Restriction of fatty foods is an effective means of reducing caloric intake and is consistent with public health goals to reduce the risk of chronic diseases. Compliance with low-fat diets is enhanced by the substitution of foods with the same organoleptic properties as fat, namely flavor, texture, and mouth-feel. Fat substitutes could replace a significant proportion of dietary fat and as such become macronutrient substitutes. The safety of these materials must be established prior to introduction into the food supply. As their use increases so will concerns about their safety. Appropriate methods of safety evaluation must be used. Traditional methods for the safety evaluation of food additives are inappropriate, since concentrations of the test materials high enough to provide a 100-fold safety factor cannot be used. An approach that recognizes the unique nature of macronutrient substitutes and includes the use of in vitro, whole-animal, and human studies and nutritional, physiological, and toxicological end points is proposed. Evaluations in humans are conducted early in this program but only when the animal data adequately support these studies. Human data will complement the animal data and may eliminate the need for some animal studies. The introduction of postmarketing surveillance will identify consumption patterns, associated adverse reactions, and potentially sensitive segments of the population and will ensure the continued safety of macronutrient substitutes. (C) 1996 Academic Press, Inc.