Q. Are nuts really good for your heart?

The Harvard Men's Health Watch reports that studies show healthy men, and those who have already suffered a heart attack, can reduce cardiovascular risk by eating nuts regularly.

Here are some facts about nuts:

Ÿ Fiber. All nuts contain fiber, which helps lower your cholesterol. Fiber also makes you feel full, so you eat less.

Ÿ Some nuts contain plant sterols, a substance that can help lower your cholesterol.

Ÿ Nuts contain mono- and polyunsaturated fats known to benefit the heart.

Ÿ Many nuts are rich in omega-3 fatty acids. Omega-3s are a healthy form of fatty acids that seem to help your heart by, among other things, preventing dangerous heart rhythms that can lead to heart attacks.

Ÿ Nuts are a source of l-arginine, which is a substance that may help improve the health of your artery walls by making them more flexible and less prone to blood clots that can block blood flow.

Ÿ Vitamin E in nuts may help stop the development of plaques in your arteries, which can narrow them, leading to chest pain, coronary artery disease or a heart attack.

In addition, nuts may help lower cholesterol by simply replacing less healthy foods in your diet.

"Nuts may not be the key to cardiovascular health, but adding nuts to a balanced, healthful diet can take you one step away from heart disease," says Dr. Harvey B. Simon, editor in chief of Health Watch.

However, there isn't hard evidence for the benefits of nuts to your heart. The U.S. Food and Drug Administration (FDA) only allows food companies to say evidence suggests but does not prove that eating nuts reduces heart disease risk.

Most nuts contain at least some substances that are good for your heart. However, while nuts are loaded with nutrition, they are also high in calories; as much as 80 percent of a nut is fat. Two ounces of nuts a week appears to help lower heart disease risk, so don't eat nuts like an elephant or you will become one.

Nuts don't vary a lot in caloric content. Almonds are on the low end with 160 calories per ounce. Macadamias are on the high end with 204 calories per ounce.

Most nuts appear to be good for you. Walnuts, almonds, macadamia nuts, hazelnuts and pecans are considered very good for your heart.

Walnuts: While all nuts contain heart-healthy omega-3 fats, walnuts have high amounts of alpha linoleic acid (ALA). Research has suggested that ALA may help heart arrhythmias, and a 2006 Spanish study suggested that walnuts were as effective as olive oil at reducing inflammation and oxidation in the arteries after eating a fatty meal.

Almonds: These nuts contain more calcium than any other nut, making them a great food for overall health. They are rich in fiber and vitamin E, an antioxidant that helps fight dangerous inflammation and possibly health conditions such as lung cancer and age-related cognitive decline.

Macadamias: Although high in fat, macadamias supply good levels of the healthy monounsaturated variety. They're a rich source of fiber and contain minerals including magnesium, calcium and potassium.

Hazelnuts: These are a good source of folate, which plays a key role in keeping homocysteine within normal levels. Homocysteine is an amino acid which has been associated with heart problems as well as conditions like Parkinson's disease.

Pecans: These are packed with plant sterols. Pecans are also antioxidant-rich which helps prevent the plaque formation that causes hardening of the arteries. They're rich in oleic acid, the healthy fat found in olives and avocado. As a good source of vitamin B3, pecans help fight fatigue.

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