Nutrition, Metabolism, and Body Temperature Regulation

A. A nutrient is a substance in food that is used by the body to promote normal growth, maintenance, and repair. (pp. 943–944; Fig. 24.1)
1. There are six categories of nutrients: carbohydrates, lipids, proteins, vitamins, minerals, and water.
2. Essential nutrients are those that cannot be made by the body and must be obtained in the diet.
B. Carbohydrates (p. 944; Table 24.1)
1. Except for milk sugar (lactose) and small amounts of glycogen found in meats, all the carbohydrates we ingest are derived from plants.
2. Glucose is the carbohydrate molecule ultimately used by the body as fuel to make ATP.
3. The current recommendation is 125–175 grams of carbohydrates daily with the emphasis on complex carbohydrates.
C. Lipids (pp. 944–946; Table 24.1)
1. The most common dietary lipids are the neutral fats, triglycerides or triacylglycerols, which occur as saturated fats and unsaturated fats.
2. Cholesterol is another dietary lipid that is found in egg yolk, meats, and milk products.
3. Dietary fats are essential as the major source of fuel for hepatocytes and skeletal muscle, for absorption of fat-soluble vitamins, and as components of the myelin sheaths and cellular membranes of the body.
D. Proteins (pp. 946–947; Fig. 24.2; Table 24.1)
1. Animal products contain the highest-quality proteins, those with the greatest amount and best ratio of amino acids.
a. Proteins in eggs, milk, and meats are considered to be complete proteins that meet all the body’s amino acid requirements for tissue maintenance and growth.
b. Legumes, nuts, and cereals are protein-rich but not complete, but when cereal grains