High fruit and vegetable intake `can help to prevent cancers'

Some of the most common cancers are preventable, and simply changing the diet can play a pivotal role in reducing the risk of succumbing to them, according to a leading British nutritionist.

To get the preventive benefits from foods, however, would probably require most people in the developed world to double their daily fruit and vegetable intake, said Dr Sheila Bingham, of the Dunn human nutrition unit at Cambridge University.

While it might seem a dramatic increase and had implications for farming practices, it could be done. Those consuming the "Mediterranean diet" were already eating three times more fruit and vegetables than diets in northern Europe.

Colorectal cancer is the second most common cancer in Britain [and Ireland], with the most recent studies suggesting 80 per cent of cases are attributable to diet. "This means that it is potentially a preventable disease," she told an international meeting of the Biochemical Society in University College Cork.

Research was confirming that high rates of cancer in the colon/large bowel were associated with populations consuming large amounts of meat and animal fats but also having diets low in starch, certain types of fibre and vegetables.

Some studies were suggesting that increased consumption of red meat was increasing cancer risk but the reasons for this were not clear. Dr Bingham advocated a reduction in meat consumption along with increased fruit, vegetable and cereal intake.

Indications of the diet-cancer link were confirmed by sharply differing cancer rates throughout the world that could not be attributed to genetic factors. When people move to Ireland or the US, for example, particular cancer rates increase. "There is some environmental factor at play; food is the strongest contender." Eastern diets noted for their high levels of fruit, vegetables, fish (because they contain the right kind of fats) and soy sauce (containing beneficial anti-cancer plant hormones known as phyto-oestrogens) had correspondingly low rates of diet-related cancers, particularly breast and prostate cancers.

As for the perception of cancer as a genetically inherited condition, it had to be stressed that "for the majority of us, there is susceptibility with no known genetic background".

The message had not got across to the public because the diet-cancer subject was relatively new - unlike awareness of the link between bad diet and heart disease - and because of the absence of direct evidence of the link - yet. Once there was evidence of genetic damage attributable to diet, attitudes would change, Dr Bingham predicted.

Dr Margaret Manson, a biochemist at the University of Leicester, outlined research confirming the potential of a variety of molecules found in vegetables, spices and tea, which helped prevent cancer. They acted as chemopreventive agents by impairing the signalling system associated with cancer cell production.

Both drugs and natural constituents in food could interact beneficially in disrupting the cancer signal. A molecule found in cabbage and related vegetables could be used to prevent breast cancer. Equally, curcumin, which is found in turmeric spice (which gives curries their rich colour), had characteristics similar to aspirin and was pertinent to colon cancer prevention.