amino acids

What Is It?
Health Benefits

Dosage Information

Guidelines for Use

General Interaction

Possible Side Effects



Evidence Based Rating Scale 

What Is It?

The body uses chemical substances called Amino acids to build the exact type of Protein it needs to perform a host of bodily functions There are two types of amino acids: essential and nonessential. While the body must get the essential amino acids from foods, it can manufacture the nonessential amino acids on its own if it has the necessary components.

Of the approximately 80 amino acids found in nature, only 20 are necessary for proper human growth and function. Not only do they help make neurotransmitters--the chemicals that convey messages in the brain--they also help produce: hormones such as insulin; enzymes that activate bodily functions. In addition, they are essential for the repair and maintenance of organs, glands, muscles, tendons, ligaments, skin, hair, and nails.

An amino acid deficiency is usually caused by a diet that is low in protein, although the level of certain acids can also drop in the presence of trauma, infection, medication effects, stress, aging, and chemical imbalances within the body. A specific type of blood test can detect deficiencies, which can be corrected by taking amino acid supplements.

Health Benefits

Certain amino acids taken in supplement form may aid in fighting heart disease, lowering blood pressure, protecting against stroke, and alleviating intermittent claudication (a type of leg pain caused by restricted blood flow through arteries in the legs). They may also help in treating cancer, reducing sugar cravings, building immunity, and protecting the body in various other ways.

Specifically, amino acids may help to:

Protect the heart. Several amino acids are being studied for their role in keeping the body's biggest muscle -- the heart -- in tip-top shape. L-arginine is one of the best-known supplements used to treat cardiovascular disease, due to its potential vasodilating effects (helping to open-up blood vessel passages and improve blood flow to the heart). The heart is also highly dependent on L-carnitine, which transports fatty acids to the mitochondria, or "factory" portion of cells, which then convert fat into energy that the heart can use.

Researchers are exploring these amino acids for their potential to help speed recovery after a heart attack, as well as to treat angina (chest pain), arrhythmia (irregular heartbeats), coronary artery disease, and congestive heart failure.

Some evidence has shown that patients with heart failure and other cardiovascular conditions seem to have decreased levels of carnitine in their heart tissue. (1, 2) Several studies indicate that taking carnitine orally after a heart attack reduces complications and mortality. (3-5) Early studies also indicate that taking these amino acids orally improves exercise tolerance in patients with chronic stable angina, and improves symptoms in patients with congestive heart failure. (6-12) However, study results have been inconsistent. In a 2000 study of patients with coronary artery disease also receiving conventional medical treatment, arginine supplementation did not improve blood vessel disease, thus may not benefit these patients. (13) In a 2010 study of 60 healthy, active participants, taking arginine prior to exercise did not affect nitric oxide nor improve physical performance. (14) More research is needed. 

Treat Parkinson's disease. By helping to nourish the cells in the brain that produce dopamine, amino acids (such as tyrosine, SAMe, and acetyl-L-carnitine) may be useful in treating Parkinson’s disease (PD). In this degenerative nervous-system disorder, nerve cells that manufacture the neurotransmitter dopamine start to die off. With insufficient dopamine to relay messages between nerve and muscle cells, it becomes progressively more difficult for the body to move in a smooth and normal way. 

L-tyrosine can be converted into L-dopa, the immediate precursor to dopamine and active ingredient in levodopa, the mainstay drug for PD. Both Parkinson's disease and L-dopa are associated with depleting the body's tyrosine levels. However, a 2011 case study found that when L-dopa is administered in proper balance with the amino acids tyrosine, cysteine, glutathione and SAMe, as well as 5-HTP, a derivative of the amino acid tryptophan, any side effects of L-dopa become controllable or do not occur at all, making the levodopa treatment more effective in relieving symptoms of PD. (15) More research is needed. 

Some evidence suggests that taking creatine may help slow progression of Parkinson's disease in patients in with early stage disease who do not need to take medications to control symptoms. In a 2006 study of 200 patients who had been diagnosed with PD within the previous five years, taking 10 g of creatine daily significantly decreased the rate of disease progression compared to placebo. (16) However, in another study, patients whose disease was more advanced did not get the same benefit, but they were able to have smaller increases in their doses of conventional medications. (17) Creatine also has been shown to increase the benefits of resistance training in patients with PD, who generally experience decreased muscle mass and strength. (18) 

Studies have shown that patients with PD are often deficient in glutathione, a compound of three amino acids--cysteine, glutamic acid, and glycine--and an important part of the body's antioxidant defense system. (19-25) Adequate glutathione levels may help to protect the brain from free-radical damage and may also increase the body's sensitivity to dopamine. A 2006 review of antioxidant use in Parkinson’s disease found only one study involving glutathione. With fewer than 30 subjects, it did show a small but statistically significant improvement in symptoms of Parkinson's disease. (26) However, a small 2009 study had conflicting results. In the study with 20 patients randomized to receive glutathione or placebo, there were no statistically significant differences between the groups on the Unified Parkinson's Disease Rating Scale. (27) Larger studies are needed to establish appropriate doses and timing of glutathione therapy.  

Limited research indicates that DLPA (D, L-phenylalanine), which contains two forms of the amino acid phenylalanine, may help to improve rigidity, walking, speech and depression associated with Parkinson's disease. (28) More research is needed. 

