The Peanut Institute
HomeHealthy DietsNutrition Basics Scientific ResearchPeanut FAQs
RecipesWhat's NewEducational MaterialsAbout The Peanut Institute

Scientific Research

Take Another Look at Peanuts -- Nutrition Scientists Are...
Highlights from nut-related research


Some nutrition scientists are now finding that the type of fat in the diet may be more important than the amount of fat. Numerous research studies have shown that diets high in mono- and polyunsaturated fats and low in saturated fat can be heart-healthy. Studies of large populations, as well as smaller controlled studies, show that people who consume a diet high in monounsaturated fat from food sources such as olive oil, peanuts, and nuts are inclined to have lower incidences of heart disease. Peanuts and peanut butter also add other valuable nutrients to the diet, such as vitamin E, folate (folic acid), fiber, plant protein, and many minerals that may protect against heart disease and some cancers.

Peanuts in a Heart-Healthy Diet: Recently Reported Research on Peanuts, Peanut Butter and Peanut Products

  • A study at Penn State tested the effects of two calorically-controlled diets that were low in saturated fat and cholesterol on weight loss and cardiovascular disease. One of the diets was low-fat (less than 20% calories from fat) and one was higher in total fat (35% of calories from fat, which was mainly monounsaturated). Both groups lost an average of two pounds per week over the six week study period and preliminary results show that both diets lowered total and LDL cholesterol, two known risk factors for cardiovascular disease (1). According to Dr. Penny Kris-Etherton, Distinguished Professor of Nutrition at Penn State and principle investigator, "There is now compelling evidence that a high-monounsaturated fat, 'Mediterranean-style' diet is as good as a low-fat diet for weight loss and improving cardiovascular risk factors. Consumers should understand that 'fat-free' does not always translate into weight loss and that healthy diets can include favorite foods, such as peanuts and peanut butter, while promoting weight loss and weight maintenance."

  • These results compliment a previous study conducted by Dr. Kris-Etherton in which healthy subjects consumed one of five types of diets: a low-fat diet; one including olive oil; one including peanuts and peanut butter; one including peanut oil; and a typical American diet. Results show that the diet including peanuts and peanut butter, the one including peanut oil, and the diet including olive oil (all low in saturated fat and cholesterol, and high in monounsaturated fat) lowered total cholesterol and LDL (bad) cholesterol. Furthermore, each of these three diets lowered triglyceride levels, but did not lower the beneficial HDL cholesterol. The low-fat diet was successful in lowering LDL cholesterol levels, but it also lowered "good" HDL cholesterol and increased triglyceride levels. The "peanut diets" included small amounts of peanut products daily: a little peanut butter on a bagel, peanuts as an afternoon snack, and peanut oil in salad dressing (2).

  • According to research at Harvard Medical School and Brigham and Women's Hospital in Boston, almost three times as many people were able to stick to a higher fat diet that included peanuts and peanut butter during an 18 month weight-loss study. One hundred and one overweight men and women were assigned to either of two weight loss diets: 1) a low fat diet and 2) a higher monounsaturated-fat, "Mediterranean-style" diet. They found that subjects on the "Mediterranean style" diet fared better throughout the study period. They lost more weight and were able to stick to the diet (3).

  • Dr. Richard Mattes, professor of Foods and Nutrition at Purdue University found that when 500 calories of peanuts were added to subjects' regular diets, substituted in the diet for other fat, or eaten freely, the results were the same-- the men and women automatically compensated for most of the additional calories and they spontaneously commented on the high satiety of the peanuts. Those who either added peanuts to their regular diet or substituted peanuts for other fats had the added benefit of significantly lowering their triglyceride levels (TG), a known risk factor for cardiovascular disease (CVD) (4). This finding is consistent with an earlier study at Purdue that showed that snacks of peanuts and peanut butter produced more eating satisfaction and feelings of fullness than other high-carbohydrate snacks, such as rice cakes. Furthermore, subjects who were fed the peanut snacks self-adjusted their caloric intakes; they did not add extra calories to their daily diets (5).

