Nuts are tree seeds that form inside a hard outer shell, which is actually the fruit of the tree. Peanuts are not true nuts, but part of the legume family. All tree nuts are healthy, but almonds top the list, with Brazil nuts being the least healthy. A weakness common to all nuts is that they are not low-calorie. Almonds, cashews and pistachios are lowest at 160 calories in a 1-oz. serving, while macadamias and pecans are highest at 200 calories.
Protein
Because nuts are good sources of protein, the U.S. Department of Agriculture counts them as part of the meat food group. A 1-oz. serving of almonds or pistachios each has 6 g. Walnuts, cashews, hazelnuts, pine nuts and Brazil nuts each have 4 g; pecans at 3 g and macadamias at 2 g contain the least amount of protein. Protein in nuts is incomplete, meaning it does not contain all essential amino acids, but when combined with other food from plant sources makes a complete protein.
Fat
The fat in nuts accounts for their high calorie count, but nuts are low in saturated fat. Almonds have the least -- 1 g of saturated fat out of 14 g total in a 1-oz. serving. Pistachios are nearly as good, with only 1.5 g in 13 total. The worst offenders are Brazil nuts with 4 g saturated fat out of 19 g total, and macadamias with 3.5 g saturated out of 22 g total.
The remaining varieties fall in the middle. Hazelnuts at 17 g total, walnuts at 18 g and pine nuts at 20 g each have only 1.5 g of saturated fat. Cashews have 13 g total, with 3 g saturated. Pecans contain 20 g total, but their saturated fat is lower at 2 g.
Fiber, Vitamins and Minerals
Almonds contain the most fiber at 4 g in a 1-oz. serving; cashews and pine nuts contain the least at 1 g. Almonds excel in vitamin E content, containing one-third of the dietary reference intake for a 2,000-calorie diet. Hazelnuts are next at 20 percent, then pine nuts at 10 percent; the remaining varieties contain less than 10 percent or none. Almonds also contain 15 percent of the DRI for riboflavin, with the next closest being cashews and pine nuts at only 4 percent. All nuts are good sources of copper and manganese. Since selenium can be dangerous at high doses, limit Brazil nuts due to their high selenium content, which is 780 percent of the DRI.
Walnuts and Omega-3 Fatty Acids
Most nut varieties contain some omega-3s, but walnuts and walnut oil contain the most. The ratio of omega-6 to omega-3 should be between 2-1 and 4-1. Walnuts meet those guidelines. Omega-3s may have cardiovascular benefits. For example, a 2010 Penn State study looked at 22 adults with high LDL to see if omega-3s from plants affected blood pressure. They found adding walnuts and walnut oil to the diet lowered blood pressure both at rest and while under stress.
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