Legumes play an important role in traditional diets in many parts of the world. They are low in fat, are good sources of protein and fiber, and contain a variety of micronutrients and phytoestrogens (plant estrogens). Phytoestrogens have received a lot of attention for their ability to fight not only cancer, but also heart disease and osteoporosis. They help balance hormones in the body and thus are thought to be particularly valuable for the hormone-dependent cancers: breast cancer and prostate cancer. It is well known that male hormones play a role in prostate cancer development.

Despite their advantages, legumes play a minor role in most Western diets. The typical Western based diet (lower in vegetables and legumes and higher in animal-based foods) can cause an increase in both male and female hormones (androgens and estrogens), while a plant-based diet tends to lower these hormones. This is the basis for the role of diet in the development of hormone-dependent cancers.

Soy foods, such as tofu, soy milk, soy beans, and vegetarian burgers, seem to be particularly rich in cancer-fighting properties. This is at least partially due to a form of phytoestrogen, called isoflavones, that is found primarily in soy. It appears to help prevent prostate cancer by binding to male hormone receptors in the prostate, thus reducing the stimulating effect of male hormones on prostate cell growth.

Epidemiological studies have shown that high levels of isoflavones are often associated with low rates of breast, colon, and prostate cancer. This has been used to explain why countries such as Japan and China that typically consume large amounts of soy have lower risks of these diseases.

The difficulty with consuming soy for reducing risk of prostate cancer is the lack of clinical trial evidence to support its use. As with any dietary component, it is difficult to isolate the effect of a particular food type to prove its effectiveness. One prospective study, including over 12,000 men, did evaluate consumption of soy milk. It found that those who drank soy milk regularly had a reduced risk of prostate cancer. The relationship held up after other factors were controlled for. Other studies need to be done to further establish the benefits of soy. In the meantime, getting more soy foods into your diet can be healthy for many reasons, and lowering your risk of prostate cancer may be one of these.

The foods we eat can affect our risk of developing certain types of cancer. High energy and high fat diets can lead to obesity and are generally thought to increase the risk of some cancers. Plant-based diets high in fresh fruits, vegetables, legumes and wholegrain foods may help to prevent cancer.

Diet is just one of the lifestyle factors that influence the risk of developing cancer. Smoking, obesity, alcohol, sun exposure and physical activity levels are also important. Although some foods can affect cancer risk, there is no evidence that specific foods can cause or cure cancer.

Food and some common cancers
Some common cancers (and how they are affected by what we eat) include:

• Lung cancer – this 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. It is thought that compounds called carotenoids (present in significant amounts in fruits and vegetables), as well as vitamin E, 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 and may, in fact, increase the risk of developing cancer in those who smoke. While fruits and vegetables may offer some degree of protection, not smoking in the first place is by far the best prevention.

• Breast cancer – this 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. Much of the risk of developing breast cancer involves factors that influence oestrogen levels during a woman’s reproductive life, such as age of menarche (first period), number of pregnancies and breastfeeding practices. Post menopausal women who are carrying too much weight, especially around their middle, have more than twice the average risk of breast cancer. Diets high in mono-unsaturated fat and high in vegetables and fruits may reduce the risk, while alcohol consumption increases the risk.

• Prostate cancer – a quarter of all new cancers diagnosed in men in UK is prostate cancer. Vegetables, soy in particular may decrease the risk, while a high fat diet that comprises mostly animal fat sources (such as dairy products, fatty meats and takeaway foods) may increase the risk. Lycopene is a potent antioxidant found in tomatoes, tomato-based products, watermelon and strawberries. It may also help lower the risk of prostate cancer.

• Bowel cancer – this is the fourth most common cancer in the world. Up to 70 per cent of cases can be prevented by following a healthy lifestyle. Keeping a healthy weight, being physically active and a diet high in vegetables and fibre are protective, while consuming a large amount of red meat (especially processed meat) and alcohol may increase the risk.

Foods to ‘eat less’
Foods to limit in your diet or eat less of include:

• Fatty processed red meats

• Highly processed foods that are low in fibre

• Heavily salted and pickled foods.

Foods to ‘eat more’
The strongest protective anti-cancer effect has been shown with:

• Vegetables, especially raw vegetables or salads

• Leafy green vegetables

• Carrots

• Tomatoes

• Citrus fruits

• Cruciferous vegetables like broccoli, cabbage, brussels sprouts, bok choy and other Asian greens.

Include more of these vegetables and fruits in your diet along with other varieties.

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 bowel cancer
There is now convincing scientific evidence that eating processed meat increases bowel cancer risk. The World Cancer Research Fund (WCRF) has recently recommended that people avoid eating processed meat. Processed meats are any meat that has been preserved by curing, salting or smoking, or by adding chemical preservatives. These meats include hot dogs, ham, bacon and some sausages and burgers.

It is recommended that children are not given processed meats at all. This is because many of the habits we develop as children last into adulthood. Substitutes for processed meats that are recommended for children include poultry or fish, low fat cheese or small amounts of lean meat.

The WCRF also recommends limiting the amount of fresh red meat we eat to 500g (cooked weight) a week. This is because there is convincing evidence that red meat also increases a person’s risk of bowel cancer.

Some research suggests that eating burnt or charred meat may increase cancer risk, but the evidence is unclear.

Fats and cancer
There has been a great deal of interest in the possible association between fat and cancer. Current evidence does not indicate a direct link between fat intake and particular types of cancer (with the possible exception of prostate cancer). However, a high fat diet may lead to obesity, which is a risk factor for several cancers including cancer of the colon, breast, kidney, oesophagus, gallbladder and endometrium.