  • Another research study at Penn State found that peanut eaters consistently tend to have higher levels of key nutrients and overall healthier diets than their non-peanut eating counterparts. Furthermore, the body mass index (or BMI, a measure health professionals use in estimating overweightness and chronic disease risk) of peanut eaters was found to be favorable to that of non-peanut eaters (6).

  • New research from the Harvard School of Public Health suggests that eating even just two servings of peanuts and nuts per week can decrease the risk of having another coronary event among people who have survived a heart attack. Researchers followed participants in the CARE trial over 4.2 years and found that compared to those who rarely or never consumed them, subjects who consumed two or more servings of peanuts and nuts per week decreased their risk of heart disease by 25% (7).

  • A phytosterol, beta-sitosterol (SIT), which has previously been shown to inhibit cancer growth has been identified in peanuts and peanut products (8). SIT may offer protection from colon, prostate and breast cancer, all of which tend to occur at higher rates in Americans than in other populations. Researchers at the State University of New York at Buffalo examined the SIT content of peanuts, peanut butter, peanut flour and peanut oil and found that the content varied from 44 mg SIT/100 gm (peanut flour) to 191 mg SIT/100 gm (unrefined peanut oil). Snack peanuts contain 160 mg SIT/100 gm and peanut butter contains approximately 120 mg SIT/100 gm. The amount of protective SIT in unrefined peanut oil is comparable to that of soybean oil (183 mg SIT/100 gm).

  • In a study published in the November 1998 British Medical Journal, researchers at Harvard School of Public Health found that in the population studied, "frequent consumption of peanuts and nuts was associated with a lowered risk of coronary heart disease (CHD)." (9) The eating habits and health outcomes of over 86,000 women, age 34-59, were followed for almost 20 years. After adjusting for age, smoking, and other known risk factors for CHD, women who ate more than five servings of nuts and peanuts per week decreased their risk of heart disease by about one third, compared to women who rarely or never ate nuts. These results persisted even after adjusting for intakes of dietary fats, fiber, vegetables, and fruits; use of alcohol; use of vitamin E and multivitamin supplements; body mass index; and exercise.

  • Preliminary results of the Physicians Health Study were announced at the 1998 American Heart Association Conference. Researchers studied the diets and occurrence of cardiac death in over 22,000 male physicians and found results that are similar to the Nurses Health Study. In this population, as nut consumption increased, the risk of cardiac death and sudden death decreased (10). This inverse relationship between cardiac death and consumption of nuts and peanuts persisted after controlling for age, exercise, hypertension, cholesterol, smoking, diabetes, use of alcohol, and other dietary habits.

    Earlier Research Studies on Peanuts and Nuts in the Diet

  • The DASH Diet, an eating plan that has been clinically proven to lower blood pressure in hypertensive men and women, may also be effective in preventing hypertension, according to a study in the New England Journal of Medicine (11). While the DASH Diet is an entire eating plan, a significant element is that it recommends eating four to five servings from the nuts, seeds, and legumes group each week.

  • A study using peanuts was conducted at the University of Florida in the early 1990's. It found that a low-fat diet with a high proportion of monounsaturated fats, in this case from high-oleic peanuts, reduced cholesterol levels in women (12).

  • Results from the Iowa Women's Study, conducted on over 34,000 post-menopausal women with no cardiovascular disease, also found that higher levels of nut consumption were related to lower risk of dying from heart disease (13).

  • Different types of clinical studies using a variety of nuts, such as peanuts, macadamia and walnuts, demonstrate that consumption of nuts can lower LDL cholesterol levels and possibly reduce the risks contributing to both fatal and non-fatal coronary heart disease (12, 14-17).

  • Another study in Australia found that subjects who consumed diets rich in monounsaturated fats, mainly from peanuts, experienced a larger decline in LDL cholesterol as compared to the low-fat diet. Instead of raising triglyceride levels as on the low-fat diet, the peanut-enriched diet eaters lowered their triglyceride levels (18).

