Amino acids are the nitrogen and carbon based structures that link together to form proteins. There are 22 different amino acids. Thirteen of the amino acids can be synthesized within your body, either from other amino acids or from various protein cells reclaimed and recycled throughout your body. The other nine amino acids cannot be synthesized in your body and must be obtained in your diet. Proteins and the various amino acids that comprise proteins are used for a variety of functions that include facilitating neurotransmission, synthesizing hormones and building muscle tissue. Consult your doctor before taking any supplements.
Amino Acid Pool
Proteins from the diet and within your body are constantly being broken down into amino acids and rebuilt into structures like muscle tissue and hormones. As part of the constant state of change there is a pool of amino acids from which your body can draw at any given time as long as you are in positive nitrogen balance -- basically any time except starvation.
Amino Acid Supplements
Although certain amino acids are sold as individual supplements for a variety of ailments -- for example, lysine for herpes, tryptophan for depression -- there are no peer-reviewed studies to support the use of amino acid supplementation. In fact, when one amino acid is present far in excess of other amino acids the supplemented amino acid essentially blocks the other amino acids from being absorbed equitably. For now, the best approach to getting your amino acids appears to be consuming them in protein form. Consult your doctor first.
Protein Supplements
Athletes, particularly body builders, are known for chugging protein shakes. While isolated protein sources like powders and shakes are acceptable forms of protein, there is no evidence that you will be better able to utilize the protein than you would be able to utilize protein from your normal food intake. Additionally, there is no evidence to support better muscle development when you get your protein from shakes than when you get it from food. Ask a physician about protein shakes.
Daily Protein Requirements
On average, Americans get far more protein than they need each day. The Dietary Reference Intake for protein in adults is only 0.8 g per kilogram, which means that a 180 lb. person needs only 65 g of protein each day. For athletes and other people who regularly exercise and lift weights, the numbers are slightly higher -- 1.0 to 1.4 g per kilogram. For ultra-endurance athletes and competitive weight-lifters, protein recommendations can be as high as 2.0 g per kilogram. That means even at the very top end of protein needs, a 180 lb. person would still only need 130 g of protein each day.
References
- "Essentials of Exercise Physiology"; William McArdle, et al.; 2006
- "Krause's Food and Nutrition Therapy: 12th Edition"; L. Kathleen Mahan and Sylvia Escott-Stump; 2008
- "Nutrition For Sport and Exercise"; Marie Dunford and J. Andrew Doyle; 2007
- "Nutrition Concepts and Controversies, Volume 10"; Frances Sizer Webb, et al.; 2008
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