L-cysteine is used therapeutically and nutritionally to improve the health of humans. It’s a basic building block of glutathione, which has been coined “the mother of all antioxidants.” L-cysteine supplementation, also known as N-acetyl-L-cysteine (NAC), is valued for its ability to increase glutathione levels in the body, which is extremely important for lung function, brain function and liver detoxification. Because a number of health conditions deplete your glutathione levels, you need L-cysteine to make more within your brain and body tissues.
L-cysteine is also valued for its ability to break up mucus, thereby making it easier to cough up phlegm that’s caused by respiratory and pulmonary conditions. Plus, L-cysteine is involved in regulating glutamate levels, influencing the neurons in the central nervous system. (1)
In a nutshell, we all need enough L-cysteine in order to properly fight oxidative stress and conditions affecting the brain and lungs. L-cysteine is made in small amounts by the human body, and you can also get L-cysteine from high-protein foods and supplementation.