Chapter 26 - Section 26.1 - Study Guide - Assess Your Learning Outcomes - Page 1024: 25

For an adult person of average size (weight and height) the protein RDA is 44-60 gram. To determine the RDA of total proteins for an individual subject, the following calculations will give good estimates 1. Multiply body weight in pounds by 0.37 OR 2. Multiply body weight in kilograms by 0.80 A weight of 130 pounds converts to 130\times 0.4535=58.9 kg Total protein RDA in grams is 130 lbs $\times$0.37 OR 58.9 $\times$ 0.80 RDA protein is 47-48 grams Sources of Proteins Humans can synthesize 12 of the 20 amino acids from organic substances when these are not contained in their diets. However, the other eight amino acids must be obtained from dietary sources because the human body cannot make them. Thus we get the concepts of complete and incomplete proteins. A food protein is a complete protein if it has all the essential amino acids. It is considered an incomplete protein if it does not contain one or more of the eight amino acids that humans cannot synthesize. These are phenylalanine, threonine, methionine, tryptophan, isoleucine, leucine, lysine, and valine. These are the essential amino acids for adults-- infants cannot make histidine, also the synthesis of cysteine, and tyrosine requires the presence of methionine phenylalanine, respectively. There are therefore 10 inessential amino acids which the adult body can make (9 in infants). Complete proteins supply all of the essential amino acids in adequate amounts for health, while incomplete proteins are missing one or more of the essential amino acids. Animal sources-- milk, meat, eggs --supply high quality complete proteins ; plant proteins are incomplete. Nevertheless, a diet too high in animal proteins can have ill effects, and plant sources of food are richer in vitamins minerals, fiber, and antioxidants .

There are conditions in which the body requires more than the normal RDA of proteins. Some of these circumstances include stress, injury, infection pregnancy and lactation. The RDA for infants and growing children is also higher than that calculated by body weight. While adequate amounts of complete proteins are essential for good health, the consumption of excessive amounts of proteins can have negative impacts on health. Fro example, excessive ingestion of proteins overworks the kidneys by overloading them with nitrogenous waste and this often results in kidney damage.