In the not too distant past, nuts were considered unhealthy because of their relatively high fat content. In contrast, recent research suggests that regular nut consumption is an important part of a healthy diet (1). Although the fat content of nuts is relatively high (14-19 grams/ounce), most of the fats in nuts are the healthier monounsaturated and polyunsaturated fats (2) (see Table). The term “nuts” includes almonds, Brazil nuts, cashews, hazelnuts, macadamia nuts, pecans, pistachios, walnuts, and peanuts. Despite their name, peanuts are actually legumes like peas and beans. However, they are nutritionally similar to tree nuts and have some of the same beneficial properties.
Coronary Heart Disease
In large prospective cohort studies, regular nut consumption has been consistently associated with significant reductions in the risk of coronary heart disease (CHD) (3). One of the first studies to observe a protective effect of nut consumption was the Adventist Health Study, which followed more than 30,000 Seventh Day Adventists over 12 years (4). In general, the dietary and lifestyle habits of Seventh Day Adventists are closer to those recommended for cardiovascular disease prevention than those of average Americans. Few of those who participated in the Adventist Health Study smoked, and most consumed a diet lower in saturated fat than the average American. Even in this healthy living group, those who consumed nuts at least 5 times weekly had a risk of death from CHD that was 48% lower than those who consumed nuts less than once weekly and a risk of a nonfatal myocardial infarction (MI) that was 51% lower. Even in people over 83 years of age, those who ate nuts at least 5 times weekly had a risk of death from CHD that was 39% lower than those who consumed nuts less than once weekly (5). The results of a smaller prospective study of more than 3000 Black men and women those were similar (6). Those who consumed nuts at least 5 times weekly had a risk of death from CHD that was 44% lower than those who consumed nuts less than once weekly.
The cardioprotective effects of nuts were not limited to Seventh Day Adventists. In a 14-year study of more than 86,000 women participating in the Nurses’ Health Study, those who consumed more than 5 oz of nuts weekly had a risk of CHD that was 35% lower than those who ate less than 1 oz of nuts monthly (7). Similar decreases were observed for the risk of death from CHD and nonfatal MI. More recently, a 17-year study of more than 21,000 male health professionals found that those who consumed nuts at least twice weekly had a risk of sudden cardiac death that was 53% lower than those who rarely or never consumed nuts, although there was no significant decrease in the risk of nonfatal MI or nonsudden CHD death (8). The Iowa Women’s Health Study, which followed more than 30,000 postmenopausal women for 12 years, is the only published prospective study that did not observe a significant inverse association between nut consumption and CHD mortality, although a slight but significant decrease in all cause mortality was observed in those who consumed nuts twice weekly (9). Overall, the results of most prospective cohort studies suggest that regular nut consumption is associated with a substantial decrease in the risk of death related to CHD.
Results of controlled clinical trials indicate that at least part of the cardioprotective effect of nut consumption is derived from beneficial effects on serum total and LDL cholesterol concentrations (3). At least 18 controlled clinical trials have found that adding nuts to a diet that is low in saturated fat results in significantly reductions in serum total cholesterol and LDL-cholesterol concentrations in people with normal or elevated serum cholesterol. These effects have been observed for almonds (10-13), hazelnuts (14), macadamia nuts (15,16), peanuts (17,18), pecans (19), pistachio nuts (20) and walnuts (21-26). More recently, a cross-sectional study found frequent nut and seed consumption to be associated with lower serum levels of inflammatory biomarkers in a multi-ethnic population (27). Although the evidence is circumstantial, these findings suggest that compounds in nuts may lower the risk of cardiovascular disease by decreasing inflammation.
Cardioprotective Compounds in Nuts
Substituting dietary saturated fats with polyunsaturated and monounsaturated fats like those found in nuts can decrease serum total and LDL cholesterol concentrations (3). However, in some of the clinical trials, the cholesterol-lowering effect of nut consumption was greater than would be predicted from the polyunsaturated and monounsaturated fat content of the nuts, suggesting there may be other protective factors in nuts (28). Other bioactive compounds in nuts that may contribute to their cholesterol-lowering effects include fiber and phytosterols . See the table below for the unsaturated fat, fiber and phytosterol contents of selected nuts. Walnuts are especially rich in alpha-linolenic acid, an omega-3 fatty acid with a number of cardioprotective effects, including the prevention of cardiac arrhythmias that may lead to sudden cardiac death. Other nutrients that may contribute to the cardioprotective effects of nuts include folate and potassium (3, 29). The US Food and Drug Administration (FDA) has acknowledged the emerging evidence for a relationship between nut consumption and cardiovascular disease risk by approving the following qualified health claim for nuts (30): “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.” For more information on the nutrient content of nuts, search the USDA National Nutrient Database.
