Many people avoid nuts, thinking they are too fattening. But research now suggests that nuts can, in fact, help with weight control. Here’s the latest on this, plus other news about nuts.
The weight of evidence
With the exception of chestnuts, nuts do contain a lot of calories—160 to 200 an ounce, most from healthy unsaturated fats. But in general, people who eat nuts regularly tend to weigh less than those who don’t—or at least they don’t weigh more, population studies show. For instance, a Spanish study of nearly 9,000 people, reported in Obesity last year, found that those who ate nuts at least twice a week were less likely to gain weight over 28 months than those who never or rarely ate nuts.
Even when people add nuts to their usual diets, they don’t seem to gain much, if any, weight. In a small study from Purdue University last year, women who added 344 calories worth of almonds a day to their diets—without purposefully cutting back on calories elsewhere or exercising more—did not gain weight after 10 weeks. Similar findings have been reported with walnuts and peanuts. Fewer studies have looked at whether nuts can actually help you lose weight, but one found that a low-calorie diet that included almonds led to more weight loss than a same-calorie, nut-free diet.
A 2007 review from Australia sums it up: When added freely to a diet, nuts cause less weight gain than would be predicted—and when added to a calorie-controlled diet, they don’t cause weight gain and may sometimes make weight loss easier.
What is it about nuts? The fiber and protein in nuts help make you feel full longer, so you are less hungry—and presumably eat less—later. And some (but not all) studies suggest that nuts may slightly increase calorie burning. Interestingly, some research has also found that not all the fat in whole nuts is absorbed—from 4 percent to 17 percent passes out of the body undigested.
Good for your heart
Studies have consistently linked nuts to a markedly reduced risk of heart disease, largely because they have a favorable effect on blood cholesterol. According to a review of studies in the Journal of Nutrition in 2005, eating about two to three ounces of nuts most days of the week—in particular almonds, pecans, peanuts and walnuts—may significantly lower total and LDL ("bad") cholesterol.
In some cases, nuts have been shown to increase HDL ("good") cholesterol. In recent studies walnuts also improved blood vessel health, while pistachio and macadamia nuts favorably altered risk factors for heart disease in other ways. A study several years ago linked nuts to a reduced risk of Type 2 diabetes.
A heart-healthy explanation: The unsaturated fats in nuts can improve blood cholesterol levels, especially when substituted for foods high in saturated fat, such as meat and cheese. Other nutrients and substances in nuts also have heart-health benefits, including B vitamins, potassium, copper, magnesium, vitamin E, fiber (much of it soluble), arginine (an amino acid that helps relax blood vessels), sterols (which help lower cholesterol) and a range of other phytochemicals. The Food and Drug Administration (FDA) allows most nuts to carry a "qualified" health claim—that is, one hedged with qualifiers—stating that 1.5 ounces a day may help reduce the risk of heart disease.
Not so nutty advice
For people who don’t eat meat or want to consume less, nuts are one of the best plant sources of protein. The United States Department of Agriculture (USDA) counts nuts in the "meat and bean" group of its food pyramid.
Though nuts are healthful and may help you control your weight, don’t go overboard—limit yourself to an ounce or two a day. One small handful is about an ounce. Watch out for the sodium in packaged nuts; unsalted varieties are widely available.
Nut butters, including almond, cashew and, of course, peanut butter, have the same nutritional advantages as the nuts themselves and are a healthier sandwich filling than cheese and most meats.
The health scoop on some popular nuts
- Almonds are richest in vitamin E and calcium (35 percent and 8 percent, respectively, of the daily recommended amount per ounce.
- Brazil nuts are the best dietary source of selenium. Just one medium nut a day supplies all you need. Eating two or three a day provides about 200 micrograms, the amount found to lower the risk of prostate cancer in some studies.
- Cashews are richest in copper and zinc (30 percent and 10 percent, respectively, of the daily recommended amount.
- Macadamia nuts have the most calories (205 per ounce) and most fat (21 grams, 17 grams unsaturated). Chestnuts have the least (70 calories and less than one gram of fat).
- Peanuts are technically legumes but are classified with nuts because of their shared nutritional (and physical) qualities. They contain resveratrol, a phytochemical also found in grapes and red wine that may have health benefits, are richest in arginine, and have the most protein.
- Like all nuts, hazelnuts (filberts), pecans and pistachios provide some iron, magnesium, thiamin and other nutrients. An ounce of hazelnuts provides almost a day’s worth of manganese.