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Harvard Commentaries
Harvard Commentaries
Reviewed by the Faculty of Harvard Medical School

Man to Man Man to Man

Nuts and Your Health -- Cracking Old Myths

February 19, 2014

By Harvey B. Simon M.D.

Harvard Medical School

Whatever people think of Harvard, few would accuse its heavy-duty scientists of being health nuts. But Harvard researchers may deserve that designation. After all, they have teamed up to show that nuts are actually healthy, especially for men at risk for heart disease.

Harvard Study Results

A 2013 report from Harvard Medical School and the Harvard School of Public Health looked at how eating nuts affects the health of men and women. The study evaluated 42,498 men enrolled in the Health Professionals Follow-up Study and 76,464 women enrolled in the Nurse's Health Study. None of the participants had known heart disease, cancer or stroke when they enrolled in the studies. Researchers began tracking the subjects in the early 1980s. And they continue to follow many of the volunteers today.

What's in a Name?
Peanuts, the most popular nuts of all — are not technically nuts.

Nuts are one-seeded fruits that grow on trees. Peanuts grow in the ground. They are legumes, members of the bean and pea family of plants. Peanuts do have a tough outer shell, like trun nuts do. And they share the nutritional characteristics of nuts.

In fact, the Harvard study found that peanuts were as beneficial as true nuts. But the technical distinction does have one important practical consequence: Most people who are allergic to peanuts can safely eat tree nuts.

Each subject submitted detailed diet and health information at the start of the study and every 2 to 4 years thereafter. This continued for up to 30 years. According to the results, people who ate nuts fared better than those who did not. And the more nuts eaten, the better the results. 

  • People who ate just one portion of nuts a week enjoyed a 7% lower death rate than people who didn't eat nuts.
  • Eating nuts 5 or 6 times a week was linked to a spectacular 20% reduction in the death rate.
  • Nuts appeared to offer protection from a wide range of problems, including heart disease, cancer and lung disease.  And the results held up even after smoking, drinking, body fat, exercise, vitamins and other dietary factors were taken into account.

It's not as nutty as it sounds: Eating nuts promotes good health.

All the subjects in the Harvard study were health care professionals. But do nuts reduce the risk of illness risk in other population groups?

They do.

Scientists have reported that nuts appear to protect people as diverse as Seventh Day Adventists in California, women in Iowa, healthy men and women in the Netherlands, and heart attack survivors in India.

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How Nuts Help

Doctors don't know for sure, but they have several theories.

  • Nuts help reduce blood cholesterol levels, either by replacing other, harmful foods or by lowering cholesterol on their own.  
  • Nuts are high in fat. But these are "good" fats, which may reduce the risk of abnormal heart pumping rhythms that can sometimes cause sudden cardiac death.  
  • According to a Spanish study, nuts improve endothelial function, allowing arteries to widen when tissues need more oxygen.

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What's in Nuts?

Nuts pack many nutrients in a small package.

  • Nuts have no cholesterol. And they contain only tiny amounts of saturated fat. Instead, they have lots of mono- and polyunsaturated fats that resemble the fats in olives and other vegetables that may help protect the heart.
  • Nuts may also help by providing vitamin E and other antioxidants.
  • They are also rich in protein, B vitamins, potassium, magnesium and other minerals.
  • Nuts are an excellent source of fiber, which reduces the risk of heart disease.

Before you go nuts, keep in mind that:

  1. Nuts are high in fat, which makes them high in calories. All fats, whether they are harmful saturated fats or healthful unsaturated fats, have 9 calories per gram. So unless you want to gain weight, don't add nuts to your diet without cutting a similar number of calories. Fortunately, the new Harvard study reported that people who ate nuts regularly actually gained less weight than people who didn't eat nuts.
  2. Many processed nuts that are so handy for snacks are fried in oil and/or laced with salt, which can raise your blood pressure.

Nuts can be part of a balanced, healthful diet. And they can help reduce your risk of heart disease. 

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Harvey B. Simon, M.D. is an Associate Professor of Medicine at Harvard Medical School and a member of the Health Sciences Technology Faculty at Massachusetts Institute of Technology. He is the founding editor of the Harvard Men's Health Watch newsletter and author of six consumer health books, including The Harvard Medical School Guide to Men's Health (Simon and Schuster, 2002) and The No Sweat Exercise Plan, Lose Weight, Get Healthy and Live Longer (McGraw-Hill, 2006). Dr. Simon practices at the Massachusetts General Hospital; he received the London Prize for Excellence in Teaching from Harvard and MIT.

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Bao et al. "Association of nut comsumption with total and cause-specific mortality." New England Journal of Medicine. 2013; 369: 2001.

Flores-Mateo et al. "A single consumption of high amounts of Brazil nuts improvies lipid profiles of healthy volunteers." American Journal of Clinical Nutrition. 2013; accessed online 4/26/13.

Ros and Hu. "Consumption of plant seeds and cardiovascular health: Epidemiological and clinical trial evidence." Circulation. 2013; 128:553.

Sabate et al. "Nut consumption and blood lipid levels." Archives of Internal of Medicine. 2010; 170:821

Salas-Salvado et al. "Effects of a Mediterranean diet supplemented with nuts on metabolic syndrome status." Archives of Internal of Medicine. 2008; 168:2449.

Nash and Westpfal. "Cardiovascualr benefits of nuts." American Journal of Cardiology. 2005; 95:963.

Lovejoy et al. "Effects of diets enriched in almonds on insulin action and serum lipids in adults with normal glucose tolerance or type 2 diabetes." American Journal of Clinical Nutrition. 2002;76:1000.

Jenkins et al. "Dose response of almonds on coronary heart disease risk factors: a randomized, controlled cross-over trial." Circulation 2002;106:1327.

Jiang et al. "Nut and peanut butter consumption and risk of type 2 diabetes in women." Journal of the American Medical Association. 2002;288:2554.

Curb et al. "Serum lipid effects of a high monounsaturated fat diet based on macadamia nuts." Archives of Internal Medicine. 2000;160:1154.

Zambon et al. "Substituting walnuts for monounsaturated fat improves the serum lipid profile of hypercholesterolemic men and women. A randomized crossover trial."  Annals of Internal Medicine. 2000;132:538.

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