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Amino acids play central roles both as building blocks of proteins and as intermediates in metabolism.
L-Arginine
L-arginine has been found to inhibit the oxidation of low-density lipoproteins (LDL) to oxidized LDL (oxLDL). The oxidation of LDL to oxLDL is believed to be a pivotal early step in atherogenesis. L-arginine may also scavenge superoxide anions and hydrogen peroxide (see above), as well as inhibit lipid peroxidation.
L-arginine has been shown to have immunomodulatory activity. For example, in human breast cancer, supplementation with this amino acid has been reported to increase the quantity and cytotoxic activity of natural killer (NK) cells and lymphokine-activated-killer (LAK) cells. L-arginine is considered an immunonutrient and is added to enteral and parenteral feedings for burn, sepsis and trauma patients. The mechanism of L-arginine's possible immunomodulating activity is not entirely clear. It may, at least in part, be again due to L-arginine's role in the production of NO. Production of NO, with consequent decrease of the cyclic AMP/cyclic GMP ratio in NK cells, would favor the production of interleukin-1, which is known to activate NK cells and may directly enhance NK cell cytotoxicity. L-arginine is also a precursor in the synthesis of the tetrapeptide tuftsin, which itself appears to have immunomodulatory activity. Tuftsin's activity appears to depend on two of the four amino acids present in its structure, L-arginine and L-proline. L-arginine also participates in the synthesis of L-proline.
L-arginine's possible activity in wound repair may be due to its precursor role in the formation of L-ornithine and, ultimately, L-proline. L-proline is a key element in collagen biosynthesis.
L-arginine shows promise in the control and prevention of cardiovascular disease (including atherosclerosis, hypertension, hyperlipidemia and angina pectoris), in the relief of some forms of male infertility and some kidney disorders and it is helpful in accelerating wound healing in some circumstances. It has demonstrated some positive immune-modulating and anticancer effects. There is preliminary evidence that it could be helpful in some men with erectile dysfunction and in some others with migraine, liver disease and primary ciliary dyskinesia. There is conflicting but mostly negative evidence related to claims that it can improve exercise performance and promote lean muscle mass.
L-Glutathione
L-Glutathione is a tri-peptide - a protein - comprised from one amino acid of glutamic acid, cysteine and glycine. Glutathione is found and manufactured in every cell in the body but is found in highest concentrations in the heart, muscle tissue and the liver. Glutathione is critical for healthy immune system function.
Glutathione is critical for the healthy maintenance of the immune system. Glutathione is a powerful antioxidant that helps maintain cellular health and helps prevent oxidative stress. Glutathione has been heavily researched, and the findings on this substance have been nothing short of amazing.
Aside from being a powerful antioxidant booster1 and system detoxifier, glutathione helps produce, protect and repair deoxyribonucleic acid - DNA. In this protective role, glutathione boosts the immune system, thereby helping to power immune response.
Glutathione levels help protect the body from oxidative stress. Thus, glutathione levels are correlated with aging and physical function. One way to drastically increase glutathione levels, aside from consuming glutathione precursors, is through the ingestion of ascorbic acid - vitamin C3 - and l-glutamine and ALA (Alpha Lipolic Acid).
Glutathione is essential for immune system function and muscle growth, and any athlete who is glutathione deficient will suffer from decreased performance6 and a lack of muscle growth.
Hard training is known to deplete glutathione levels. Thus, the hard-training athlete can benefit especially from glutathione supplementation and the enhanced recovery and muscle building results seen from its use.
Deficiencies of glutathione do not produce diseases, but low glutathione levels can accelerate the appearance of aging, can lead to functional decline and weaken the immune system.
L-Phenylalanine
L-Phenylalanine is an essential amino acid, meaning that we need it for life and our bodies can't manufacture it from other chemicals. It is found in protein-rich foods such as meat, fish, poultry, eggs, dairy products, and beans. Provided you eat enough protein, you are likely to get enough L-phenylalanine for your nutritional needs.
In the body, phenylalanine is converted into another amino acid called tyrosine. Tyrosine in turn is converted into L-dopa, norepinephrine, and epinephrine, three key neurotransmitters (chemicals that transmit signals between nerve cells). Because some antidepressants work by raising levels of norepinephrine, various forms of phenylalanine have been used to combat depression. It may also be useful in the relief of vitiligo. There is some evidence that L-phenylalanine may exacerbate tardive dyskinesia in some schizophrenic patients and in some who have used neuroleptic drugs.
L-Tyrosine
L-Tyrosine is a nonessential organic amino acid that is a building block of protein. It is an organic amino acid due to the presence of a carbon atom in its makeup.
It is a precursor of the neurotransmitter dopamine, as well as a precursor to the adrenal hormones norepinephrine and epinephrine. The body can make L-tyrosine from the amino acid phenylalanine. L-tyrosine rich foods include animal meat, wheat products, oatmeal and seafood. L-tyrosine may help athletes avoid overtraining, due to its ability to offset fatigue. Because L-tyrosine is a precursor of Dopamine, supplementing with L-tyrosine may heighten mental alertness, increase feelings of well being, and offset physical and mental fatigue.
Everyone is in need of L-tyrosine include: athletes, people trying to lose weight, and the elderly. Hard training athletes may benefit from supplementing with L-tyrosine as it helps to offset fatigue and stress associated with intense training. L-tyrosine also serves to protect the integrity of the skin. Melanin, a substance which acts to protect the skin when the epidermis has been exposed to ultraviolet light, is derived from L-tyrosine. If a shortage of melanin is present within the body [because of a lack of L-tyrosine], skin defenses will be compromised. Melanin, which is derived from L-tyrosine, chemically reacts with sunlight to form a protective shield that protects the deeper layers of skin tissue.
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