Nuts to you! Good for your heart, but watch your waistline

Nutrition Action Healthletter, Nov, 2005 by David Schardt

Seventh-day Adventists have a lower risk of heart disease. In 1992, researchers at Loma Linda in California found one reason why.

Among the 31,000 Adventists studied, those who ate nuts more than four times a week were half as likely to die of a heart attack as those who ate nuts less than once a week. (1)

"Everybody was quite skeptical about whether we could generalize the findings to other population groups," explains Penny Kris-Etherton of Pennsylvania State University. Kris-Etherton serves on the American Heart Association's Nutrition Committee. Her research on nuts is funded in part by the walnut industry.

"People said that Seventh-day Adventists aren't like typical Americans," Kris-Etherton recalls. "They don't drink, they don't smoke, they're mostly vegetarian, they have completely different lifestyles."

But four years later, "we were pleasantly surprised when the Iowa Women's Health Study found essentially the same benefit."

Women who ate nuts or seeds more than four times a week were 40 percent less likely to die of coronary heart disease than similar women who didn't eat nuts. (2)

Other studies agreed. Among the 86,000 women in Harvard's Nurses' Health Study, those who ate at least five ounces of nuts a week were 35 percent less likely to be diagnosed with coronary heart disease than those who ate less than one ounce of nuts a month. (3)

And in the Physicians' Health Study, men who ate nuts at least twice a week had half the rate of sudden cardiac death as men who rarely or never ate nuts)

Nuts for All

What's striking, says Kris-Etherton, is that the lower risk of heart disease in nut eaters seems to apply to every group that researchers have studied: male and female, black and white, and all adult age groups. "Even the oldest of the old, those over 80 years of age, benefit from nuts, although not quite to the same degree," she says.

However, the studies from Harvard and elsewhere looked at people who were already eating nuts on their own. So researchers couldn't tease out whether the nuts--or something else about the people who eat nuts--protect them against heart disease.

Solution: give people nuts to eat and wait to see what happens. Since 1993, two dozen studies have done that with peanuts, walnuts, almonds, macadamia nuts, pecans, pistachios, and hazelnuts.

"The studies have consistently shown that diets containing nuts, nut oils, or nut butters lower LDL ["bad"] cholesterol levels by about l0 to 15 points," says Kris-Etherton. Why? Probably because nuts are high in polyunsaturated and monounsaturated fats and contain naturally occurring cholesterol-lowering compounds called plant sterols, says Kris-Etherton.

In 2003, the Food and Drug Administration approved this "qualified" health claim for seven kinds of nuts: "Scientific evidence suggests but does not prove 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."

(The claim says "does not prove" because the evidence isn't definitive. In fact, a 1990 law requires the FDA to allow health claims only when there is "significant agreement" among scientists. Nevertheless, since 2002, the FDA has allowed claims based on less-definitive science, as long as they include a disclaimer like "does not prove." Ironically, new consumer research by the FDA itself found that many people misinterpret those kinds of disclaimers.)

Watch Your Waist

"Nuts are calorically dense and they're easy to overeat," says Kris-Etherton. An ounce of most nuts--around 20 almonds, 15 cashews, or 10 walnut halves, for example--delivers 170 to 180 calories (see "Go Nuts").

When the news broke that nuts might reduce the risk of heart disease, nutritionists worried about what would happen to an already chubby nation if people started scarfing down bags and cans of nuts to lower cholesterol.

Studies have shown that people consume more calories when offered foods or meals that are caloriedense. (5)

But nut eaters aren't more likely to be overweight. "None of the population studies of people who include nuts in their diets show that they weigh more," says Kris-Etherton.

In fact, in studies of Seventh-day Adventists and 86,000 nurses, those who regularly ate nuts weighed less than those who didn't. (1,3)

But it's possible that nut eaters do other things that help keep them slim. So researchers have fed nuts to people and put them on the scale.

In research funded by the almond industry, scientists at Loma Linda University gave 81 middle-aged men and women 1 1/2 to 2 1/2 ounces (about 320 calories' worth) of almonds to eat every day, but gave them no further instructions about whether to eat the nuts instead of--or in addition to--other foods. (6)

After six months, the women gained an insignificant 0.2 pounds, but the men gained an average of 1.4 pounds.

If the men kept gaining weight, the researchers warned, "it would clearly become biologically significant, but only longer term studies can decide this question." The nut industry has yet to fund that research.