Cancer & Food

Current research indicates that the foods we eat can influence our susceptibility to certain types of cancer. Generally, high fat diets are thought to increase the risk, while plant based diets - high in fresh fruits, vegetables, legumes and wholegrains, and minimally processed starchy foods - can help to prevent cancer. Diet is just one of the lifestyle factors that influence the risk of developing cancer. Smoking, obesity and physical activity levels are also important determinants of cancer susceptibility.

Food and some common cancer

Some common cancers and how they are affected by what we eat:

Lung cancer is the leading cause of death from cancer in the world and smoking is mostly responsible. There is convincing evidence that diets high in vegetables and fruits are protective against lung cancer and that compounds called carotenoids, which are present in significant amounts in these foods, are probably responsible for some of this effect. However, the use of antioxidant supplements, such as beta-carotene and vitamin E, has not been proven to be effective in either prevention or treatment of lung cancer.
Breast cancer is the most common type of cancer in women in the world. There is an increased risk of breast cancer with factors such as rapid early growth, greater adult height and weight gain in adulthood. Diets high in mono-unsaturated fat may reduce the risk, while alcohol consumption increases the risk.
Prostate cancer is the third most common cause of death of men in Australia. Vegetables - soy in particular - may decrease the risk, while animal fat, red meat and dairy products may increase the risk.
Bowel cancer is the fourth most common cancer in the world. Up to 70 per cent of cases can be prevented by following a healthy lifestyle. Physical activity and vegetable intake are protective, while a high red meat intake and alcohol probably increase the risk.

How eating carefully can reduce the risk of cancer

Less desirable foods
The typical cancer promoting diet seems to be:
· High in fat, especially animal fat
· Low fibre
· High in processed starchy foods
· Low in fresh vegetables
· Low in fruits
· Low in whole grains.

More desirable foods
The strongest protective anti-cancer effect has been shown with:
· Vegetables, especially raw vegetables or salads
· Leafy green vegetables
· Onions and garlic
· Carrots
· Tomatoes
· Citrus fruits
· Cruciferous vegetables - such as broccoli, cabbage, brussel sprouts, bok choy and other Asian greens.

These vegetables and fruits should not be eaten to the exclusion of other varieties. Eating a variety of all fruits and vegetables will provide the greatest number of protective factors, some of which are yet to be discovered.

Seven a day
Eating seven or more serves daily of a variety of grains, grain products, legumes, roots and tubers will also provide protective benefits against cancer. The less processed the grains, the better; diets high in refined starch and refined sugar may increase the risk of stomach cancer and bowel cancer.

Meat and cancer
There is no evidence that meat causes cancer. However, diets high in red meat (beef, pork and lamb) may increase the risk of the bowel cancer and possibly cancers of the breast, pancreas, prostate and kidney. When red meat is eaten, it should be limited to less than 80g per day. It is preferable to choose fish, poultry, or meat from non-domesticated animals in place of red meat.

While the fat, protein and iron content of meat - as well as the method used to cook it - have all been considered as possible explanations, it is not exactly known why a high meat diet is linked with an increased risk of cancer. It may be that meat itself does not cause cancer, but that meat rich diets simply don't provide as much protection against cancer as plant foods.

Fats and cancer
Fatty foods, particularly those containing animal fats, should be limited in the diet. Vegetable oils should be used instead of animal fats wherever possible and in moderation. Mono-unsaturated vegetable oils, such as olive and canola oil, seem to provide the most protective benefits against cancer. Plant oils are preferable in their natural liquid form to solid forms such as margarine.

Results of studies which show a protective effect of foods containing certain nutrients should not be taken to mean that these nutrients, when isolated and taken as supplements, will provide the same benefits for cancer prevention. In some cases, there has been an increased risk of cancer in those people who take supplements.

Suspect foods examined
While a high fat, low fibre diet increases a person's risk of developing cancer, some individual foods have been singled out as potentially carcinogenic. These include:
Artificial sweeteners - such as saccharin and cyclamate. Laboratory rats can develop bladder cancer if fed huge amounts of saccharin, but international studies agree that humans aren't affected in the same way. Artificial sweeteners are considered safe to eat.
Cured, pickled or salty meats - there is no conclusive evidence that meat causes cancer. However, bacon and other cured or pickled meats contain a substance called nitrate, which has the potential to cause cancer in laboratory animals when eaten in huge doses. How this research relates to humans isn't clear. To be on the safe side, it is best to limit the amount of cured meats in the diet because they are generally high in fat and salt. Furthermore, salt has been associated with an increased risk of stomach cancer and should therefore been consumed in limited amounts.
Burnt or barbecued foods - a group of carcinogenic substances called polycyclic aromatic hydrocarbons (PAHs) can be produced if foods or wood are overheated or burnt. Although charred or smoked foods could contain traces of PAHs, experts agree that the amount in the average Australian diet is too low to be considered a significant cancer risk. However, when cooking it's best - wherever possible- to use relatively low temperature methods such as steaming, boiling, poaching, stewing, casseroling, braising, baking, stir frying, microwaving or roasting.
Peanuts - some laboratory animals can develop cancer after eating peanuts that are contaminated with toxin-producing moulds. However, peanuts in Australia are generally uncontaminated.
Alcohol - increases the risk of cancers of the mouth, pharynx, larynx, oesophagus and liver, with the risk even greater in those people who smoke. Alcohol has also been associated with causing colon, breast and rectal cancers. Men should drink less than two standard drinks per day and women less than one standard drink per day.

Treating cancer with food
While we know that food plays an important role in preventing some cancers, the therapeutic value of food in treating existing cancer is less clear. It is true that a person with cancer needs excellent nutrition in order to better cope with the physical demands of the illness and the rigours of medical treatment. However, claims that particular foods, vitamins or micronutrients can kill cancer cells should be viewed with scepticism. To date, there is little scientific proof that a particular food or supplement can cure cancer or destroy cancer cells.

Recently some Japanese studies have found that green tea may delay the development and spread of certain cancers. Other studies have suggested that soy may also have a similar effect. Although this work is preliminary, it may suggest a more important role for food in the treatment of cancer in the future.

Nutrition for the person with cancer is important for many reasons, including:
· The immune system needs bolstering to fight at full strength.
· The diet may be adjusted to cope with various symptoms, such as constipation, diarrhoea or nausea.
· Loss of appetite or an increased metabolism means that high energy foods may need to be included in the daily diet.


Things to remember
High fat, low fibre diets can increase the risk of many cancers, including, bowel, lung, prostate and uterine cancers.
You can reduce your risk of developing cancer by eating more fresh fruits, leafy green vegetables and wholegrain foods.
Even though diet can influence your risk of developing cancer, there is little evidence that special foods can be used to cure existing cancers.

Article co-authored by Better Health Channel
(Australian -Victorian Government website)

Last Updated: August 2003