L-cysteine is an amino acid whose primary function in the body is to help build protein. Although it has reported health benefits and deficiencies are reported to cause negative effects, the substance is naturally occurring in the body, making supplements unnecessary. Some of the positive functions of l-cysteine may include building muscle mass, protecting the stomach lining to improve digestion, and acting as an antioxidant. Other reported benefits from this amino acid are counteracting acetaminophen poisoning and stimulating the immune system.
Despite its reported health benefits, many medical professionals do not believe supplementation with l-cysteine is necessary for most people who are reasonably healthy. Sometimes, people who follow vegetarian or vegan diets or others with strict dietary restrictions may get enough of it from the foods they eat. In rare cases where a deficiency exists, it can cause poor growth rates in children as well as swelling, skin lesions, and lethargy. Supplementation may also help to stimulate the immune systems of those who suffer from immunosuppressive diseases such as HIV or AIDS.
Along with other amino acids, which are often called the building blocks of protein, l-cysteine may play a role in increasing muscle mass in the body. For this reason, they are used as supplements by bodybuilders and other fitness enthusiasts who want to increase their size or strength. L-cysteine is also reported to have benefits for those who suffer from chronic lung or respiratory diseases because it helps to break down and thin mucus in the body. The amino acid may also be taken on a temporary basis when a cold, seasonal allergies, or other illness causes the body to produce more mucous.
L-cysteine is also reported to have digestive benefits, such as protecting the stomach and intestinal lining against damage from certain medications such as aspirin. It may also have antioxidant properties and has been shown to elevate the level of certain antioxidants in the body. Antioxidants are substances that break down toxins known as free radicals in the body, which are believed to play a role in the development of cancer. Some people who take l-cysteine supplements believe that it helps to stimulate the body’s natural processes for hair growth. In some cases, patients may receive l-cysteine intravenously as part of the treatment for acetaminophen overdose.