According to the World Health Organization, metabolic syndrome-linked to inflammation and oxidative stress that increases the risk of Type 2 diabetes and cardiovascular disease-affects 25 percent of U.S. adults and 20 percent of adults worldwide.

A nut-rich diet may offer some protection. Researchers at the University of Barcelona, in Spain, discovered that a daily one-ounce serving of mixed nuts, including raw, unpeeled walnuts, almonds and hazelnuts, boosted patients' levels of beneficial metabolites derived from metabolizing tryptophan (an amino acid), serotonin (a hormone), fatty acids and polyphenols (phytochemicals with antioxidant activity).

Their findings support the hypothesis that nuts can help prevent metabolic alterations that lead to chronic disease.