SOY beans or seaweed? Broccoli or blueberries? Grapefruit or green tea?
Digesting the science behind foods that fight cancer is a minefield of conflicting advice. One week, research reveals certain foods can slow cancer cell growth. The next, the same food is found to fertilise tumours. For those diagnosed with the disease, deciding what to eat to optimise chances of recovery has never been more confusing.
Antioxidant-rich foods such as sweet potatoes, carrots and green leafy vegetables have long been thought to protect against cancer by stabilising molecules, known as free radicals, which can cause damage to cells. However, a Harvard Medical School report last year found antioxidants could help cancer cells to thrive - although Australian cancer specialists warned that the results had been found in a laboratory, not in human trials.
Similarly, research on the protective effects of soy products against breast and prostate cancer has been met with evidence that soy-based supplements may be risky for people taking conventional cancer drugs.
Trying to ease confusion, the World Cancer Research Fund released two reports, in 2007 and last year, providing the most comprehensive review ever of scientific evidence on diet, lifestyle and cancer prevention. More than 7000 studies were reviewed by 200 scientists.
The main findings were that people with the disease should follow the same advice as those trying to prevent cancer - exercise for 30 minutes a day, choose mainly plant-based foods, limit red meat and avoid processed meat. They also found that fatty food was not found to be a cancer risk in itself, but weight gain associated with it was.
Jenelle Loeliger, senior dietitian at the Peter MacCallum Cancer Centre, said the popular belief that sugar fed cancer was also found to be baseless. ''Tumours don't have a preference for a particular nutrient or a type of food,'' she said. ''The evidence shows that cancer will take all the nutrients that it wants from whatever food is sitting in that person's body.''
The report stressed that diets to prevent cancer recurring ''do not require you to cut out key food groups, consume special foods, take vitamin supplements or spend a lot of money''.
However, many practitioners in alternative and mainstream medicine argue that saying there is not sufficient evidence some foods can increase survival odds is not the same as saying there is evidence that it does not work.
French psychiatrist David Servan-Schreiber, who wrote international bestseller Anticancer: a new way of life after being diagnosed with brain cancer, found the main difference between populations with the highest cancer rates and the lowest was diet.
For example, he said it was not surprising Indians had much lower rates of lung, colon, breast and kidney cancer than Westerners, given their diet has high levels of turmeric, a spice known to act as an anti-inflammatory and prevent tumours in mice.
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