Energy, Fat, Phytosterols and Fiber in a 1-oz
Serving of Selected Nuts
|
||||||
Nut (1 ounce) |
Energy (kcal) |
Total fat (g) |
MUFA* (g) |
PUFA* (g) |
Phytosterols (mg) |
Fiber (g) |
Almonds |
164 |
14.4 |
9.1 |
3.5 |
34.0 |
3.3 |
Brazil nuts |
186 |
18.8 |
7.0 |
5.8 |
NA |
2.1 |
Cashews |
160 |
13.3 |
7.2 |
2.4 |
44.8 |
0.9 |
Hazelnuts |
178 |
17.2 |
12.9 |
2.2 |
27.2 |
2.8 |
Macadamia nuts |
204 |
21.5 |
16.7 |
0.4 |
32.9 |
2.4 |
Peanuts (legume) |
166 |
14.1 |
7.0 |
4.5 |
62.3 |
2.3 |
Peanut butter, smooth (2 Tbs) |
192 |
16.7 |
7.9 |
4.8 |
32.6 |
1.9 |
Pecans |
196 |
20.4 |
11.6 |
6.1 |
28.9 |
2.7 |
Pine nuts (pignoli) |
191 |
19.4 |
5.3 |
9.7 |
40.0 |
1.0 |
Pistachio nuts |
158 |
12.6 |
6.6 |
3.8 |
60.7 |
2.9 |
Walnuts, Black |
175 |
16.7 |
4.3 |
9.9 |
30.6 |
1.9 |
*MUFA, Monounsaturated Fatty Acids; PUFA, Polyunsaturated Fatty Acids
Recent results from the Nurses’ Health Study suggest that nut and peanut butter consumption may be inversely associated with the risk of type 2 diabetes mellitus (DM) in women (31). In this cohort of more than 86,000 women followed over 16 years, those who consumed an ounce of nuts at least 5 times weekly had a risk of developing type 2 DM that was 27% lower than those who rarely or never consumed nuts. Similarly those who consumed peanut butter at least five times weekly had a risk of developing type 2 DM that was 21% lower than those who rarely or never consumed peanut butter. While these findings require confirmation in other studies, they provide additional evidence that nuts can be a component of a healthy diet. Compounds in nuts that could contribute to the observed decrease in type 2 DM include unsaturated fats, fiber and magnesium.
Nut Allergies
Allergies to peanuts and tree nuts (almonds, cashews, hazelnuts, pecans, pistachios and walnuts) are among the most common food allergies, affecting at least 1% of the US population (32). Although all food allergies have the potential to induce severe reactions, peanuts and tree nuts are among the foods most commonly associated with anaphylaxis, a life-threatening allergic reaction (33). People with severe peanut or tree nut allergies need to take special precautions to avoid inadvertently consuming peanuts or tree nuts by checking labels and avoiding unlabeled snacks, candies, and desserts. See the Food Allergy and Anaphylaxis Network website for additional tips to avoiding unintentional peanut or tree nut exposure.
Regular nut consumption, equivalent to an ounce of nuts 5 times weekly, has been consistently associated with significant reductions in ccoronary heart disease (CHD) risk in epidemiological studies. Consuming 1-2 oz of nuts daily as part of a diet that is low in saturated fat has been found to lower serum total and LDL-cholesterol in a number of controlled clinical trials. Since an ounce of most nuts provides at least 160 calories (kcal), simply adding an ounce of nuts daily to one’s habitual diet without eliminating other foods may result in weight gain. Substituting unsalted nuts for other less healthy snacks or for meat in main dishes are two ways to make nuts part of a healthy diet.
| Some Potentially Beneficial Compounds in Nuts | |||
Macronutrients |
Vitamins |
Minerals |
Phytochemicals |
| Unsaturated fats | Folate | Magnesium | Fiber |
| Vitamin E | Potassium | Phytosterols | |
Written by:
Jane Higdon, Ph.D.
Linus Pauling Institute
Oregon State University
Reviewed by:
Frank B. Hu, M.D., Ph.D.
Associate Professor of Nutrition and Epidemiology
Harvard School of Public Health
Last updated 12/19/05 Copyright 2003-2008 Linus Pauling Institute
Disclaimer
The Linus Pauling Institute Micronutrient Information Center provides scientific information on health aspects of micronutrients and phytochemicals for the general public. The information is made available with the understanding that the author and publisher are not providing medical, psychological, or nutritional counseling services on this site. The information should not be used in place of a consultation with a competent health care or nutrition professional.
The information on micronutrients and phytochemicals contained on this Web site does not cover all possible uses, actions, precautions, side effects, and interactions. It is not intended as medical advice for individual problems. Liability for individual actions or omissions based upon the contents of this site is expressly disclaimed.