The properties of three critical elements in the human diet are discussed. In the first section, the functions of sodium in the body and in the diet are considered. The relationship between sodium and hypertension is explored, and recommendations from professional health groups on the sodium consumption are presented. In the second section, the consumption of fat and cholesterol is discussed. The body's use of dietary fat is discussed, and the distinction is clarified among saturated, monounsaturated, and polyunsaturated fatty acids. An overview is given of the connection between consumption of fats and cholesterol and coronary heart disease. Data relating fat and cholesterol to cancer are reviewed, and recommendations from professional health groups are presented. In the last section, the consumption of refined sugar and caloric sweeteners is discussed within the framework of the body's need for carbohydrates. The relationshp of sugar and dental caries, hyperactivity, and hyperkinesis is discussed. References and fact sheets are included for each of these nutrients. (JD)