  • A landmark study of approximately 27,000 Seventh-Day Adventists in California was one of the first to suggest that nut-eaters are a healthy group. Researchers looked at the relationship between 65 different foods and coronary heart disease. Out of all the foods studied, nuts by far had the strongest protective effect on the risk of having a heart attack or dying of heart disease. A further diet analysis showed that 32 percent of the nuts consumed by study participants were peanuts.

  • Researchers note the favorable fatty acid profile of peanuts and nuts -- low in saturated fat and high in mono- and polyunsaturated fats -- as one possible explanation for their protection against heart disease. This particular study found a linear relationship between risk of CHD and consumption of nuts. People eating nuts more than 5 times a week decreased risk of heart disease by over 50 percent; those eating nuts 1-4 times per week decreased their risk by 27 percent (19).

    The Heart Healthfulness of Unsaturated Fats

  • In an earlier analysis of the data from the Nurses Health Study, researchers at Harvard found that the risk of coronary disease increased with the amount of saturated fat in the diet. It is estimated that the replacement of 5 percent of energy from saturated fat with energy from unsaturated fat would reduce risk of heart disease by 42 percent (20).

  • Analyses from the Harvard Nurses' Health Study further confirm the results from the Seven Countries Study which suggests that the type of fat consumed in the diet may be as important as the amount of fat consumed (21).

    The Heart Healthfulness of Vitamin E

  • Beyond fat in the diet, researchers look at a variety of vitamins, minerals and phytochemicals and their effects on heart disease. In a study of over 34,000 women, as intakes of vitamin E from food sources increased, the risk of death from heart disease decreased (22).

  • The Health-Professionals Follow-up Study conducted from 1986-1990 on almost 40,000 men and the Nurses' Health Study conducted from 1976-present over 80,000 women found the same inverse correlation between vitamin E and heart disease. Namely, higher intakes of vitamin E were associated with a lower risk of heart disease (23, 24).

    The Heart Healthfulness of Folate (Folic Acid)

  • Researchers have found that an accumulation of the amino acid homocysteine in the blood can cause a variety of effects that promote heart disease, such as damaging arteries and building up plaque in artery walls. Studies have shown that people with high blood levels of homocysteine are at higher risk for heart attack. Higher intakes of folate lead to lower levels of homocysteine since folate is involved in the removal of the amino acid (25, 26).

  • In further analysis of the Nurses' Health Study, higher intakes of folate were associated with lower risk of heart disease, regardless of the folate source (27).

    The Heart Healthfulness of Plant Foods and Phytochemicals

  • Populations in Mediterranean and many Asian countries have been shown to have lower rates of heart and other chronic diseases. There are numerous explanations for this trend; one is that their diets consist largely of plant foods, which naturally contain very little saturated fat and cholesterol and high levels of fiber, vitamins, minerals and phytochemicals (28).

  • Resveratrol, the phytochemical found in red wine and grape skins, has been associated with a reduced risk of cardiovascular disease and some cancers. Dr. Tim Sanders, of the USDA/Agricultural Research Service, identified resveratrol in samples of peanuts. Peanuts contain 1.7-3.7 ug/g of resveratrol, compared to 0.6-8.0 ug/ml in red wines (29).

  • Research announced in the December 1998 American Journal of Clinical Nutrition found that resveratrol has other positive effects (aside from its antioxidant characteristics) on cell adhesion, or sticking to artery walls (30). Resveratrol was shown to have a positive effect on cell adhesion molecules, thereby decreasing the risk of clogged arteries.

  • Dr. John Pezzuto, at the University of Illinois, Chicago, recently identified resveratrol as the most impressive and powerful of thousands of potential cancer-fighting chemicals identified in his lab (31). This plant chemical has been found to be effective against the initiation, promotion, and progression of cancer.

