop cancer returning, but there is no strong evidence these diets do what they say. People are often investing money and hope in something that could be doing more harm than good."

Some websites, doctors, nutritionists and private treatment centres endorse particular, expensive, diets which they claim can help to beat cancer. But research showed that taking high doses of certain supplements could be harmful, said Thompson. "If a cancer survivor is cutting out food groups then it may be that they become underweight, which could mean they are more susceptible to infection."

Macmillan Cancer Support, which gives practical help to cancer patients, said that some diets were so imbalanced they could harm a patient's treatment by affecting the result of a blood test.

It acknowledges how importance diet plans are to cancer patients, but advises caution when adopting an alternative diet, often vegetarian or vegan, which claims to rid the body of toxins. A spokeswoman, Anna Brosnan, said that while healthy eating could reduce the risk of cancer reappearing, such diets did not extend a cancer sufferer's life. "There is no scientific evidence that cutting out key elements of a normal diet will improve the outcome for people once they have cancer."

Macmillan particularly criticises the Gerson therapy, which claims to cleanse the body and boost metabolism. Some people who have followed it have ended up with nausea, a perforated colon, vomiting and infections from the enemas involved.

The warnings come as the WCRF prepares to launch on Wednesday the first evidence-based dietary and lifestyle guide for patients trying to stop cancer returning. Eating Well and Being Active Following Cancer Treatment will be available free from the charity's UK website. It says "dietary and lifestyle approaches to prevent cancer do not have to be extreme. They do not require you to cut out key food groups, consume special foods, take vitamin supplements or spend a lot of money."

Organic food is no more likely to reduce the risk of cancer than non-organic produce, says the WCRF. Some high-dose supplements "can increase the risk of cancer ... and can have unpredictable and harmful effects", the new guide adds.

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