Millions of pounds are spent every year on trying to find a cure for cancer. But research is discovering that certain fruit and vegetables contain substances which help protect against the disease. - by dietician Jane Brophy
People fear cancer more than any other disease - not surprisingly, when 440 people die from it every day in Britain. In fact, with a quarter of all deaths in the UK due to cancer, it's the second biggest killer after heart disease.
Yet if you do get cancer the chances of being cured are much higher than most people think, especially if the illness is detected early. And while millions of pounds are spent every year on trying to find the cure for cancer, many scientists believe that more could be done to prevent these premature deaths by one simple step - a change in diet.
Many scientific studies of vegetarians show that they are less likely to suffer from cancer than non-vegetarians. Cancer mortality rates for vegetarians are only 50-70 per cent of that expected; in other words vegetarians suffer half to a third less cancer. At first researchers thought that this was simply due to vegetarians smoking and drinking less than meat eaters as part of their general healthy lifestyle. But while that accounted for the lower rates of lung cancer and other tobacco and alcohol-related cancers, it didn't explain why mortality rates amongst vegetarians are still 40 per cent lower for some cancers, particularly of the bowel, which are unrelated to smoking and drinking.
Recent research has found that the answer lies in special protective substances found only in vegetable foods. One study of German vegetarians has shown that the lower cancer risk is partly related to a more active response of the immune system, which is thought to have been stimulated by substances in vegetarian foods.
Although the exact causes of cancer are not known for certain, the substances that can lead to its development are surprisingly well-defined. In a vegetarian diet the cancer-protecting aspects are related to not only what is left out - the meat - but also to what is included plentifully - cereals, pulses, nuts, seeds, fresh fruit and vegetables.
So what makes meat eating so dangerous in relation to developing cancer? Apart from the fact that meat is high in fat and contains no beneficial carbohydrate, dietary fibre or protective nutrients, it can also contain substances known to be carcinogenic or cancer-causing. Salt-cured and pickled meats, in particular, contain nitrates and nitrites that have been linked to cancer, particularly of the mouth, oesophagus and stomach, while smoked and charred foods contain numerous cancer-promoting chemicals similar to those found in tobacco smoke.
Fresh fruit and vegetables, on the other hand, contain substances which have been found actively to protect against cancer. According to Dr Timothy Key, a research scientist from the Cancer Epidemiology Unit at the University of Oxford, "The importance of diet is most certain for cancer of the large intestine, the commonest cancer in Britain after lung cancer. More research is urgently needed to find out exactly which dietary factors affect the chances of developing cancer of the large intestine, but studies so far suggest that animal fat and/or meat may increase the risk, while cereals fruit and vegetables may be protective. Fresh fruit and vegetables also appear to protect against other diseases including cancers of the oesophagus and stomach."
The World Health Organisation recommends that we double our intake of fruit and vegetables to at least 1lb a day, and that we include some nuts, seeds and pulses in our diet each day. The American Cancer Institute has just launched a campaign called "5 A Day" to persuade people to eat five servings of fruits and vegetables each day. From leading authorities on health matters, then, comes recognition that a vegetarian diet has an important part to play in preventing cancer.
Many medical studies are also now highlighting possible links between eating meat and developing cancer. The dietary factor most linked to bowel cancer - which kills 19,500 people a year in Britain - is eating meat.
Diets high in fat - such as a typical meat-based diet - increase the excretion of bile acids in the bowel which are thought to promote cancer. According to a recent American study of 89,000 women - the largest long-term study on diet and cancer - eating red meat every day means you are two and a half times as likely to develop colon cancer than if you ate it less than once a month. In a recent Swedish study when the diet of a group of volunteers was changed from meat-based to vegetarian a 75 per cent drop in one of the bowel acids associated with cancer was observed.
Yet although it is clear that diet can protect or promote cancer, scientists disagree about its exact contribution. Leading cancer specialist Sir Richard Doll estimates that diet is responsible for about 30-70 per cent of all cancers; according to the World Cancer Research Fund, the figure is between 35-60 per cent. But generally most cancer experts accept that at least a third of all cancers could be prevented by changes in diet.
The reason for the differences in opinion among the experts is that although diet is recognised as one of the most important causes of cancer, more research is needed to show which aspects of diet actually cause the disease. It is sometimes difficult to tease out the exact dietary factors that are responsible for a reduced cancer risk. A person who eats less meat often automatically eats more fruit, vegetable and fibre. Researchers have to work out whether it is the lack of meat or the inclusion of other protective substances or both which lowers the cancer risk in vegetarians.
But while the details of the relationships between cancer and foods may not yet be understood, and the mechanisms at work by the certain foods that protect against cancer are in many cases still a mystery, there is no doubt that some foods can promote cancer while others can protect against it.
