1. Brazil Nuts

These nuts have a tender texture and a mild flavor -- and are grown on a large tree in the Amazon jungle that can get up to 160 feet tall. Brazil nuts contain protein, copper, niacin, magnesium, fiber, vitamin E and selenium. Selenium is a powerful antioxidant that works to neutralize dangerous free radicals. A study at the University of Illinois even found that the high amounts of selenium in Brazil nuts may help to prevent breast cancer.

2. Black Walnuts

The rich smoky flavor of black walnuts is much stronger than that of typical English walnuts. Their trees are native to North America, and black walnuts were a staple food to Native Americans and the early settlers. They offer many of the same nutrients as English almonds, including omega-3 fatty acids, which have been found to protect the heart, promote better cognitive function, and provide anti-inflammatory benefits for asthma, rheumatoid arthritis, eczema and psoriasis.

Walnuts also contain the antioxidant compound ellagic acid, which is known to fight cancer and support the immune system. But that's not all -- in a study in the August 2003 issue of Phytochemistry, researchers identified 16 polyphenols in walnuts, including three new tannins, with antioxidant activity so powerful they described it as "remarkable."

Walnuts are incredibly healthy for the heart. A study in the April 2004 issue of Circulation found that when walnuts were substituted for about one-third of the calories supplied by olives and other monounsaturated fats in the Mediterranean diet:

• Total cholesterol and LDL (bad) cholesterol were reduced

• The elasticity of the arteries increased by 64 percent

• Levels of vascular cell adhesion molecules, which play a major role in the development of atherosclerosis (hardening of the arteries), were reduced

3. Hazelnuts (Filberts)

Hazelnuts have a strong flavor that lends itself well to cooking and baking, which is why these nuts are often found in cookies, candies and cakes. Nonetheless, they are an incredibly nutritious source of dietary fiber, vitamin E, magnesium and B vitamins. Hazelnuts also contain phytonutrients such as arginine, an amino acid that relaxes blood vessels, and may inhibit tumor growth and boost immunity.

4. Pine Nuts

Pine nuts are technically seedlings of pinecones, not nuts, but they have a mild, nut-like flavor and provide excellent nutrition. Pine nuts are a rich source of heart-healthy monounsaturated fats, and they're full of vitamins A, C and D. Pine nuts also contain certain fatty acids that may initiate the release of an appetite-suppressing hormone called cholecystokinin (CCK).

5. Macadamia Nuts

Macadamias taste similar to hazelnuts, but with a richer, more buttery flavor. Though they're native to Australia, macadamias are grown commercially in Hawaii. These nuts are high in protein, fiber, healthy monounsaturated fats, potassium and magnesium. And, a study done at Hawaii University found that people who had added macadamia nuts to their diets for just one month had total cholesterol levels of 191, compared to 201 for those eating the typical American diet. The largest change was found in the LDL (bad) cholesterol.

6. Chestnuts

Chestnuts must be boiled or roasted before you eat them, and when you do this it brings out a sweet flavor, and their texture becomes similar to potatoes. Chestnuts are actually the lowest in fat of all nuts, and have a nutritional profile similar to brown rice. They contain as much vitamin C as lemons (by weight), lots of fiber and about one-third the calories of peanuts and cashews.