Walnoten voor een gezond hart en goede bloedvaten.*
Uit een klein Spaans onderzoek blijkt dat walnoten misschien nog wel beter zijn dan olijfolie in de bestrijding van hart- en vaatziektes. In walnoten zit relatief veel van het omega-3 vetzuur ALA. Uit al eerdere onderzoeken is gebleken dat walnoten goed zijn om het goede cholesterol (HDL) te verhogen en aders soepel te houden. Bij dit onderzoek kregen deelnemers na afloop van een “vette” maaltijd of olijfolie of 8 walnoten als dessert. Zowel olijfolie als de walnoten bestreden de oxidatieschade ontstaan door het vette eten doch na het walnotendessert bleven de aders ook nog eens soepel zo bleek bij ultrasound onderzoek.
Walnuts
May Beat Olive Oil for Heart Health
--
A high-fat dinner followed by an unusual dessert suggests that walnuts might be
even better for the arteries than olive oil, Spanish researchers report.
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 other half.
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 ability."
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.
More
information
More on the nutritional benefits of walnuts
is found on the FDAs Web site (www.cfsan.fda.gov ).
(Okt. 2006)