The dietary factors which have been shown to promote cancer include a high fat diet, a diet high in meat, being overweight and eating too many pickled and smoked foods. A diet high in fat, particularly animal fat, can increase the risk of certain cancers such as breast, ovary, colon and prostate. Being overweight can increase the risk of colon, breast, gall bladder and endometrium (the womb lining) cancer. Since vegetarians tend to be closer to their ideal weight, eat less fat and avoid animal fats they considerably reduce their risk of suffering from a large number of cancers.
Amongst all the medical uncertainty about the causes and cures for cancer, one tact is reassuringly clear: we can all have some measure of control over whether or not we develop certain forms of cancer - just by going vegetarian.
What is Cancer?
Cancer occurs 'when living cells go wild'. Cancer cells are basically like any other cell in our body except that the DNA which stores all our genetic inheritance is distorted or lacking essential information. As a result cells go on dividing and growing without any regulation or restraint and compete with the body's normal cells. The cancer cells go on to invade other parts of the body and continue to grow and cause destruction.
Not all cancers are the same; each type represents a distinct disease. Most cancer experts agree that cancer is largely determined by environmental factors, such as radiation, asbestos and cancer-causing chemicals, or aspects of behaviour such as diet, drinking and smoking. A recent overview of all the evidence linking diet and cancer estimated that if environmental and dietary factors were removed, cancer in middle and old age could be reduced by 80-90 per cent.
Cut the Fat to Reduce Cancer Risk
Experts agree that cutting down on fat - both saturated and unsaturated - is one way of reducing the risk of cancer. The Department of Health recommends we make fat only 35 per cent of our energy intake, but other scientific evidence suggests that fat intake should account for only 20 per cent. Most fat comes from animal foods, like meat and dairy products, and so vegetarians tend naturally to have a diet lower in fat. To reduce your risk of cancer yet further, reduce your consumption of high fat dairy produce, minimise your intake of butter or margarine, avoid pastry and other high fat foods and if possible use no more than one tablespoon of high quality vegetable oil a day, perhaps in a salad dressing.
Soya and Cancer Protection
It has long been thought that the low rates of breast and colon cancer in Japan and China may be related to the high consumption of soya products. Soya beans contain high concentrations of substances now known to be cancer-preventers. Several studies show that soya consumption can reduce both colon and rectal cancer.
Thus to help lower you chances of getting cancer you should eat some of the many soya products on the market each day. Try tofu or tofu burgers, soya milk and tempeh.
Fibre and Cancer
Fibre gained world attention as an aid to preventing cancer when in 1971 a report was published showing that in countries where people consume high fibre diets they suffer considerably less bowel and rectal cancer.
Fibre in the diet decreases the time between eating and the elimination of waste material from the body so it reduces the contact time between cancer-causing chemicals and the intestine.
Vegetarians, who eat plenty of wholegrain cereals, pulses, fruit and vegetables, easily reach recommended amounts of fibre in their diet and suffer considerably less bowel cancer.
Free Radicals and Anti-Oxidants - the ACE Way to Health
Free radicals caught the media's attention in the late 1980s. You couldn't pick up a magazine or newspaper without finding an article about these highly reactive chemical particles thought to be behind a number of diseases including cancer.
But what exactly are they and how can we prevent them affecting our bodies? In fact free radicals occur normally and are an essential part of our body's metabolism. They form as a result of oxidation in the body, rather like an apple going brown or an oil going rancid. Alcohol consumption, being under emotional stress, air pollutants - particularly low-level ozone - pesticides, drugs, toxic metals like lead, cadmium and aluminium - can all increase the production of free radicals.
Left unchecked, a chain reaction occurs which multiplies the number of free radicals. We remain healthy as long as these reactions do not surge out of control, but if the concentration exceeds safe levels, the result is cell destruction, malignant mutation, tumour growth, damage to enzymes and inflammations. But there is natural protection against these destructive forces in the shape of anti-oxidant nutrients, the most important being the ACE vitamins - vitamins A, C and E and the mineral selenium. People who smoke or who are exposed to a very polluted environment require more anti-oxidant nutrients in their diet.
Sources of anti-oxidant nutrients that combat free radicals, and which are widely found in a typical vegetarian diet include:
Beta-carotene - dark green, yellow, orange and red vegetables such as carrots, tomatoes, spinach, peppers, watercress, broccoli, cherries, peaches, water melon and apricots.
Vitamin C - all fresh fruit and vegetables, particularly citrus fruits, strawberries, melon, blackcurrants, potatoes, green leafy vegetables and tomatoes.
Vitamin E - all wholegrain cereals including brown rice, oats and wholemeal bread, wheat germ, soya beans, cold-pressed vegetable oils, nuts, seeds, parsley, broccoli and asparagus.
Selenium - wholegrain cereals particularly in the wheat germ and bran, also onions, garlic and mushrooms.
