The small study, conducted at the Lipid Clinic in Barcelona, Spain substituted walnuts for about one-third of the calories from olives, olive oil, and other monounsaturated fats in a Mediterranean diet.
Twenty-one men and women with high cholesterol followed the walnut-enhanced Mediterranean diet, or a regular low-calorie Mediterranean diet, for four weeks.
Walnuts were found to increase the elasticity of arteries by 64 per cent, and to reduce cell adhesion molecules associated with hardening of the arteries by 20 per cent.
"This is the first time a whole food, not its isolated components, has shown this beneficial effect on vascular health," said lead author of the study, Emilio Ros, at the Hospital Clinic of Barcelona, who led the study.
The study was sponsored in part by the California Walnut Commission and full findings are published in the 23 March edition of Circulation.
Walnuts, one of the oldest food ingredients known to mankind, are a rich plant source of alpha-linolenic acid, a key essential fatty acid from which omega-3 fatty acids are derived.
In the US, the Food and Drug Administration (FDA) has cleared the health claim that 'eating 1.5 ounces per day of walnuts as part of a diet low in saturated fat and cholesterol may reduce the risk of heart disease'.
Key global producers of walnuts are the UK, China, Turkey, India, France, Kashmir, Italy and Chile. In the US the California walnut is the number one ingredient nut, representing over half of supermarket sales of shelled cooking nuts, said the US walnut commission quoting statistics from IRI infoscan.
This heart healthy ingredient is the focus of an upcoming EU-funded conference in Naples, Italy this November.