Walnuts Protect Arteries From Fat
Nuts May Be Key to Heart-Healthy Mediterranean Diet
Oct. 9, 2006 -- A handful of walnuts protects your arteries from the shock
of a high-fat meal, Spanish researchers find.
The finding suggests that nuts are a more important part of the
heart-healthy Mediterranean diet than olive oil. The Mediterranean diet is low
in saturated fats but high in monosaturated fats, particularly olive oil.
Heart health depends on healthy, flexible arteries. When you eat a high-fat
meal, it temporarily stuns your arteries. They stiffen and become less able to
expand in response to exercise. Over time, this repeated damage contributes to
hardening of the arteries.
But if you eat walnuts along with a fatty meal, the fat has much less of a
short-term effect, find Emilio Ros, MD, PhD, and colleagues. Ros is director of
the Lipid Clinic at Hospital Clínico, Barcelona, Spain, the central location
for the study.
"People would get the wrong message if they think that they can continue
eating unhealthy fats provided they add walnuts to their meals," Ros says
in a news release. "Instead, they should consider making walnuts part of a
healthy diet that limits saturated fats."
Ros serves on the scientific advisory board of the California Walnut
Commission, which partially funded the study and provided it with nuts.
Walnuts: The Anti-Salami?
Ros and colleagues studied 24 nonsmoking, normal-weight adults. They all had
normal blood pressure. Half of the participants had elevated cholesterol but
were not taking any medications for it. Two weeks before and during the study,
these 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.
Sophisticated tests showed that the high-fat meal had less of a blood-vessel
effect on those who ate the walnuts than on those who ate the olive oil.
Ros notes that walnuts contain a fatty acid called alpha-linolenic acid.
This plant-based fatty acid is similar to omega-3 fatty acid found in fish.
University of Maryland researcher Robert A. Vogel, MD, who did not
participate in the study, said the results show that the right foods -- in the
right combination -- can protect one's health.
"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 ability," Vogel
says in a news release. "This raises a very interesting issue because many
people who eat a Mediterranean diet believe the olive oil is providing the
benefits. But this research and other data indicate that's not true. There are
probably other factors in the diet, including that it is a relatively rich
source of nuts. This is not to say that olive oil is bad, but it’s not the key
protective factor in the Mediterranean diet."
Ros and colleagues report their findings in the Oct. 17 issue of the
Journal of the American College of Cardiology.