Nuts are nutrient-dense foods that are high in fat, but the fat consists generally of unsaturated fatty acids which promote good health. Nuts also have protein, a moderate amount of carbohydrates, vitamins, antioxidants and minerals like calcium, iron, magnesium and potassium.
Tree nuts, like pecans and English walnuts, have from 9 to 15 percent protein and 65 to 72 percent fat. Peanuts, which are really legumes, have 25 percent protein and 49 percent fat. Nuts also have many bioactive substances, such as phenolic antioxidants and phytosterols. Many studies have concluded that eating nuts has beneficial effects on coronary heart disease and blood cholesterol. In 2003, the Food and Drug Administration (FDA) concluded that consumption of 43 g (1.5 oz) of nuts per day, as part of a low-fat diet, "may reduce the risk of heart disease." A study of persons at high risk of cardiovascular disease following a Mediterranean diet found a significant reduction in major cardiovascular events in the participants that were assigned to supplement their meals with walnuts, hazelnuts or almonds.
Twenty Percent Lower Death Rate
A study of food-frequency that included 76,464 women from the Nurses' Health Study (NHS) and 42,498 men from the Health Professionals Follow-up Study (HPFS) found a significant, dose-dependent inverse association between nut consumption and total mortality. The 118,962 participants in the study had never had cancer, heart disease or stroke. Over a span of approximately 30 years, 27,429 of them died. As compared with participants who did not eat nuts, those who consumed nuts seven or more times per week had a 20% lower death rate. According to the researchers, "Inverse associations were observed for most major causes of death, including heart disease, cancer, and respiratory diseases. Results were similar for peanuts and tree nuts, and the inverse association persisted across all subgroups."
Several other smaller studies have also shown that consumption of nuts five or more times per week was associated with reduced total mortality among whites, blacks and elderly persons, as compared with nut consumption less than once per week.
The studies have not indicated which component of the nuts is responsible for the reduced mortality, but the following table shows that most nuts, except Macadamia nuts, have have a significant amount of linoleic acid, which is an omega-6 fatty acid.
|Oil or Fat||Unsat./Sat.
|Brazil nut oil||2.9||-||-||14||9||37||31||-|
Avoid nut butters with hydrogenated fats
Although nuts are a good food choice, some brands of peanut butter or other nut butters use hydrogenated fats that may be harmful. Learn more about hydrogenated fats.
In some persons, the body's immune system overreacts to proteins in tree nuts or peanuts. The nut allergy symptoms can range from a minor irritation to a potentially fatal allergic reaction (anaphylaxis). It is estimated that approximately 0.4 to 0.6% of the population of the United States has a hypersensitivity reaction to dietary substances from peanuts. Allergies to nuts are usually treated by excluding them from the diet and by avoiding foods that may contain trace particles or oils from the nuts. Persons with allergies must read carefully the food labels.
Note on Brazil Nuts
Brazil nuts are high in selenium content relative to other human foods. The Required Daily Allowance (RDA) for selenium is 70 micrograms (mcg), and the tolerable upper level is 400 mcg/day for adults. The limits between the dietary requirements and toxicity for selenium are narrow. Brazil nuts have an average selenium content of 14.7 ppm with a range of 0.2 to 253. The amount of selenium in the nuts depends on the selenium content of the soil where the trees grow. Some Brazil nuts have almost no selenium, whereas others have very high amounts. It is very difficult to regulate the amount of selenium in the diet by eating Brazil nuts. Two Brazil nuts weigh about 10 grams, so two Brazil nuts with the average concentration of 14.7 ppm contain 147 mcg of selenium. However, two Brazil nuts containing 253 ppm of selenium will contain 2,530 mcg or 2.5 mg of selenium. This is substantially in excess of the tolerable upper level and already in the toxic range. It is important not to overeat Brazil nuts.