Nutrition: Overview

Nutrients are the constituents of food necessary to sustain the normal functions of the body. All energy (calories) is provided by three classes of nutrients: fats, carbohydrates, and protein (Fig. 1). Because the intake of these energy-rich molecules is larger (g amounts) than that of the other dietary nutrients, they are called macronutrients. This chapter focuses on the kinds and amounts of macronutrients that are needed to maintain optimal health and prevent chronic disease. Those nutrients needed in lesser amounts (mg or μg), vitamins and minerals, are called micronutrients .

Figure .1 : Essential nutrients obtained from the diet. [Note: Ethanol may provide a significant contribution to the daily caloric intake of some individuals.]