As well as being a great source of daily nutrients, nuts also help to prevent a number of serious diseases and health complications including heart disease, cancer and diabetes.

Heart health. Walnuts and pecans have been the nutty centerpiece of two separate Loma Linda University studies investigating the association between nut consumption and heart health. In both studies it was shown that a nut-enriched diet could dramatically reduce overall cholesterol levels, in some cases more than twice as much as a traditional cholesterol-lowering diet. The "stickiness" in the blood vessels which restricts blood flow was decreased on both nut-enriched diets, improving the elasticity of damaged artery linings and lowering the risk of heart disease by up to 25%.

The high levels of unsaturated fat in nuts is largely what helps to lower cholesterol levels, but other nutrients in nuts also play a role. For example, the protein in nuts is high in arginine, an amino acid that relaxes the blood vessels, allowing blood to flow more easily through the arteries. High levels of Vitamin E help to prevent the oxidation of cholesterol, which contributes to fatty buildup in the arteries. Folate lowers homocysteine levels in the blood (high levels of homocysteine are a strong predictor of heart disease), while calcium, magnesium, and potassium lower blood pressure.

Cancer. The high levels of unsaturated fat and plant protein in nuts that help protect against heart disease also help protect against cancer. To add to that, the amino acid arginine present in nuts has been shown to inhibit tumor growth and enhance general immunity.

The selenium in nuts is also a powerful antioxidant which protects against cancer and heart disease. Brazil nuts are possibly the best cancer-combatants due to the fact they contain around 2,500 times as much selenium as any other nut.

Walnuts and pecans also contain ellagic acid which has been shown in laboratories to inhibit the growth of tumors caused by certain carcinogens. Ellagic acid is currently used as an alternative and complementary medicine in the treatment of cancer.

Many researchers also believe that vitamin E helps to protect against some cancers. Nuts - and almonds in particular - are an excellent source of this potential cancer-combating vitamin. A 1 oz handful of almonds provides one-third of the recommended daily intake for vitamin E.

Diabetes. Results from a comprehensive Harvard study of 83,000 women over 14 years showed that women who regularly consumed at least 1 oz of nuts per week were almost 20% less likely than women who rarely ate nuts to develop Type 2 diabetes. Similar results were found for women who ate peanut butter five times a week. However, researchers also noted that participants who included nuts or peanut butter in their diets also had healthier diets overall, eating less meat, less trans fat and fewer highly-refined grain foods. They also smoked less and exercised more than non-nut-eaters. These lifestyle factors dramatically reduce the risk of Type 2 diabetes in both men and women.

Nuts can also help in the treatment of diabetes. A 1999 study of vegetarian diets showed that vegetarian foods, including nuts, lead to improved control of blood glucose, lower insulin requirements and better weight control for people with diabetes.