If you are trying to slim down, you may have crossed cheese off the menu.

But scientists have discovered it may actually help prevent diabetes an illness often triggered by being overweight.

They claim that eating just two slices of cheese a day cuts the risk of type 2 diabetes by 12 per cent.

The findings go against current health guidelines, which advise cutting back on dairy products and other high-fat foods to help prevent the illness.

Around 2.5million Britons have diabetes. Of these, 90 per cent suffer from type 2, which is often caused by being very overweight.

But experts fear another million have the condition, which can cause heart attacks, strokes, blindness and nerve problems, without yet having been diagnosed.

British and Dutch researchers looked at the diets of 16,800 healthy adults and 12,400 patients with type 2 diabetes from eight European countries, including the UK.

The study, published in the American Journal of Clinical Nutrition, found that those who ate at least 55g of cheese a day around two slices were 12 per cent less likely to develop type 2 diabetes. The risk fell by the same amount for those who ate 55g of yoghurt a day.

For years NHS guidelines have advised against eating too much dairy, cake or red meat as they are high in saturated fat. This is thought to increase cholesterol and raise the risk of diabetes.

But the researchers including academics from the Medical Research Council, Cambridge say not all saturated fats are as harmful as others, and some may even be beneficial.

One theory is that the so-called 'probiotic' bacteria in cheese and yoghurt lower cholesterol and produce certain vitamins which prevent diabetes.

And cheese, milk and yoghurt are also high in vitamin D, calcium and magnesium, which may help protect against the condition.

Diabetes occurs when the body does not produce enough of the hormone insulin to control its blood sugar levels. Symptoms of type 2 diabetes include feeling very thirsty, needing to pass water frequently and constant tiredness.

Although the illness is treatable through methods such as dietary changes, tablets and injections, it can cause serious complications if not properly looked after.

But despite the latest findings, campaigners warned against gorging on cheese and other dairy products in the hope of warding off diabetes.

Dr Iain Frame, director of research at the charity Diabetes UK, said: 'It is too simplistic to concentrate on individual foods.

'We recommend a healthy balanced diet, rich in fruit and vegetables and low in salt and fat.

'This study gives us no reason to believe that people should change their dairy intake in an attempt to avoid the condition.'