Harvard Study Shows Half Serving of Peanut Butter or Full Serving of Peanuts Eaten Daily Significantly Cuts Risk of Type 2 Diabetes

Nov 26, 2002

Harvard School of Public Health researchers report that consuming a half serving (one tablespoon) of peanut butter or a full serving of peanuts or other nuts (an ounce), five or more times a week is associated with a 21% and 27% reduced risk of developing type 2 diabetes, respectively. This ground-breaking study is published in the November 27, 2002, Journal of the American Medical Association.

The study shows women who eat five tablespoons of peanut butter each week can reduce their risk of developing type 2 diabetes by over 20%. Further, the relationship between consuming peanut butter, peanuts and other nuts and type 2 diabetes is linear — higher consumption provided a greater protective effect. The group of women consuming a half serving of peanut butter or a full serving of peanuts and other nuts one to four times per week had a 16% reduced risk of developing the disease. This large population study includes over 83,000 female nurses who were followed for an average of 16 years in the Brigham and Women’s Hospital-based Nurses’ Health Study. The women in the study completed food frequency questionnaires approximately every four years between 1980 and 1996, and had no history of diabetes, cardiovascular disease, or cancer.

Frank Hu, MD, PhD, Associate Professor of Nutrition and Epidemiology at Harvard School of Public Health and an author of the study writes in the paper, “Our findings suggest potential benefits of higher nut and peanut butter consumption in lowering the risk of type 2 diabetes in women. To avoid increasing caloric intake, regular nut consumption can be recommended as a replacement for consumption of refined grain products or red or processed meats.” It is easy to incorporate a small amount of peanut butter or peanuts into healthful diets each day. Use peanut butter instead of butter or cream cheese, or snack on peanuts or mixed nuts instead of rice cakes or crackers to satisfy hunger.

According to the US Center for Disease Control and Prevention, rates of type 2 diabetes have tripled in the last 30 years. Over 17 million people in the United States alone have diabetes, while 16 million more are at high risk of developing the disease.

These findings may provide real benefits for Americans, who each consume an average of six pounds of peanuts and peanut butter each year. Recent US Department of Agriculture data shows that 68% of the “nuts” eaten in the United States are peanuts and peanut butter, about 6% are almonds, 6% are coconuts, 5% are pecans, 5% are walnuts, and 10% are all other nuts combined. (1) This data is consistent with an earlier study by Harvard researchers that shows that about half of the “nuts” eaten by women in the Nurses’ Health Study were peanuts. (2)

Other large population studies, such as the Adventists Health Study, the Iowa Women’s Health Study and the Physicians Heath Study, all show a linear relationship between cardioprotective benefits and peanut butter, nut and peanut consumption. (3-5) These studies examined the eating patterns of both men and women and found that small, frequent servings of peanut butter, nuts, and peanuts can reduce the risk of heart disease by 25-50 percent. A growing database of clinical studies indicates that part of the beneficial effect of peanut butter, nuts, and peanuts may be due to their fatty acid composition, particularly when they replace food sources of saturated fatty acids, as well as refined carbohydrates, in the diet.

Peanut butter and peanuts contain mainly good unsaturated fat and are low in saturated fat, characteristics which are associated with lower risk of type 2 diabetes. USDA research shows that all peanut butters, including commercial and natural brands, contain at least 90% peanuts, have a very small amount of salt and sugar for taste, and have undetectable levels of trans fats even though labels list partially hydrogenated oil as a minor ingredient. (6)

In addition to unsaturated fat, other components of peanut butter, nuts and peanuts such as fiber and magnesium decrease insulin resistance and have been inversely associated with risk of type 2 diabetes. Peanuts have more plant protein than any other nut. They are also rich in vitamin E, folate, potassium, zinc, phytosterols and antioxidants, which are thought to be important to health.

The study was funded by the National Institutes of Health.



1. USDA Center for Nutrition Policy and Promotion. (2000 December). Nutrition Insights: The Role of Nuts in a Healthy Diet. Washington, DC. Retrieved January 30, 2001. www.usda.gov/cnpp

2. Hu, F.B.; Stampfer, M.J.; Manson, J.E.; Rimm, E.; Colditz, G.A.; Rosner, B.A.; Speizer, F.E.; Hennekens, C.H.; Willett, W.C. Frequent Nut Consumption and Risk of Coronary Heart Disease in Women: Prospective Cohort Study. British Medical Journal. 1998;317:1341-5.

3. Prineas, R.J.; Kushi, L.H.; Folsom, A.R.; Bostick, R.M. Letter to the Editor. New England Journal of Medicine. 1993;329:359.

4. Fraser, G.; Sabate, J.; Beeson, L.W.; Strahan, M.T. A Possible Effect of Nut Consumption on Risk of Coronary Heart Disease. Arch Intern Med. 1992; 152:1416-24.

5. Albert, C.M., Gaziano, M., Willett, W.C., Manso, J.E. Nut Consumption and Decreased Risk of Sudden Cardiac Death in the Physicians’ Health Study. Arch Intern Med. 2002;162:1382-1387.

6. Sanders, T.H. Non Detectable Levels of Trans-Fatty Acids in Peanut Butter. Journal of Agricultural and Food Chemistry. 2001;49:2349-51.

The Peanut Institute is a non-profit organization that supports nutrition research and develops educational programs to encourage healthful lifestyles.