All About Amino Acids

Published: 13th April 2008
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Amino acids occur naturally in the body. They're nitrogen-containing compounds which compose the structure of proteins and are said to be essential in maintaining a healthy metabolism. When analyzed separately, it appears that each individual amino acid may have a specialized function, but insufficient scientific evidence exists to prove that any one amino acid can do its job without the help of others.

As a group, amino acids may be involved in chemical reactions in the body which:

• Promote tissue growth and repair

• Regulate mood

• Protect nerves and aid nervous system function

• Grow and maintain healthy bones and skeletal function

• Synthesize the protein needed for muscle growth

• Blunt catabolism

• Help keep skin smooth, moist and healthy

• Maintain healthy brain tissue and function

Although much in the literature refers to 28, 26, 24 and or 23 different amino acid types in the body, 20 are presumed to be the main constituents of protein. Eight of the 20 are considered "essential" to good health and must be obtained through dietary food sources or supplementation. Three of the eight are considered Branched-Chain Amino Acids (BCAAs) being studied for their potential in reducing muscle catabolism and body fat, and in building immune system strength and brain power.*

*Statement not evaluated by the FDA.

Eight essential amino acids

1) Tryptophan is the amino acid that makes you sleepy after eating turkey. Tryptophan impacts serotonin levels in the brain, affecting mood, cravings and your propensity to addiction. Tryptophan also aids the synthesis of melatonin and, hence, may affect sleep cycles.

2) Lysine research suggests that this amino acid may positively impact inflammation and strengthen bones and joints, among other benefits. At the time of this writing, medical studies indicated that lysine may aid osteoporosis and herpes.*

3) Methionine aids in the breakdown of fats and assists the digestive tract in eliminating excess heavy metals from the body. Methionine is found in many body-cleansing formulas and supplements, as it can be converted to cysteine, a precursor to glutathione (a tripeptide that plays a role in nutrient metabolism, the regulation of cellular events and is of prime importance in detoxifying the liver).

4) Phenylalanine is an amino acid that adversely affects persons with PKU (Phenylketonuria) and one that comprises roughly 50 percent of the artificial sweetener aspartame. Many nutritionists claim that, when isolated as a nutrient and consumed outside of a balanced amino acid regimen, phenylalanine can do more harm than good. Phenylalanine is a precursor to brain chemicals norepinephrine and dopamine, both of which are linked to behavior and the propensity for addiction. It's advisable to consult a physician regarding the impact of this amino acid on individual health prior to taking.

5) Threonine is said to assist in the production of collagen and elastin. Threonine may strengthen the immune system by encouraging the production of antibodies and T-cells and by promoting thymus growth and activity.

6) Valine is one of three Branched-Chain Amino Acids (BCAAs) used by the body as energy for muscle. It aids in muscle growth and recovery and helps balance nitrogen in the body. As a BCAA, valine is said to work in concert with leucine and isoleucine to blunt levels of cortisol in the body, a hormone responsible for muscle catabolism.

7) Leucine is a BCAA that helps to regulate blood sugar and grow and repair muscle tissue. Leucine helps muscles recover from injury and trauma and plays a part in regulating energy in the body. Leucine may help to prevent muscle catabolism as well.*

8) Isoleucine is a BCAA involved in blood clotting and the formation of hemoglobin (a protein in red blood cells that transports oxygen).* Isoleucine assists with regulating blood sugar and energy levels in the body.

*Statement not evaluated by FDA.

Important non-essential amino acids

Of the twelve "non-essential" amino acids, three have gained popular attention, primarily because amino research is nascent and the importance of non-essential amino acids in the diet continues to be explored.

• Glycine helps transport oxygen for cell-making. Glycine plays a key role in hormone production and immune system strength.

• Glutamic acid is said to aid mental sharpness, speed healing and combat fatigue.

• Serine produces antibodies for the immune system and shields nerve fibers. Serine provides glucose storage for the liver and muscles.

The remaining nine, non-essential amino acids are all manufactured by the body under healthy conditions and include alanine, arginine, asparagine, aspartic acid, cysteine, glutamine, histidine, proline and tyrosine.

