Jennifer Corbett Dooren
More research backing up the cholesterol-lowering benefits of eating nuts indicates that for most people, consuming two handfuls of nuts a day appears to work better than one.
The findings apply to tree nuts such as walnuts, almonds, pistachios, macadamias, hazelnuts and peanuts.
Although peanuts actually belong to the legume family, they are considered to have many of the same nutritional components as walnuts, almonds and other tree nuts.
Researchers found that, for the average person, about two servings of tree nuts did a better job of reducing blood cholesterol and triglycerides than one serving. Researchers who examined the results of 25 previous studies on the health effects of nut consumption found a dose-related improvement in participants' blood-lipid levels.
The results are published this week in the Archives of Internal Medicine.
The lead author of the latest research, Joan Sabaté, says the study "confirms that nuts, indeed, lower cholesterol." A professor and the chairman of the department of nutrition at Loma Linda University, in Loma Linda, Calif., Dr. Sabaté was among the group of researchers that first linked nut consumption to a lower risk of heart attack several years ago.
That finding and others led the Food and Drug Administration in 2003 to allow processors to state on labels that "eating 1.5 ounces per day of most nuts ... as part of a diet low in saturated fat and cholesterol may reduce the risk of heart disease."
Dr. Sabaté said the research indicated that for the average person, a slightly higher amount of nuts—about 2.4 ounces, or two servings—does a better job than one serving of lowering cholesterol and triglycerides, another type of fat in the blood.
Still, he said, "we do not need many to get the benefit." One serving of almonds is about eight nuts; a serving of smaller nuts such as peanuts is about 15 to 20 nuts.
Dr. Sabaté's analysis involved nearly 600 people with high or normal blood cholesterol levels. None of the study participants were taking cholesterol-lowering medications.
The analysis compared a control group with two groups assigned to consume two different quantities of nuts.
People in one of the nut groups consumed an average of 67 grams of nuts, or about 2.4 ounces, per day.
These people had an average reduction in total blood cholesterol concentration of 5.1%, and a reduction in low-density lipoprotein, or so-called LDL or "bad" cholesterol, of 7.4%.
For the people who consumed about 1.5 ounces of nuts, total cholesterol fell by 3.2%, while "bad" cholesterol fell by 4.9%—suggesting a dose-related response.
Those who consumed about one ounce daily of nuts, total cholesterol fell by 2.8% while LDL cholesterol fell by 4.2%.
Significantly, however, the drops in cholesterol weren't seen in people considered obese—a new finding.
More studies are needed to understand why nuts are less effective at lowering blood cholesterol concentration among obese people, the researchers said.
Dr. Sabaté said the biggest improvement in blood lipid levels were seen among people who started out with higher cholesterol levels, as well as among those who consumed a "Western" diet of high-fat meats, dairy products and refined grains, compared with people consuming a "Mediterranean" diet emphasizing whole grains, lots of fruits and vegetables, fish and relatively little red meat.
"For the general population consuming a Western diet, the incorporation of nuts into their daily diet will result in greater improvement of blood lipid levels than for individuals already following a healthy Mediterranean or low-fat diet," researchers wrote.
Of the 25 studies, about two-thirds of them involved almonds or walnuts. The other one-third of studies looked at either macadamia, pistachio, hazelnuts or peanuts. The studies didn't include pine nuts or Brazil nuts.
The study was funded by Loma Linda University in California and by the International Tree Nut Council Nutrition Research and Education Foundation, an international group that represents the tree nut industry.
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