Amino Acids

What do Amino Acids do?

Amino acids are the building blocks of protein. Twenty amino acids are needed to build the various proteins used in the growth, repair, and maintenance of body tissues. Eleven of these amino acids can be made by the body itself, while the other nine (called essential amino acids) must come from the diet. The classification of an amino acid as essential or nonessential does not reflect its importance, because all twenty amino acids are necessary for health. Instead, this classification system simply reflects whether or not the body is capable of manufacturing a particular amino acid.

The essential amino acids are isoleucine, leucine, lysine, methionine, phenylalanine, threonine, tryptophan, and valine. Another amino acid, histidine, is considered semiessential because the body does not always require dietary sources for it. The nonessential amino acids are arginine, alanine, asparagine, aspartic acid, cysteine, glutamine, glutamic acid, glycine, proline, serine, and tyrosine. Other amino acids, such as carnitine, are made from the combination of other amino acids, in this case lysine and methionine.

Where are Amino Acids found?

Foods of animal origin, such as meat, fish, poultry, eggs, and dairy products, are the richest dietary sources of the essential amino acids. However, the outdated belief that vegetarians need to be concerned about combining certain foods to obtain enough essential amino acids has now been disproved by research and is almost universally rejected by scientists. Part of the reason that vegetarians do not need to “balance” amino acids is that the body’s requirement for essential amino acids now appears to be much less important than researchers once believed, especially in adults. In fact, research indicates that protein deficiencies rarely occur in people who simply eat enough calories. As a result, the old scientific term for protein deficiency, “kwashiorkor,” has been dropped from use and replaced by the term “protein-calorie malnutrition.”

Who is likely to be deficient in Amino Acids?

The vast majority of Americans eat more than enough protein and also more than enough of each essential amino acid for normal purposes. Anyone not consuming an adequate number of calories, dieters, and some strict vegetarian body builders may not consume adequate amino acids. In these cases, the body will break down the protein in muscle tissue and use those amino acids to meet the needs of more important organs or simply not build more muscle mass despite increasing exercise.

How much Amino Acid is usually taken?

Nutrition experts recommend that protein, as a source of amino acids, should account for 10–12% of the calories in a balanced diet. However, requirements for protein are affected by age, weight, state of health, and other factors. On average, a normal adult requires approximately 0.36 grams of protein per pound of body weight. Using this formula, a 140-pound person would need 50 grams (or less than 2 ounces) of protein per day. An appropriate range of protein intake for healthy adults may be as low as 45–65 grams daily. Some athletes have higher amino acids requirements. Most American adults eat about 100 grams of protein per day, or about twice what their bodies need and at least as much as any athlete requires.

Supplements of individual amino acids are recommended by nutritionally oriented doctors for specific purposes, such as lysine for herpes or phenylalanine for pain.