Diabetes mellitus affects around 2 per cent of the population and its incidence is becoming more common with 60,000 cases currently diagnosed each year.

What triggers the condition is not fully understood. It does seem clear, however, that like many ailments, its increased prevalence is linked to the Western lifestyle.

A 12 year study published in the British Medical Journal (H. Bodansky et al, 18 April 1992) shows that environment is a major factor. The researchers found that when children of families from an area where diabetes is rare move to an area where it is more common, they show a corresponding rise in the disease. The incidence of diabetes in Asian children in Bradford went from 3.1/100,000 per year in 1978-1981 to 11.7/100,000 per year in 1988-1990. The level for indigenous children remained constant at 10.5/100,000 per year.

Prescribed drugs and diet are thought to have a role as a trigger. A study looking at nutrients and food additives suggests a diet with large amounts of foods rich in protein and carbohydrate, along with food additives such as nitrosamines, may increase the likelihood of developing diabetes (Dr Gisela Dahlquist et al, BMJ, 19 May 1990). Other research suggests long term use of antihypertensive drugs thiazides, betablockers, hydralazine increases the odds of diabetes by a factor of around 1.7, independent of any other risk factors (Dr Elinar Skarfors et al, BMJ, 28 September 1991). Stress is also thought to play a part.

Diabetes is divided into two types: insulin dependent and non insulin dependent. With the first, which strikes younger people, the pancreas stops producing any insulin. (Insulin enables the body to convert sugar into energy; without it, sugar remains in the blood.) Treatment is by daily injections of insulin and by following a careful diet to match the amount of energy taken in with the amount of insulin injected so that blood sugar levels stay as near normal as possible.

The second type is also known as middle age onset diabetes. With this type, the pancreas stops producing sufficient insulin to counteract the amount of sugar in the blood. It is often treated by diet alone, or by diet and insulin stimulating drugs which have their own side effects (see below). Both types of diabetes can be associated with a range of side effects, commonly hypoglycaemia, where the blood sugar falls too low, causing the diabetic to pass out if not caught in time. In the longer term, raised blood sugar levels can lead to blindness, heart disease, kidney damage and gangrene.

Obesity is thought to be a major factor in triggering type two diabetes; however, a study published in The Lancet (28 September 1991) suggests regular exercise may help stave off diabetes, even in those who are overweight. The researchers tracked 87,253 American women between the ages of 34 and 59 for an eight year period. "Physical activity was associated with a greater reduction in risk of NIDDM (non insulin dependent diabetes mellitus) during this period for women exercising at least once a week compared with sedentary women," they said.

Leading nutritional doctor Stephen Davies believes low levels of chromium which tends to decrease with age may be a trigger of type two diabetes. "We have many examples of patients whose glycosolated haemoglobin [the part of the blood tested to measure blood sugar levels] has come down into the normal range once their chromium levels are raised," he says. Supplements of chromium and "judicious dietary intervention" may enable many more diabetics to control their condition without resorting to drugs. Recognized side effects of insulin stimulating drugs are nausea, anorexia, diarrhoea, skin allergies, reversible leucopaenia (reduction in the number of white corpuscles in the blood), thrombocytopenia (blood platelets reduction) and transient changes in liver enzymes. Davies recommends that elderly diabetics boost their chromium intake with 20-30 brewer's yeast tablets a day.