Supplements are not the answer
Results of studies that 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 nutrient supplements at doses higher than the amount of that nutrient normally eaten in foods.

Suspect foods examined
While a high energy, low fibre diet may increase a person’s risk of developing cancer, some individual foods have also been singled out as potentially causing cancer (carcinogenic). These include:

• Artificial sweeteners – such as aspartame, saccharin and cyclamate. Laboratory rats can develop bladder cancer if fed huge amounts of saccharin or cyclamate, although this is at levels thousands of times greater than a normal diet. International studies agree that humans aren’t affected in the same way. Artificial sweeteners are considered safe to eat.

• Cured, pickled or salty foods – there is no conclusive evidence that red 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. Salt has also been associated with an increased risk of stomach cancer and should be consumed in limited amounts.

• Burnt or barbecued foods – a group of carcinogenic substances called polycyclic aromatic hydrocarbons (PAHs) can be produced if foods are overheated or burnt. Although charred or smoked foods could contain traces of PAHs, experts agree that the amount in the average UK diet is too low to be considered a significant cancer risk. However, when cooking, it’s best to use relatively low temperature methods wherever possible. These include steaming, boiling, poaching, stewing, casseroling, braising, baking, stir-frying, microwaving or roasting. Avoiding char-grilled meats and foods would also be smart.

• Peanuts – some laboratory animals can develop cancer after eating peanuts that are contaminated with toxin-producing moulds. However, peanuts sold in the UK are generally uncontaminated and contamination is routinely screened for.

• Alcohol – consuming alcohol increases the risk of cancers of the mouth, pharynx, larynx, oesophagus, breast and liver. The risk is even greater in those people who smoke. Alcohol has also been associated with colon, breast and rectal cancers. Men should drink less than two standard drinks a day and women less than one standard drink a day.

Treating cancer with food
While 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 micro nutrients 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.

• Extra protein may be needed to help prevent loss of muscle from weight loss.

Things to remember

• High fat, low fibre diets may 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.

Disability - fibre and constipation

Some people with disabilities suffer from constipation. Contributing factors can include the medications that they may take, low levels of physical activity, insufficient fluids and a diet that may be too low in fibre. Increasing the amount of fibre in the diet not only treats constipation but also lowers cholesterol, may reduce the risk of various cancers and bowel diseases, and improves general health and well-being

Two main types of fibre
The two broad categories of fibre include:

• Soluble fibre - softens the faeces by absorbing water and helps slow the rate of digestion and lower blood cholesterol and blood glucose. It is found in a range of foods including legumes, fruits, vegetables and oat bran

• Insoluble fibre - helps prevent constipation and other associated disorders, such as haemorrhoids, by adding bulk to the faeces and making the food products pass more quickly through the bowel. It is found in a range of foods including wheat bran and wholegrain cereals and breads.

Fibre keeps the digestive system healthy
Fibre:

• Encourages the passage of food and wastes through the digestive system (peristalsis).

• Reduces the risk of bowel diseases such as chronic constipation, diverticulitis and irritable bowel syndrome.

• May reduce the risk of various cancers, particularly those of the bowel.

Fluid is also important
Fibre can only help to relieve constipation if there is enough fluid in the diet for it to be able to do its work. Fibre absorbs water to produce a soft and bulky stool. Everyone should drink at least 2 litres of water each day, particularly in hot weather. Some people with a disability may need to be reminded to drink regularly. Water is the best drink.

Inactivity can cause constipation
Some people with a disability have conditions that affect their mobility, and this can also be a reason why a person is constipated. A person with a disability needs to be as active as possible each day, as every little bit of regular exercise helps.

Fibre can help with other health problems
A diet rich in fibre can help in many ways, including:

• Weight management - obesity increases the risk of a range of health problems, including diabetes and heart disease. Fibre is key to healthy weight management. Since it is indigestible, it provides a sensation of fullness without the kilojoules.

• Atherosclerosis - high blood cholesterol is a contributing factor in the development of atherosclerosis (narrowing of the arteries), which can cause a range of health problems including high blood pressure and heart disease. Soluble fibre (such as legumes, fruits and vegetables) helps to reduce blood cholesterol.

• Diabetes - a diet high in soluble fibre is digested and absorbed more slowly, which leads to lower blood glucose levels.

How much fibre?
Dietitians generally recommend about 30g of fibre every day. Packaged foods such as breads and cereals include nutrition information labels, which can help you to calculate your fibre intake, and nutrition books often include fibre charts. A dietitian can provide information to individuals on the type and quantities of foods that need to be eaten to achieve 30g of daily fibre in the diet each day. Examples of the fibre content in some foods include:

• Four slices of wholemeal bread - about 7g

• Half a cup of baked beans - about 7g

• Two medium pieces of fruit - about 6g.

General cautions
Changes to eating habits should be made with some care. For example:

• A sudden increase in dietary fibre can upset the digestive system and cause symptoms including flatulence (gas) and abdominal pain. It is better to slowly increase the amount of fibre in the diet over a period of several weeks.

• Diets that are too high in fibre can hinder the absorption of certain minerals including iron, zinc and calcium. Avoid consuming more than 35g of fibre per day.

• Do not use fibre supplements unless you have checked with your doctor or dietitian, since these products can aggravate or cause constipation, particularly if you don’t drink enough fluids. Some people with a disability have swallowing problems. Many fibre supplements thicken when added to fluid and this may cause a person with swallowing problems to choke.

• It is important to drink sufficient fluids. It may be helpful to always include a glass of water at each meal or snack.

Things to remember

• Some people with a disability suffer from constipation.

• Contributing factors can include medications, low levels of physical activity, insufficient fluids and a diet that is low in fibre.

• Dietitians generally recommend about 30g of fibre every day.