Prevent tumors. Taking mixed amino acids may help to slow tumor growth and to promote healing. A 2011 review showed that supplementing diets with amino acids like arginine and glutamine--the most abundant amino acid in the body--impedes tumor proliferation. However, the studies have not assessed the effects of these amino acids on tumor growth in terms of apoptosis, or programmed cell death. Results have been conflicting and inconclusive. (29)  

Glutamine may also help to diminish chemotherapy side effects, such as mouth sores. Studies have shown that using glutamine as an oral rinse, it can help reduce the incidence, severity, and duration of mouth sores induced by chemotherapy or radiation. (30-32) 

Speed healing after surgery and illness. Taking amino acids after surgery will help to ensure that the body has the raw materials needed to rebuild tissue such as skin, muscle, and internal organs. Glutamine administered after major abdominal and other surgeries, has been shown to speed healing, improve immune function and shorten hospital stay during recovery. (33-35)  

Arginine also has been shown to contribute to a faster recovery time after surgery or serious illness, including cancer. Several studies have shown that supplementing the diet of patients before or after surgery with L-arginine, RNA and eicosapentaenoic acid (EPA) reduces the number of infections, improves wound healing and shortens recovery time. (36-40) 

In a 2011 review of studies evaluating treatment tolerance in cancer patients, supplementation with glutamine was shown to increase the efficacy of cancer treatment by reducing toxicity to healthy tissue and improving outcomes. Supplementation with branched amino acids led to reduced length of hospital stay, decreased morbidity, and improved quality of life. In addition, supplementation with arginine taken before surgery led to a reduced incidence of complications and a significant increase in long-term survival. (40) 

Replenish thyroid hormone. Tyrosine is a main ingredient in thyroid hormones, which help regulate metabolism. It is a precursor of thyroxine and can boost this primary thyroid hormone level. Tyrosine can be helpful in cases where a patient with thyroid under activity is malnourished or not eating a proper diet. Otherwise, tyrosine may exacerbate hyperthyroidism, which occurs when the thyroid secretes too much hormone, thus speeding up metabolism. (41)

Relieve chronic pain. According to favorable patient evidence, DL-Phenylalanine (DLPA) may be helpful for the relief of chronic pain and may increase the effect of pain relief in patients receiving narcotics. (42) Also, 5-HTP is transformed in the brain into serotonin, a "feel good" nervous system chemical. Increasing serotonin levels may help to promote sleep, a critical issue for some patients suffering from chronic pain conditions. A review of 24 trials indicates efficacy in improving poor sleep associated with fibromyalgia. (43-44) However, research is limited. More studies are needed.


  • tablet
  • powder
  • liquid
  • capsule 

Dosage Information 

Cancer: As an oral rinse: glutamine, 1 to 4 grams (g) swished in the mouth and swallowed, 2 to 4 times daily from day one of chemotherapy for 28 days, or for four days after symptoms subside. For tumor growth: No dosage has been established; follow label directions on a mixed amino acid complex. 

Chronic pain: 5-HTP: 200 - 400 milligrams (mg) a day, in 2 or 3 divided doses has been used; DLPA: Up to 1,500 mg a day in 2 or 3 divided doses between meals have been used. 

Heart Disease Prevention: Carnitine, 500 - 1,000 mg per day has been used. 

Parkinson's Disease: 1,000 mg tyrosine; 1,000 mg methionine; 500 mg acetyl-L-carnitine; 100 mg phosphatidylserine (PS), twice a day between meals have been used. 

Surgery Strategies: Follow label directions for a mixed amino acid complex (usually 3 capsules a day); continue until 2 weeks after surgery. After surgery, 18 to 30 g of glutamine dipeptides per day has been used in a 60 to 70 kg (132 to 154 pounds) patient. Higher doses are used for severely stressed patients with multiple injuries, burns, sepsis and immune deficiency. 

Thyroid Disease: For hypothyroid: 1,000 mg L-tyrosine a day. 

Guidelines for Use 

Look for amino acid supplements prefaced by the letter L (such as L-arginine). These are more similar to the amino acids in the body than are amino acid supplements prefaced by the letter D. (One exception is D-L phenylalanine, which treats chronic pain.)

The essential amino acids are histidine, isoleucine, leucine, lysine, methionine, cysteine, phenylalanine, tyrosine, threonine, tryptophan, and valine.

The nonessential amino acids are alanine, aspartic acid, arginine, citrulline, glutamic acid, glycine, hydroxyglutamic acid, hydroxyproline, norleucine, proline, and serine.

Take amino acid supplements at least a half-hour before or after a meal; taking them when the stomach is empty eliminates the possibility that they will compete with the amino acids in high-protein foods. The only exception to this is glutathione (a combination of glutamic acid, cysteine, and glycine), which should be taken with food to prevent stomach irritation.

General Interaction

There are no known drug or nutrient interactions associated with the use of amino acids.

Possible Side Effects

Avoid higher than recommended doses; certain amino acids can be toxic in excessive amounts, causing nausea, vomiting, or diarrhea.


Those who have a serious illness or are pregnant should consult a doctor before taking amino acid supplements. Those who have genital herpes or are prone to cold sores should avoid taking arginine, as it can trigger outbreaks of these disorders. 

Those who take an individual amino acid supplement for longer than one month should take it with an amino acid complex that contains a variety of amino acids to ensure a proper balance of all the amino acids. To be safe, never take individual amino acid supplements for longer than three months unless under the direction of a doctor familiar with their use. 


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Date Published: 04/18/2005

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