How much protection do certain types of food provide against various diseases? Read on...
Definitely protective. Hundreds of studies confirm a link. At least five portions a day are needed for optimum protection - deep green and orange/yellow varieties provide the highest amounts of the protective components such as carotenoids, flavonoids and vitamin C.
Definitely protective. Researchers have estimated that those eating plenty of fruit and vegetables can reduce the risk of heart disease by 15 per cent compared with those whose daily intake is low.
Against high blood pressure
Probably protective. The Dietary Approaches to Stop Hypertension (DASH) trial at Harvard Medical School in America, found that subjects with increased fruit and vegetable intake reduced their blood pressure. The effect was more marked with other health changes.
Possibly protective. Eating fruit and vegetables creates an alkaline environment within the body which may maintain the strength of bone, say researchers at the Human Nutrition Research Centre on Aging at Tufts University in Boston, America.
Possibly protective. Studies show that the percentage of people consuming five or more fruits and vegetables daily was higher among a group who remained diabetes-free, than among a similar group who developed the disease.
Possibly harmful. A handful of studies have suggested a link between milk consumption and prostate and kidney cancers. For colon and breast cancer there is some evidence that dairy products might be protective.
Possibly harmful. Full-fat milk supplies saturated fats which are linked with heart disease. Semi-skimmed provides much lower amounts, and skimmed virtually none.
Against high blood pressure
Possibly protects. The American DASH trial suggests that, as part of an overall healthy diet, low-fat dairy products play a role in reducing high blood pressure.
Probably protects. As a source of calcium, it's second to none. But it's not a panacea; nations that don't drink milk don't necessarily have higher osteoporosis rates.
Possibly harmful. Some babies who drink cow's milk too early (before six months) may be at risk of childonset diabetes. Proteins permeate their immature gut which may stimulate the formation of antibodies that destroy pancreatic tissue.
Probably harmful. Diets high in salt probably increase stomach cancer, according to a joint World Cancer Research Fund / American Institute for Cancer Research report. Rates are highest in Japan, China and Latin America where salted food is traditionally eaten.
Possibly harmful. Salt is harmful by implication only - because of it raises blood pressure.
Against high blood pressure
Definitely harmful. The American DASH trial showed that even on a healthy diet, blood pressure could be lowered further by also reducing salt intake.
Possibly harmful. Every 9g of salt (amount we eat daily) removes 60mg of calcium from the body via urine. The effect on osteoporosis is unclear.
Definitely harmful. Cancers increased by alcohol include mouth and oesophageal, breast and colon. Risk of oesophageal cancer increases 20-fold between drinking half a pint of beer a day and 20 pints.
Probably protective. Several reports indicate that moderate drinkers consuming 1-2 units a day have lower cholesterol levels. But only men over 40 and post-menopausal women reap tangible benefits.
Against high blood pressure
Definitely harmful. Alcohol constricts blood vessels, thus increasing blood pressure. Abstaining leads to a prompt fall in blood pressure in previously heavy drinkers.
Possibly protective. In post-menopausal women, moderate alcohol might reduce bone loss by increasing the circulating levels of oestrogen, say scientists at the Mayo Clinic in Rochester, Minnesota, USA.
Definitely protective. There's some evidence that oily fish may be associated with lower risk of cancers of the colon and rectum.
Definitely protective. The Government's Nutritional Aspects of Cardiovascular Disease report recommends eating at least one oily fish portion a week to protect against heart disease. Omega-3 oils help to prevent blood clots and improve blood flow.
Against high blood pressure
Probably protective. There's increasing evidence that the Omega-3 fats in oily fish might help to improve blood flow and lower blood pressure.
Possibly protective. Canned fish with bones (eg canned salmon or sardines) is high in vitamin D, which is an essential bone-strengthening nutrient.
Possibly protective. Oily fish may help to improve glucose control, according to some studies.
Processed Meats (Pies, Sausages, Burgers)
Possibly harmful. Vegetarians tend to have lower cancer rates due to a higher fruit and vegetable consumption rather than because of the absence of meat. Meat products that contain saturated fats increase colon cancer risk. Chargrilling meat also increases carcinogens.
Definitely harmful. As one of the biggest providers of saturated fats, processed meat products are known to increase cholesterol and the risk of heart disease.
Against high blood pressure
Probably harmful. Processed meats are generally high in salt, which contributes to high blood pressure.
Possibly harmful. May contribute to obesity, which is a major risk factor for diabetes.
Whole Grain Foods (Bread, pasta abnd cereals)
Possibly protective. High fibre whole grains speed up the rate at which food passes through the gut, which means that cancer-promoting toxins stay in contact with the gut wall for a shorter time.
Definitely protective. Between 1996 and 2001 an accumulation of five large studies in the USA, Finland and Norway all reported that subjects consuming relatively large amounts of whole grain cereals had significantly lower rates of coronary heart disease.
Against high blood pressure
Possibly protective. Results from America's DASH trial suggests they are helpful for lowering blood pressure as part of a wider healthy diet.
Possibly protective. A diet rich in unprocessed whole grains may help prevent or manage diabetes because it helps ensure blood glucose levels don't fluctuate too much.
Possibly harmful. Sugar might be associated with increased colorectal cancer risk. Risk appears to be double for someone consuming 60g of sugar a day compared with none.
Possibly harmful. Rapidly digested and absorbed carbohydrates with a high dietary glycaemic load (eg sugar) may increase risk of heart disease, especially in overweight women.
Against high blood pressure
Possibly harmful. Contrary to belief, sugar is not the main cause of diabetes - in fact scientists have failed to find any direct link. Diets high in refined carbohydrates overall may pose a risk, but obesity and a sedentary lifestyle are much bigger factors.
