In addition to omega-3s, fish is high in protein, vitamins, and minerals. And, it's low in saturated fat.

Hundreds of studies suggest that omega-3s may provide some benefits to a wide range of diseases: cancer, asthma, depression, cardiovascular disease, ADHD, and autoimmune diseases, such as rheumatoid arthritis.

How could fatty acids be so beneficial for so many different conditions?

"All these diseases have a common genesis in inflammation," says Joseph C. Maroon, MD, professor and vice chairman of the department of neurological surgery at the University of Pittsburgh School of Medicine. Co-author of Fish Oil: The Natural Anti-Inflammatory, Maroon says that in large enough amounts omega-3's reduce the inflammatory process that leads to many chronic conditions.

For these and other reasons, the Department of Health and Human Services (HHS), the U.S. Department of Agriculture (USDA), the American Heart Association, and the American Dietetic Association recommend eating two 8-ounce servings of fish each week.