| acids are the basic building blocks of protein and | | | | protein per kilogram of body weight, and |
| can be obtained in an almost endless variety of | | | | endurance athletes may need about 1.3 g/kg. |
| supplemental forms, including capsules, tablets, | | | | Undeniably, protein is a vitally important nutrient |
| bars, and powders. Some available products | | | | for general health and hundreds of specific |
| provide a food like mixture of all 20 nutritionally | | | | functions in the body. The recommended dietary |
| important amino acids, while other products focus | | | | allowance (RDA) for protein is 0.8 g/kg of body |
| on the specific characteristics of isolated amino | | | | weight for adults (0.36 g/ Ib), with growing |
| acids. The evidence for the health and | | | | children, adolescents, and both power and |
| performance benefits of isolated amino acids is | | | | endurance athletes needing slightly more. By RDA |
| mixed at best. Only in limited circumstances do | | | | standards, an adult weighing 70 kg (154 Ib) needs |
| these supplements represent a valuable approach | | | | 56 g/day (about the amount provided in 8 oz of |
| for athletes. The reader is referred to separate | | | | lean meat). |
| entries in this chapter providing scientific evidence | | | | In most cases, the scientific evidence for a |
| suggesting that an isolated amino acid supplement | | | | performance-enhancing effect of amino acids and |
| may be useful for promoting health or | | | | or protein comes from studies of using protein |
| performance (i.e., BCAAs, carnitine, glutamine, | | | | supplements to ensure adequate dietary protein |
| fi-hydroxy-fi-methylbutyrate [HMB], etc.). | | | | intake. In a limited number of examples, isolated |
| Protein (Casein, Whey, Soy, Collagen, Colostrum) | | | | amino acid supplements provide additional |
| Discussions of the value of protein supplements | | | | performance and/or health effects, such as those |
| have become increasingly complicated in the last | | | | noted for branched-chain amino acids for delaying |
| several years. The primary cause of debate is not | | | | fatigue, HMB and glutamine for inhibiting muscle |
| the question of whether athletes require greater | | | | loss, arginine for promoting blood flow, and |
| dietary protein intakes compared with their | | | | cyst-eine for increasing cellular glutathione levels. In |
| sedentary counterparts (the consensus suggests | | | | most other cases in which isolated amino acids |
| that they do) but rather the explosion in | | | | have been used as dietary supplements, |
| marketing of various forms of protein fractions | | | | however, benefits in health and performance have |
| like casein, whey, soy, colostrum, collagen, and | | | | been disappointing. |
| others. The protein debate has slowly changed | | | | Protein is one of the primary nutrients involved in |
| from "How much?" to "Which is best?" with no | | | | the growth, development, and repair of virtually all |
| shortage of opinions and isolated studies but no | | | | tissues in the body. Aside from simpiy ensuring |
| clear consensus to guide decision making. | | | | adequate dietary protein requirements, |
| The evidence is strong that protein needs are | | | | supplemental protein can also be beneficial |
| elevated by exercise training, infection, and other | | | | following strenuous exercise (by enhancing repair |
| periods of acute and chronic stress. Some of the | | | | and regeneration of damaged tissues) and as a |
| best evidence comes from studies of competitive | | | | weight loss aid (because of the low glycemic |
| athletes, in whom protein needs are nearly | | | | index and heightened sense of satiety provided |
| doubled during periods of intense training and | | | | by a protein meal compared with meals higher in |
| competition. Athletes competing in power or | | | | carbohydrates). |
| strength sports probably require about 1.6 g of | | | | |