Amino Acids OverviewSkip to the navigation
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 essential amino acids are isoleucine, leucine, lysine, methionine, phenylalanine, threonine, tryptophan, and valine. Another amino acid, histidine, is considered semi-essential because the body does not always require dietary sources of 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 and taurine, are used by the body in ways other than protein-building and are often used therapeutically. L-Theanine is an amino acid found in tea that is said to help relieve stress. Beta-alanine has been used to prevent fatigue during exercise.
Our proprietary “Star-Rating” system was developed to help you easily understand the amount of scientific support behind each supplement in relation to a specific health condition. While there is no way to predict whether a vitamin, mineral, or herb will successfully treat or prevent associated health conditions, our unique ratings tell you how well these supplements are understood by the medical community, and whether studies have found them to be effective for other people.
For over a decade, our team has combed through thousands of research articles published in reputable journals. To help you make educated decisions, and to better understand controversial or confusing supplements, our medical experts have digested the science into these three easy-to-follow ratings. We hope this provides you with a helpful resource to make informed decisions towards your health and well-being.
3 Stars Reliable and relatively consistent scientific data showing a substantial health benefit.
2 Stars Contradictory, insufficient, or preliminary studies suggesting a health benefit or minimal health benefit.
1 Star For an herb, supported by traditional use but minimal or no scientific evidence. For a supplement, little scientific support.
This supplement has been used in connection with the following health conditions:
18 grams daily of L-ornithine-L-aspartate
As both a supplement and injection, L-ornithine-L-aspartate has been shown to significantly improve liver function, mental status, and brain function.
L-ornithine-L-aspartate (OA) is a nutritional supplement that has been investigated as a treatment for cirrhosis and hepatic encephalopathy. In a double-blind trial, participants taking 18 grams of OA for 14 days had significant improvements in liver function, mental status, and brain function.1 Similar benefits have also been demonstrated using injections of OA.2 , 3
Refer to label instructions
In double-blind research, alcoholics treated with L-tyrosine combined with DLPA (D,L-phenylalanine), L-glutamine, prescription L-tryptophan, plus a multivitamin had reduced withdrawal symptoms and decreased stress.
Kenneth Blum and researchers at the University of Texas have examined neurotransmitter deficiencies in alcoholics. Neurotransmitters are the chemicals the body makes to allow nerve cells to pass messages (of pain, touch, thought, etc.) from cell to cell. Amino acids are the precursors of these neurotransmitters. In double-blind research, a group of alcoholics were treated with 1.5 grams of D,L-phenylalanine (DLPA), 900 mg of L-tyrosine, 300 mg of L-glutamine, and 400 mg of L-tryptophan (now available only by prescription) per day, plus a multivitamin-mineral supplement.5 This nutritional supplement regimen led to a significant reduction in withdrawal symptoms and decreased stress in alcoholics compared to the effects of placebo.
Refer to label instructions
Aspartic acid is an amino acid that participates in many biochemical reactions relating to energy and protein. Research suggests that it may help reduce fatigue during exercise.
Aspartic acid is a non-essential amino acid that participates in many biochemical reactions relating to energy and protein. Preliminary, though conflicting, animal and human research suggested a role for aspartic acid (in the form of potassium and magnesium aspartate) in reducing fatigue during exercise.6 However, most studies have found aspartic acid useless in improving either athletic performance or the body’s response to exercise.7 , 8 , 9 , 10 , 11
How It Works
How to Use It
Nutrition experts recommend that protein, as a source of amino acids, 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 acid requirements.12 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.
Where to Find It
Foods of animal origin, such as meat and poultry, fish, eggs, and dairy products, are the richest dietary sources of the essential amino acids. Plant sources of protein are often deficient in one or more essential amino acids. However, these deficiencies can be overcome by consuming a wide variety of plant foods. For example, grains are low in lysine, whereas beans provide an excess of lysine. It was previously believed that, in order for vegetarians to obtain adequate amounts of protein, all of the essential amino acids had to be “balanced” at each meal. For example, a grain and a bean had to be consumed at the same meal. However, more recent research has indicated that, while consuming a proper mix of amino acids is important, it is not necessary to consume them all at the same meal.13
The vast majority of Americans eats more than enough protein and also more than enough of each essential amino acid for normal purposes. Dieters, some strict vegetarian body builders, and anyone consuming an inadequate number of calories may not be consuming adequate amounts of 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 will simply not build more muscle mass despite increasing exercise.
