Health Benefits of Nuts
Author: Winston Craig, MPH, PhD, RD.
Inhabitants of the Mediterranean countries, including the Middle East, have used nuts as food for millennia. Nuts come from different families and are classified as tree nuts (a one-seeded fruit in a hard shell) or peanuts (actually a member of the legume family).
Typically, Americans consume less than one oz of nuts and nut butters per day. Nuts account for only 2.5 percent of the total fat intake in the U.S. Mediterranean countries consume about twice the level of nuts consumed by Americans.
Nuts provide a number of useful nutrients. On average, one ounce of nuts provides about 4 grams of protein, 2-3 grams of dietary fiber, between 160 and 200 calories, and about 13 to 20 grams of fat. Nuts are naturally low in saturated fat with only 1-2 grams per ounce (although Brazil nuts have 5 g saturated fat), and nuts are free of cholesterol. Most nuts are rich in monounsaturated fat, and this lowers serum LDL and total cholesterol levels, without lowering the good HDL cholesterol levels. See Table 1 for the fat content of some common nuts.
Furthermore, an ounce of nuts typically contains 2-5 grams of polyunsaturated fat. Brazil nuts and walnuts are exceptions since they contain higher levels of polyunsaturated fat (7 g and 11 g per ounce, respectively). The polyunsaturated fat in the nuts will also lower blood lipid levels.
|Amount and Type of Fat in Various Nuts|
|Type of Nut||Saturated Fat (%)||Monounsat. Fat (%)||Polyunsat. Fat (%)|
Nuts also contain a number of important vitamins and minerals. On average, 1 ounce of nuts contain 170 mg potassium and 60 mg of magnesium. In addition, most nuts have substantial amounts of zinc, copper, and protective phytochemicals such as ellagic acid and flavonoids. Almonds and hazel nuts also have high levels of -tocopherol whereas pecans and walnuts are rich in -tocopherol. The tocopherols are a form of vitamin E known to prevent unwanted oxidation of LDL cholesterol.
A number of studies report that frequent nut consumption is associated with a reduced risk of coronary heart disease (CHD). In the Adventist Health Study, people who ate nuts 1-4 times a week had a 25% reduced risk of CHD while those who ate nuts five or more times a week experienced a 50% reduction in risk of CHD, compared to people who ate nuts less than once a week. The protective effect of nuts was seen after adjustment for many known risk factors for heart disease. The nuts consumed in Adventist Health Study were largely tree nuts (walnuts and almonds) with lesser amounts of peanuts. The Women's Health Study in Iowa also found an association between nut consumption and decreased risk of heart disease. The Heart Study from the University of Nevada, Reno found that frequent consumers of nuts tend to have lower body weights and are more health conscious than those not eating nuts.
Clinical trials have demonstrated the effective-ness of diets containing almonds and walnuts to lower blood cholesterol levels by 10-15 percent. The most recent feeding study, conducted at Loma Linda University, found that a diet in which 20% of the calories came from walnuts (3 oz a day) produced a 16% decrease in LDL cholesterol levels after 4 weeks compared with a similar diet not containing the nuts. Walnuts are different from most other nuts in that they contain a substantial amount of -linolenic acid (omega-3 fat). Data from the Multiple Risk Factor Intervention Trial (MRFIT) suggests that higher levels of -linolenic acid in the blood are associated with lower risk of stroke in the middle-aged men at high risk for cardiovascular disease.
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