Abstract
The identification of an increasing number of substances in foods that have health-related biologic activity has opened a serious debate concerning the definition of a nutrient. Although there may be advantages to differentiating these food-borne substances as nutrients and non-nutrients, it is important to recognize that these substances have both positive and adverse effects. Moreover, the same substances may have multiple effects other than classic deficiency syndromes. In any case, it is important to differentiate the definitional needs for purposes of marketing from those required by science and health.