Walnuts may soon become the next great health food following a study showing that they can boost the body's ability to withstand the effects of a fatty diet.

Scientists have shown that raw walnuts can increase the flexibility of arteries, making heart attacks and coronary disease less likely.

Walnuts contain natural chemicals that help to prevent the hardening of the arteries, making them less prone to becoming blocked, said Emilio Ros, of the Hospital Clinico in Barcelona.

"Each time we eat a high-fat meal, the fat molecules trigger an inflammatory reaction that , among other ill-effects, reduces the elasticity of the arteries," Dr Ros said. "Over time this repeated damage is thought to contribute to hardening of the arteries and, in turn, to heart disease. Our research shows that eating walnuts helps to maintain the elasticity of the arteries."

The research, funded by the California Walnut Commission and published in the Journal of the American College of Cardiology, involved 24 adults. Volunteers were divided into two groups who for two weeks followed a Mediterranean diet designed to lower cholesterol levels, which was rich in fruit and vegetables and low in dairy products. Each group was given a high-fat meal of a salami-and-cheese sandwich followed by a full-fat yoghurt. One was also given five teaspoons of olive oil and the other was given about eight shelled walnuts.

The scientists found that the walnuts and the olive oil helped to decrease the sudden onset of inflammation and oxidation in the arteries - processes that contribute to the hardening of arteries. However, the walnuts also helped to preserve the elasticity and flexibility of the arteries, regardless of cholesterol levels, which enabled the blood vessels to expand when needed to increase the flow of blood.

Dr Ros said that walnuts are rich in an amino acid called arginine, which is important in the production of the body's natural sources of nitric oxide, a substance needed to keep arteries flexible. Walnuts also contain antioxidants and alpha-linolenic acid, a plant-based omega-3 fatty acid, which some scientists believe can help to stave off heart disease.