Final answer:
The definition of functional food excludes nonessential nutrients, which are substances the body can synthesize on its own. Functional foods are enriched with components like phytochemicals, essential nutrients, and zoonutrients that contribute to health beyond basic nutrition.
Step-by-step explanation:
The definition of a functional food includes all of the following substances except nonessential nutrients. These foods may include phytochemicals, found in whole fruits and vegetables; essential nutrients, like vitamins and minerals, which cannot be synthesized by the body in sufficient amounts; and zoonutrients , which come from animal sources and contain health-promoting compounds.
The conventional foods category of functional foods includes phytochemicals and antioxidants in whole fruits and vegetables, probiotics in yogurt and kefir, and antioxidants in dark chocolate. While vitamins and minerals are essential to human survival and considered functional components due to their role in bodily functions, nonessential nutrients do not fit the typical criteria for functional food components because the body can produce them sufficiently.