A high-fat dinner followed by an unusual dessert
suggests that walnuts might be even better for
the arteries than olive oil, Spanish researchers
The dinner consisted of a salami and cheese
sandwich on white bread, plus high-fat yogurt.
The "dessert" consisted of five teaspoons
of olive oil for half the diners and 40 grams
of walnuts (about eight shelled nuts) for the
Ultrasound examinations showed that the arteries
of those eating the walnuts stayed more flexible
and elastic after the fatty meal those of the
folks who ate olive oil. The study's 24 adult
participants had varying levels of blood cholesterol,
ranging from healthy to moderately high.
"This study shows the mechanism for the
beneficial effects of walnuts," contended
study lead researcher Dr. Emilio Ros, director
of the Lipid Clinic at Hospital Clinico in Barcelona.
Both olive oil and walnuts decrease the onset
of inflammation and oxidation in the arteries
after a high-fat meal, but walnuts preserve
the blood vessels' flexibility while olive oil
does not, according to Ros. He attributed much
of the beneficial effect to the alpha-linolenic
acid found in walnuts. This nutrient is similar
to the omega-3 fatty acids found in fish.
The study, which was funded in part by the
California Walnut Board, was expected to be
published in the Oct. 17 issue of the Journal
of the American College of Cardiology.
Ros points out that authorities such as the
American Heart Association
recommend that Americans eat at least two fish
servings a week, preferable oily fish rich in
omega-3 fatty acids. Omega-3s increase blood
levels of HDL cholesterol, the "good"
kind that helps keep arteries clear.
The only problem with that recommendation,
Ros said, is that fish isn't as easy to buy
and consume as walnuts. The alpha-linolenic
acid in walnuts has the same chemical structure
as omega-3 fatty acids, he noted, and "linolenic
acid found in plant foods provide an inexhaustible
supply, while fish are being depleted."
The California Walnut Board -- which has also
funded several similar studies -- petitioned
the U.S. Food and Drug
Administration more than two years ago
for its permission to formally claim that walnuts
reduce the risk of heart disease.
So far, the FDA has only approved a "qualified
health claim," which says that "supportive
but not conclusive research shows that eating
1.5 ounces of walnuts per day as part of a low-saturated-fat
and low cholesterol diet, and not resulting
in increased caloric intake, may reduce the
risk of coronary heart disease."
For its part, the American College of Cardiology
had the paper reviewed by Dr. Robert A. Vogel,
professor of medicine at the University of Maryland.
He issued a statement saying, "This demonstrates
that the protective fat from walnuts actually
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
People who eat the so-called "Mediterranean
diet" -- lauded by many nutritionists as
heart-healthy -- believe that olive oil provides
the major cardiac benefit, "but this research
indicates that's not true," Vogel said.
"There are probably other factors in the
diet, including that it is a relatively rich
source of nuts."
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, he added.