Functional foods are generally considered foods or beverages that provide health benefits in addition to their basic nutrients. These foods may be whole foods (e.g., fruits, vegetables) or they may be enhanced to provide a benefit (e.g., orange juice fortified with calcium).

Common health benefits associated with functional foods include reductions in the risk of cancer, cardiovascular disease, diabetes and osteoporosis. Other possible benefits include a reduced risk of macular degeneration and gastrointestinal disorders, as well as improvements in memory.

The component of functional foods that provides a specific health benefit can come from plant sources (phytochemicals) or animal sources (sometimes referred to as zoochemicals). Fiber, soy protein, certain fatty acids and probiotics are examples of food components associated with specific health benefits.

Each component acts in a specific way in the body to impart a health benefit. Some may act as antioxidants, while some may trigger enzyme activity.

In general, a high-fiber, low-fat diet rich in plant foods (including 5 to 9 servings of fruits and vegetables per day) is recommended to promote good health and help reduce the risk of a variety of diseases and medical conditions.

Health claims may be made that identify a relationship between a specific food component and risk of disease. However, these claims are subject to approval by the U.S. Food and Drug Administration (FDA). Consumers should pay careful attention to packaging claims on foods. Claims made about developing component-disease relationships, or claims about how a component affects body function (structure-function claims), are less reliable than an FDA-approved health claim. Functional foods with FDA-approved health claims include oats and fortified margarine.