The role of food in the prevention of cancer needs to be distinguished from its role in the treatment and possible cure of cancer.

Certain cancers may be prevented by particular eating patterns. Cancers associated with diet include large bowel cancers, lung cancer, breast cancer in women, prostatic cancer in men, and cancer of the uterine cervix in women. Little is understood about the apparent increase in incidence of pancreatic cancer, but it seems likely that nutritional factors are involved.

The general approach to reduce risk of cancer is to:

  • increase intake of plant food, especially wholegrain cereal and fruits and vegetables of various kinds, so that at least 50 per cent of energy or calorie intake comes from these foods;
  • decrease intake of fat (probably to around 20 to 25 per cent of total energy or calorie intake), especially saturated animal fat, since this is usually the major fat in the western diet;
  • avoid obesity, especially by increasing levels of physical activity;
  • avoid other than occasional salted, cured or smoked foods,
  • be modest about alcohol intake, probably not more than an average of one standard drink (such as a glass of regular beer, a glass of wine, a nip of whisky, a glass of sherry) a day for women and two for men.

There is clear evidence that other lifestyle and environmental factors interact with food intake to affect the risk of cancer.

Examples include:

  • the protection of green leafy and yellow vegetables against bronchagenic (lung) cancer for a given level of cigarette smoking;
  • the increased risk of upper gastrointestinal and respiratory tract cancers where smoking and excess alcohol intake are combined;
  • the ability of increased physical activity to allow greater consumption of protective foods' such as plant foods. If you exercise more you can afford to eat more.

Be cautious about claims for cure or control of cancer with mega (large) doses of nutrients. It is rare to find that nutrients have useful pharmacological (medicinal) properties at doses higher than the amounts obtainable from food. Because of potential hazards, any therapy with high doses of nutrients must be carefully considered and then only undertaken under medical supervision.