Interactions with Supplements, Foods, & Other Compounds
Amino acids include several different nutrients, each of which has the potential to interact with drugs. Look up the unique interactions for each and discuss the potential benefits and risks of your current medications with your doctor or pharmacist before adding amino acids:
Interactions with Medicines
Many Western diets provide more protein than the body needs, causing excess nitrogen to be excreted as urea in urine. The excess nitrogen has been linked in some studies with reduced kidney function in old age. Some, but not all studies have found that when people have impaired kidney function, restricting dietary intake of protein slows the rate of decline of kidney function.14
Excessive protein intake also can increase excretion of calcium, and some evidence has linked high-protein diets with osteoporosis,15 particularly regarding animal protein.16 On the other hand, some protein is needed for bone formation. A double-blind study showed that elderly people whose diets provided slightly less than the recommended amount of protein suffered less bone loss if they consumed an additional 20 grams of protein per day.17 A doctor can help people assess their protein intake and needs.
Amino acids include several different nutrients, each of which has the potential for side effects. Look up the unique side effects for each and discuss the potential benefits and risks with your doctor or pharmacist:
1. Stauch S, Kircheis G, Adler G, et al. Oral L-ornithine-L-aspartate therapy of chronic hepatic encephalopathy: results of a placebo-controlled double-blind study. J Hepatol 1998;28:856-64.
2. Kircheis G, Nilius R, Held C, et al. Therapeutic efficacy of L-ornithine-L-aspartate infusions in patients with cirrhosis and hepatic encephalopathy: results of a placebo-controlled, double-blind study. Hepatology 1997;25:1351-60.
3. Staedt U, Leweling H, Gladisch R, et al. Effects of ornithine aspartate on plasma ammonia and plasma amino acids in patients with cirrhosis. A double-blind, randomized study using a four-fold crossover design. J Hepatol 1993;19:424-30.
4. Ritsner MS, Miodownik C, Ratner Y, et al. L-Theanine relieves positive, activation, and anxiety symptoms in patients with schizophrenia and schizoaffective disorder: an 8-week, randomized, double-blind, placebo-controlled, 2-center study. J Clin Psychiatry 2011;72:34-42.
5. Blum K. A commentary on neurotransmitter restoration as a common mode of treatment for alcohol, cocaine and opiate abuse. Integr Psychiatr 1986;6:199-204.
6. Bucci LR. Nutrients as ergogenic aids for sports and exercise. Boca Raton, FL: CRC Press, 1993, 45-7 [review].
7. Wesson M, McNaughton L, Davies P, et al. Effects of oral administration of aspartic acid salts on the endurance capacity of trained subjects. Res Quart Exer Sport 1988;59:234-6.
8. Maughan RJ, Sadler DJ. The effects of oral administration of salts of aspartic acid on the metabolic response to prolonged exhausting exercise in man. Int J Sports Med 1983;4:119-23.
9. Hagan RD, Upton SJ, Duncan JJ, et al. Absence of effect of potassium-magnesium aspartate on physiologic responses to prolonged work in aerobically trained men. Int J Sports Med 1982;3:177-81.
10. Tuttle JL, Potteiger JA, Evans BW, et al. Effect of acute potassium-magnesium aspartate supplementation on ammonia concentrations during and after resistance training. Int J Sport Nutr 1995;5:102-9.
11. De Haan A, van Doorn JE, Westra HG. Effects of potassium + magnesium aspartate on muscle metabolism and force development during short intensive static exercise. Int J Sports Med 1985;6:44-9.
12. Lemon PW. Is increased dietary protein necessary or beneficial for individuals with a physically active lifestyle? Nutr Rev 1996;54:S169-75 [review].
13. Young VR, Pellett PL. Plant proteins in relation to human protein and amino acid nutrition. Am J Clin Nutr 1994;59(suppl):1203S-12S.
14. Sitprija V, Suvanpha R. Low protein diet and chronic renal failure in Buddhist monks. BMJ 1983;287:469-71.
15. Heaney R. Protein intake and the calcium economy. J Am Diet Assoc 1993;93:1259-60 [review].
16. Abelow BJ, Holford TR, Insogna KL. Cross-cultural association between dietary animal protein and hip fracture: a hypothesis. Calcif Tiss Int 1992;50:14-8.
17. Schürch MA, Rizzoli R, Slosman D, et al. Protein supplements increase serum insulin-like growth factor-I levels and attenuate proximal femur bone loss in patients with recent hip fracture. A randomized, double blind, placebo-controlled trial. Ann Intern Med 1998;128:801-9.
Last Review: 10-14-2014
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The information presented in Aisle7 is for informational purposes only. It is based on scientific studies (human, animal, or in vitro), clinical experience, or traditional usage as cited in each article. The results reported may not necessarily occur in all individuals. For many of the conditions discussed, treatment with prescription or over the counter medication is also available. Consult your doctor, practitioner, and/or pharmacist for any health problem and before using any supplements or before making any changes in prescribed medications. Information expires June 2015.