According to Spanish researchers walnuts might be even better for the arteries than olive oil.
Researchers at the Lipid Clinic at Hospital Clinico in Barcelona say that following a fatty meal the arteries of the those who ate the walnuts stayed more flexible and elastic.
Ros and colleagues studied 24 nonsmoking, normal-weight adults, all with normal blood pressure and although half of the participants had elevated cholesterol they were not taking any medications for it.
Two weeks before and during the study, the volunteers went on a strict Mediterranean diet, low in fats and meats but high in fiber, fruits, and vegetables.
The volunteers then ate a salami-and-cheese sandwich on white bread with a small serving of full-fat yogurt; half the volunteers had walnuts (about eight nuts) added to this meal, while the other half had about 5 teaspoons of olive oil added to the meal.
After one week, the same high-fat meal was served and the volunteers who had previously had walnuts were switched to olive oil; those who had olive oil were switched to walnuts.
The Spanish researchers by using ultrasound examinations were able to see that both the olive oil and the walnuts decreased the onset of inflammation and oxidation in the arteries following a high-fat meal, but the walnuts preserved the blood vessels' flexibility while olive oil did not.
Lead researcher Dr. Emilio Ros, director of the clinic attributes the beneficial effect to the alpha-linolenic acid found in walnuts which is similar to the omega-3 fatty acids found in fish.
As Dr. Ros notes many experts, as well as the American Heart Association, recommend that Americans eat at least two fish servings of oily fish rich in omega-3 fatty acids a week, as that increases the good HDL cholesterol levels in the blood, which helps keep arteries clear.
But as Ros points out fish is not always available and is not as easy to buy and consume as walnuts.
The California Walnut Board funded this and several similar studies and petitioned the U.S. Food and Drug Administration over two years ago for permission to formally claim that walnuts reduce the risk of heart disease.
To date the FDA has only approved a "qualified health claim", which says that research 'supports' that eating 1.5 ounces of walnuts per day as part of a low-saturated-fat and low cholesterol diet, may reduce the risk of coronary heart disease."
The American College of Cardiology in it's review by Dr. Robert A. Vogel, professor of medicine at the University of Maryland, states that the protective fat from walnuts undoes some of the detrimental effects of a high-saturated-fat diet, whereas a neutral fat, such as olive oil, does not have as much protective ability.
Vogel says research indicates that those who eat the so-called "Mediterranean diet" in the belief that olive oil provides the major cardiac benefit, will see this is not true and other factors in the diet, including that it is a relatively rich source of nuts, are more likely, and olive oil is not the key protective factor in the Mediterranean diet.
Vogel also says more research is needed to determine whether the protective effect of walnuts is affected by heating and cooking, or whether they are best eaten raw.
Ros serves on the scientific advisory board of the California Walnut Commission, which partially funded the study and provided it with nuts.
The research is published in the upcoming issue of the Journal of the American College of Cardiology.