L-Cysteine

L-cysteine is a conditionally essential, sulfur bearing, amino acid present in protein.
L-cysteine is conditionally essential because it can be made in the body in sufficient quantities under normal circumstances, but it may have to be supplied from food if physical demands on the body (from physical exercise to stress) become too great.
L-cysteine performs a number of functions in the body.
L-cysteine is used to manufacture L-taurine and L-glutathione. Taurine is important because it plays a key role in central nervous system function. Taurine also helps to regulate blood pressure, helps maintain good vision and eye function, and aides in thermogenesis (fat burning) and muscle building.
Glutathione is critical for immune system function because it is a powerful antioxidant that ensures healthy cellular function and nerve signal efficiency. While direct glutathione supplementation has proven ineffective at increasing cellular glutathione levels, L-cysteine levels have proven effective for this purpose.
L-cysteine supplementation elevates NAC - N-acetyl cysteine. NAC is known to increase blood glutathione levels and preserve lean muscle mass. Therefore, the antioxidant and glutathione-elevating effects of L-cysteine are attributed to its ability to raise NAC levels.
L-cysteine is essential for T-cell production and immune system activation. L-cysteine is also a component of human hair, nails and the keratin component of skin, and is a component of the hormone insulin. L-cysteine can also be converted into glucose (for energy production) when blood glucose levels are low and this conversion may enhance athletic endurance and prevent muscle catabolism.
The gastrointestinal system may also benefit from L-cysteine. Aspirin and other drugs may stress the digestive system and stomach, and L-cysteine may protect against these side-effects by supporting a healthy stomach lining.
L-cysteine supplementation may be most effective when used in conjunction with vitamin E, vitamin C, vitamin B6 and calcium and selenium.