    References

    1. Pearson, T.A.; Kirwan, J.P.; Maddox, D.; Fishell, V.; Juturu, V.; Kris-Etherton, PM. Weight loss and Weight Maintenance: Effects of High MUFA VS. Low Fat Diets on Plasma Lipids and Lipoproteins. Presentation, Experimental Biology '99. April 19, 1999.

    2. Pearson, T.A.; Etherton, T.D.; Moriarty K.; Reed R.; Kris-Etherton P.M. High-Monounsaturated Fatty Acid Diets with Peanuts-Peanut Butter or Peanut Oil Lower Total Cholesterol and LDL-C Identically to a Step 2 Diet But Eliminate the Triglyceride Increase. Presentation, Experimental Biology '98. April 20, 1998.

    3. McManus, K.; Antinoro, L.; Sacks, F.M . Weight Reduction: A Comparison of a High Unsaturated Fat Diet with Nuts Versus a Low-Fat Diet. Presentation, Experimental Biology '99. April 19, 1999.

    4. Lermer, C.M. and Mattes, R.M. Effects of Chronic Peanut Consumption on Body Weight and Serum Lipid Levels in Humans. Presentation, Experimental Biology '99. April 19, 1999.

    5. Mattes, R.D. and Voisard, S.K. Effects of Peanuts on Hunger and Food Intakes in Humans. Presentation, Experimental Biology '98. April 20, 1998.

    6. Eissenstat, B.; Juturu, V.; Hshieh, G.; Maddox, D.; Kris-Etherton, PM. Impact of Consuming Peanuts and Peanuts Products on Energy and Nutrient Intakes of American Adults. Presentation, Experimental Biology '99. April 19, 1999.

    7. Brown, L.; Rosner, B.A.; Willett, W.C.; Sacks, F.M. Nut Consumption and Risk of Recurrent Coronary Heart Disease. Presentation, Experimental Biology '99. April 19, 1999.

    8. Awad, A.B.; Chan, K.; Downie, A.; Fink, C.S. Anticancer Properties. Presentation, Experimental Biology '99. April 19, 1999.

    9. 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.

    10. Albert, C.M.; Willet, W.C.; Manson, J.E.; Hennekens, C.H. Nut Consumption and the Risk of Sudden and Total Cardiac Death in the Physicians Health Study. Abstract, American Heart Association. November 9-11, 1998.

    11. Appel, LJ et. al. A Clinical Trial of the Effects of Dietary Patterns on Blood Pressure. The New England Journal of Medicine. 1997;336(16):1117-1123.

    12. O'Byrne, D.J.; Knauff, D.A.; Shireman, R B. Low-Fat Monounsaturated Rich Diets Containg High-Oleic Peanuts Improve Serum Lipoprotein Profiles. Lipids. 1997;32:687-95.

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

    14. Abbey, M.; Noakes, M.; Belling G.; Nestel, P. Partial Replacement of Saturated Fatty Acids with Almonds or Walnuts Lowers Total Plasma Cholesterol and Low-Density-Lipoprotein Cholesterol. American Journal of Clinical Nutrition. 1994;59:995-9.

    15. Curb, J.D.; Wergowski, G.; Dobbs, J.; Abbott, R.D.; Huang, B. Comparison of Lipid Levels in Humans on a Macadamia Nut Based High Monounsaturated Fat Diet and a High Fat Typical American Diet. Presentation, American Heart Association, Scientific Conference on Efficacy of Hypocholesterolemic Dietary Interventions. 1995;3-5.

    16. Sabate, J.; Fraser, G.; Burke, K.; Knutsen, S.; Bennett, H., Lindstead, K. Effect of Walnuts on Serum Lipid Levels and Blood Pressure in Normal Men. New England Journal of Medicine. 1993;328:603-7.

    17. Dreher, M.L.: Maher, C.; Kearney, P. The Traditional and Emerging Role of Nuts in Healthful Diets. Nutrition Reviews. 1996;54:241-5.

