An analysis of studies has produced what its authors describe as a precise description of the beneficial effects of nut consumption on cholesterol and other heart-related fats.
It provides "the best evidence yet that eating nuts reduces LDL cholesterol and improves the blood lipids profile," said Dr Joan Sabate, who chairs the nutrition department at the Loma Linda University School of Public Health in California, and was a co-author of the report, published in Archives of Internal Medicine.
Sabate and fellow researchers at the university pooled data on 583 men and women who had participated in 25 nut consumption trials. The results showed that eating about 2.3 ounces of nuts a day -- a third of a cupful -- reduced total cholesterol levels by 5.1% and "bad" LDL cholesterol by 7.4%.
That amount of nut eating also improved the ratio of LDL cholesterol to "good" HDL cholesterol by 8.3 percent and caused a decrease of 10.2% in triglyceride levels among people with high levels of those blood fats.
Sabate is a leading figure in the somewhat limited field of nut nutrition. His first report on the beneficial effects, published in 1993, led to other studies that eventually prompted the US Food and Drug Administration to issue a qualified health claim for nuts a decade later.
The 2003 FDA statement said that "scientific evidence suggests, but does not prove, that eating 1.5 ounces of most nuts per day, as part of a diet low in saturated fat and cholesterol, may reduce the risk of heart disease."
On food labels, that claim is followed by a caution: "See nutrition information for fat content."
The FDA statement was issued in response to a petition filed by the International Tree Nut Council Research and Education Foundation, which supports the work done by Sabate and other nut nutrition researchers. The foundation helped fund the latest report.
What the new study showed
The new study found that the benefits from eating nuts was greatest among thin people, those with high LDL cholesterol and those consuming a fat-rich diet. But enthusiasm for nuts should be restrained, Sabate said. They are highly caloric, and thus can contribute to obesity. A 3-ounce-a-day limit was recommended.
Jeannie Gazzaniga-Moloo, a spokeswoman for the American Dietetic Association who is in private practice in Sacramento, Calif., said that "nuts can be a very healthy addition to any diet," but she recommends eating somewhat less of them.
She said she suggests that her clients consume about an ounce a day of nuts -- about 22 walnuts, for example, providing about 630kj - as part of their daily diet. "They are rich in protein and dietary fiber as well as numerous proteins and in various vitamins," Gazzaniga-Moloo said.
"They should eat the nuts they enjoy," she said. "They can try a variety."
Sabata said that the type of nuts eaten doesn't seem to matter. The study found essentially the same results for walnuts, almonds, peanuts, pecans, hazelnuts, macadamias and pistachios.
"Nuts are a matrix of healthy nutrients, and the most obvious reason for the cholesterol-lowering effect is their unsaturated fat content," Sabate said. "Nuts also contain fiber, vegetable protein, phytoesterols and other antioxidants."
The best evidence for the beneficial effect of nuts, though, has come from studies of walnuts and almonds, he added. - (HealthDay News, May 2010)
Nuts in a nutshell