At the most elemental level, we eat to supply our bodies with the nutrients necessary to maintain life. So by definition, food has a rather important function. However, the term functional food refers to processed foods and drinks that are marketed as having “health-promoting or wellness-maintaining properties”. The labels on such foods often include messages such as heart healthy, helps reduce cholesterol, clinically shown to improve kids attentiveness, helps support your immune system or your digestive system or your nervous system, etc.

Geographic reference: United States
Year: 2009
Market size: $37.3 billion
Source: Singer, Natasha, “Food With Benefits, or So They Say,” The New York Times, May 15, 2011, page B1, available online here.
Original source: Nutritional Business Journal