    18. Colquhoun, D.M.; Hicks, B.J.; Somerset, S.; Hamil, C. Comparison of the Effects of a High-Fat Diet Enriched with Peanuts and a Low-Fat Diet on Blood Lipid Profiles. Abstract, American Heart Association. 1996;733.

    19. Fraser, G.; Sabate, J.; Beeson, L.W.; Strahan, M.T. A Possible Effect of Nut Consumption on Risk of Coronary Heart Disease, Archives of Internal Medicine. 1992; 152:1416-24.

    20. Hu, F.B.; Stampfer, M.J.; Manson, J.E.; Rimm, E.; Colditz, G.A.; Rosner, B.A.; Hennekens, C.H.; Willett, W.C. Dietary Fat Intake and the Risk of Coronary Heart Disease in Women. New England Journal of Medicine. 1997;337:1491-9.

    21. Keys, A. Seven Countries: A Multivariate Analysis of Death and Coronary Heart Disease. Harvard University Press. 1980.

    22. Kushi, L.H.; Folsom, A.R.; Prineas, R.J.; Mink, P.J.; Wu, Y.; Bostick, R.M. Dietary Antioxidant Vitamins and Death From Coronary Heart Disease in Post Menopausal Women. New England Journal of Medicine. 1996;334:1156-62.

    23. Rimm, E.; Stampfer, M.J.; Ascherio, A.; Giovannucci, E.; Colditz, G.A.; Willett, W.C. Vitamin E Consumption and the Risk of Coronary Heart Disease in Men. New England Journal of Medicine. 1993;328:1450-6.

    24. Stampfer, M.J.; Hennekens, C.H.; Manson, J.E.; Colditz, G.A.; Rosner, B.; Willett, W.C. Vitamin E Consumption and the Risk of Coronary Heart Disease in Women. New England Journal of Medicine. 1993;328:1444-9.

    25. Ubbink, J.; Vermaak, H.; van der Merwe, A.; Becker, P.JH.; Delport, R.; Potgieter, H.C. Vitamin Requirements for the Treatment of Hyperhomocysteinemia in Humans. Journal of Nutrition. 1994;124:1927-33.

    26. Boushey, C.; Beresford, S.; Omenn, G.S.; Motulsky, A.G. A Quantitative Assessment of Plasma Homocysteine as a Risk Factor for Vascular Disease. Journal of the American Medical Association. 1995;274:1049-1057.

    27. Rimm, E.; Willett, W.C.; Hu, F.B.; Sampson, L.; Colditz, G.A.; Manson, J.E.; Hennekens, C.H.; Stampfer, M.J. Folate and Vitamin B6 From Diet and Supplements in Relation to Risk of Coronary Heart Disease Among Women. Journal of the American Medical Association. 1998;279:359-364.

    28. Kushi, L.H.; Lenart, E.B.; Willett, W.C. Health Implications of Mediterranean Diets in Light of Contempory Knowledge. 1. Plant Foods and Dairy Products. American Journal of Clinical Nutrition. 1995;61(suppl):1407S-15S.

    29. Sanders, T.H. and McMichael, R.W. Occurrence of Resveratrol in Edible Peanuts. Presentation, American Oil Chemists Society, Las Vegas, Nevada. 1998.

    30. Ferrero et al. Activity in vitro of Resveratrol on Granulocyte and Monocyte Adhesion to Endothelium. American Journal of Clinical Nutrition. 1998;68(6):1208-15.

    31. Jang M.; Cai L.; Udeani, G.O.; Slowing, K.V.; Thomas, C.F.; Beecher, C.W.; Fong, H.H.; Farnsworth, N.R.; Kinghorn, A.D.; Mehta, R.G.; Moon, R.C.; and Pezzuto, J.M. Cancer Chemopreventive Activity of Resveratrol, a Natural Product Derived from Grapes. Science. 1997;275:218-20.

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



    • © The Peanut Institute 1999. All rights reserved.