Sources of amino acids

Every living plant and animal is said to contain amino acids, but in various types and amounts. Animal sources of amino acids include dairy, red meat, fish and poultry, and vegetable sources of amino acids include nuts, grains, beans, peas and soy - essentially wherever vegetable protein occurs. Amino acid supplementation has gained substantial recognition by nutritionists and dietary supplement companies in recent years, but amino acid supplementation benefits remain relatively unsubstantiated.

Most nutritionists and dietitians agree that most people consume adequate amounts of amino acids through a balanced diet. However, medically compromised individuals and those who don't eat enough protein may be at risk of deficiency.

Amino acid benefits and claims

Amino acid supplements for fitness training, weight loss and certain chronic psychological and physiological disorders have been aggressively promoted and sold in the U.S. despite the lack of clinical evidence to support their efficacy and health claims.

• Claims by dietary supplement companies that amino acid supplementation may enhance the muscle strength and size of bodybuilders and improve the endurance of runners and other athletes remain unsubstantiated.

• Supplement companies claim that because amino acids are crucial in the formation of nitric oxide (NO) in the body - and NO increases blood flow - more nutrients are delivered to muscles, making them grow. Critics say, however, that this growth may be temporary and simply a result of heightened water retention by muscles.

• The holistic use of amino acids to stabilize mood disorders, ease allergy symptoms, reduce the chance of heart and gastrointestinal problems, balance cholesterol and blood sugar, help with muscle weakness and fatigue, aid sleep and attention disorders and improve cognitive function are without scientific merit at this time.

Amino acid side effects and safety

Amino acid supplementation is a relatively new concept - no reports yet of adverse effects, toxicity, overdose or interactions with drugs, nutritional supplements, food or herbs. Notwithstanding, this could change in the near future as the medical community continues to isolate amino acids and explore their use in pharmaceuticals. Long-term effects of amino acid supplementation are not yet evident.


Creatine is essentially a combination of the amino acids arginine, glycine and methionine and is produced by the pancreas, kidneys and liver in small amounts. Creatine monohydrate has become one of the most popular bodybuilding supplements on the market because loosely knit scientific studies and aggressive marketing tactics have been enough to convince the athletic world that creatine supplementation can enable the extraordinary thrusts of energy beneficial to weightlifters, sprinters and other athletes.

• Because the body's natural supply of creatine is depleted so quickly during intense exercise, dietitians and nutritionists continue to theorize that creatine supplementation is a way to enhance athletic performance.

• Despite the faith of millions that creatine is an effective bodybuilding supplement which can improve muscle tone and strength and enhance endurance levels, science has yet to substantiate creatine claims of efficacy.

Amino acids efficacy and the FDA

Because amino acids are naturally occurring substances in humans, plants and animals, amino acid supplements are not inspected by the U.S. Food and Drug Administration. As a result, their safety, strength and consistency may be compromised. Although science has proven that both essential and non-essential amino acids are needed for proper body function, scientific evidence regarding the effectiveness of amino acid supplementation is scant.

For more information on Amino Acids, visit


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2. Branched-Chain Amino Acids (L-Leucine, L-Isoleucine, L-Valine). PDR for Nutritional Supplements. Sheldon Saul Hendler, PhD, MD and David Rorvik, MS, Chief Editors. Montvale, NJ: Medical Economics Company, Inc., A Thomson Healthcare Company, 2001.

3. Whey Proteins. PDR for Nutritional Supplements. Sheldon Saul Hendler, PhD, MD and David Rorvik, MS, Chief Editors. Montvale, NJ: Medical Economics Company, Inc., A Thomson Healthcare Company, 2001.

4. Chain reaction. Tabatha Elliott. Joe Weider's Muscle & Fitness. April 2007 v68 i4 p235(3).

5. Food for thought: minerals and amino acids: getting enough of these essential nutrients may help you avoid symptoms such as confusion, depression, and memory loss. Mind, Mood & Memory. Nov 2006 v2 i11 p1(2).

6. Amino acids for skin and joint care. Ann Marie Swan. Functional Foods and Neutraceuticals. July 2006 p52.

7. Amino action: no matter how much protein you eat, supplementing with amino acids could help your body work better. Jordana Brown. Better Nutrition. June 2006 v68 i6 p18(3).

8. Maternal undernutrition linked to reduced amino acids and polyamines. Women's Health Weekly. Nov 11, 2004 p136.

9. Better Nutrition's amino acids guide. Better Nutrition. Oct 2004 v66 i10 p54(2).

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