People must remember that they are high in fat and that can lead to increasing calorie levels

Collette Kelly, from the British Nutrition Foundation

Reducing cholesterol

A study in the American Journal for Clinical Nutrition found walnuts appear to change the way the body breaks down fats, which has the effect of reducing of the potential harmful cholesterol even though it doesn't reduce the overall levels of fat in the blood.

The walnuts were unique as rich sources for n-6 and particularly n-3 polyunsaturated fatty acids.

N-3 polyunsaturated fatty acids have beneficial effects on blood clotting and regulating the heart beat

The researchers found that when they added walnuts to the diet of both men and women that it was successful in reducing their cholesterol levels.

The five test men and 13 postmenopausal women, who were an average of 60 years old, all had high serum cholesterol levels.

Over a five to 12 month period they ate four diets in sequence.

First they had their habitual diet; then their habitual diet with walnuts; then a low fat diet and finally a low fat diet with walnuts.

The walnuts were provided at 48 grams per 1,850 dietary calories a day.

Scientists found that compared with both their normal diet and a low fat diet those who ate the walnuts had much lower cholesterol levels.

Calorie care

The scientists found the walnuts had a particular effect on low-density lipoprotein (LDL), which has been linked to cardiovascular disease.

They found that when eaten with the normal diet LDL levels dropped by 27% and 7% with a low fat diet.

Although nuts are high in calories none of those who went on the diet gained any weight, although they did find that their energy levels had increased.

Colette Kelly, a nutrition scientist from the British Nutrition Foundation, stressed that anyone following the diet should take care over their fat intakes.

She said walnuts are high in fats and that people should try to replace saturated fats, such as butter, cakes and pastries, with the nuts.

"People must remember that they are high in fat and that can lead to increasing calorie levels.

"It is probably a matter of substituting walnuts for saturated fats."