Amino acids

Posted on 16 July, 2020
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Amino acids are a group of nitrogen–containing organic compounds composing the building blocks of all proteins.


Amino acids are essential to human metabolism and to making the human body function properly for good health. All human proteins are made of some combination of 20 amino acids. These 20 amino acids are classified into essential and non–essential amino acids. In this context, essential means that the human body is unable to synthesize these compounds. It is essential, therefore, that they be included in one’s daily diet.

Authorities disagree to some extent as to how the 20 amino acids should be classified, at least partly because of the needs of specialized populations (such as those who have deficiency diseases such as phenylketonuria [PKU]).

The nine amino acids most commonly listed as essential are:

  • histidine
  • isoleucine
  • leucine
  • lysine
  • methionine
  • phenylalanine
  • threonine
  • tryptophan
  • valine

Up to eight other amino acids (arginine, asparagine, cysteine, glycine, glutamine, proline, serine, and tyrosine) are sometimes listed as conditionally essential because they may be essential under special circumstances. For example, arginine can be synthesized by adults, but not by children.

The non–essential amino acids that can be synthesized by the human body are:

  • alanine
  • aspartic acid
  • glutamic acid

The major source for essential amino acids in the human diet is protein from plant and animals sources. Good protein sources include dairy products, meats, fish, poultry, nuts, legumes, and eggs. Those sources are considered more complete than vegetable protein (e.g., beans, peas, and grains), which is considered a good—even if not complete—source of amino acids.

General use

Amino acids became popular as dietary supplements by the end of the twentieth century for various uses, including fitness training, weight loss, and certain chronic diseases. Some proponents of alternative treatments believe that amino acid supplements taken in the proper dosage can aid in fighting depression, allergies, heart disease, gastrointestinal problems, high cholesterol, muscle weakness, blood sugar problems, arthritis, insomnia, bipolar illness, epilepsy, chronic fatigue syndrome, autism, attention–deficit hyperactivity disorder (ADHD), and mental exhaustion.

Supplements are recommended by alternative medical practitioners for those who are not getting a proper diet, especially vegetarians who might not be getting a balance of complete protein, as well as athletes, anyone under severe stress, and anyone whose alcohol intake level is moderate to high.

Holistic practitioners believe that understanding the balance of amino acids in the body can often be the first clue to understanding why a person suffers many ailments.

Deficiencies in the proper balance of amino acids are likely to occur in those with poor diets. In addition, stress, age, infection, and lack of physical activity can also affect the levels of amino acids.

People with healthy, nutritious diets may also experience deficiencies, although this is uncommon.

Essential amino acids

The essential amino acids are those that are derived only from food and that the body cannot manufacture. They are important in many enzymatic and metabolic functions at the cellular level. In addition, although not verified by unbiased, well–controlled research studies, some holistic and alternative health practitioners feel that certain amino acids perform specific functions within the body. Examples include:

  • Tryptophan – Alternative practitioners consider tryptophan a natural relaxant that helps alleviate insomnia, treat migraines, reduce the risk of artery and heart spasms, and works with lysine to reduce cholesterol levels.
  • Lysine – Research suggests that lysine might be effective against herpes by creating a balance of nutrients that slows the growth of the herpes virus. A deficiency can result in fatigue, lack of concentration, irritability, bloodshot eyes, retarded growth, hair loss, anemia, and reproductive problems.
  • Methionine – Provides the primary source of sulfur that can prevent disorders of the hair, skin, and nails. It lowers cholesterol by increasing the liver’s production of lecithin, reduces liver fat, protects the kidneys, and promotes hair growth.
  • Phenylalanine – Serves the brain as an essential component in the production of norepinephrine, one of the chemicals responsible for transmitting the signals between the nerve cells and the brain. Phenylalanine helps people maintain alertness, reduces hunger pains, acts as an antidepressant, and improves memory.
  • Threonine – Makes up a substantial portion of the collagen, elastin, and enamel protein. It helps the digestive and intestinal tracts to function more efficiently and acts as a trigger for metabolism.
  • Valine – Promotes mental energy, helps with muscle coordination, and serves as a natural tranquilizer.
  • Leucine – Works with isoleucine to provide for the manufacture of essential biochemical processes in the body that are used for energy, thus increasing the level of stimulants in the upper brain for greater mental alertness.

Roles of certain non–essential amino acids

According to holistic practitioners, the following is a list of some of the roles of non–essential amino acids. Again, most of these roles have not been verified by rigorous scientific studies.

  • Glycine. Facilitates the release of oxygen for the cell–making process and plays a key role in themanufacturing of hormones and the health of the immune system.
  • Serine. Is important in the functioning of the central nervous system and acts with many enzymes involved in metabolic functions. It is essential in the production of antibodies for the immune system, and the synthesis of myelin, the fatty acid sheath around nerve fibers.
  • Glutamic acid is nature’s brain food because it increases mental prowess, helps speed the healing of ulcers, and aids in combating fatigue.

Alternative medicine adds amino acid supplements to a healthy diet for various purposes. The most common uses include:

  • sustaining strength in weight training to build muscles;
  • improving heart and circulatory problems or diseases, particularly in older people;
  • treating chronic fatigue syndrome;
  • treating depression and anxiety;
  • treating eating disorders, such as bulimia and/or anorexia, along with overeating;
  • increasing memory;
  • building up and sustaining the body’s immune system in fighting bacteria and viruses.

It is important to note that, while the necessity and role of all amino acids has been verified in the maintenance of optimum health, as of 2013, well–controlled, large–scale research has not provided verification of the touted benefits of such supplements over the long term.


Supplements of various amino acids are available primarily in capsule, tablet, or powder form. A common way of taking amino acids is in a multiple amino acid gel cap. These contain sources of protein from gelatin, soy, and whey. There are hundreds of supplement variations available, and in 2012, supplement sales in the United States rose seven percent from 2011 and brought in $11.5 billion. Projections estimate that by 2017, sales will reach $15.5 billion.

Side effects

Because amino acids are naturally produced substances, both in the human body and in the diet, protein supplements derived from animal, dairy, and vegetable products are not regulated by the United States Food and Drug Administration (FDA), nor are there any specified daily requirements, and they also do not show up in either drug or urine tests. Long–term effects had not been identified as of 2013.


Interactions of amino acids with drugs has not been sufficiently studied to determine yet if any adverse effects result from using amino acids with medications.

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