L-Cysteine is one of the two proteinogenic amino acids that contain a sulfur atom (the other is methionine). It is considered a nonessential amino acid because it is produced in the human body. Individuals who are deficient in cysteine, however, must be treated with supplements.
L-cysteine is found in many foods including meat, dairy products, eggs, nuts, seeds, and legumes. It is also abundant in protein powders used in weight-loss and body-building shakes and smoothies.
The amino acid may provide a variety of health benefits. In alternative medicine, L-cysteine is touted as a natural treatment for:
- Cardiovascular disease
- Chronic bronchitis
- Inflammatory bowel disease
In addition, it is said to enhance lung health in people with chronic obstructive pulmonary disease (COPD), and can also help prevent colon cancer, boost sports performance, and promote detox.
L-Cysteine, along with the amino acids glutamine and glycine, is a building block of the powerful antioxidant glutathione. The body can make cysteine from the amino acids methionine and serine, however, if these are in short supply, supplementing with L-cysteine can fill the gaps. Luxxe White Enhanced Glutathione by Frontrow International contains 120mg of L-Cysteine.
Research on the effects of L-cysteine supplementation is limited, however, the amino acid shows some benefits for certain health conditions. Here's a look at several key findings from the available research:
Research suggests that L-cysteine may aid in the treatment of diabetes by lowering blood sugar, reducing insulin resistance, and preventing blood vessel damage.
A 2012 literature review published in the Canadian Journal of Physiology and Pharmacology found that cysteine-rich whey protein improves glucose metabolism in people and animals with type 2 diabetes. However, the study authors note that more research is needed.
An earlier study published in Free Radical Biology & Medicine found diabetic rats treated with L-cysteine experienced a significant decrease in blood-sugar levels and insulin resistance. It also appeared to inhibit blood vessel inflammation, a key contributor to heart disease among diabetics. While the study was based on animals and not humans, the amino acid shows promise for those with diabetes.
A 2009 study from the Dutch journal Biochimica et Biophysica Acta suggests that L-cysteine shows promise in the treatment of colitis (a type of inflammatory bowel disease). In tests on pigs, scientists found that L-cysteine may help reduce colitis-associated inflammation of the gastrointestinal tract.
L-cysteine may help prevent exercise-induced overproduction of free radicals, a process shown to contribute to oxidative stress. In an experiment involving 10 male basketball players, the authors of a 2007 study published in Clinical Chemistry and Laboratory Medicine determined that one week of supplementation with L-cysteine helped boost antioxidant capacity and reduce free radical production.
Dosage and Preparation
L-cysteine is available as a dietary supplement in capsule and powder form. There is no standard recommended dosage amount. Follow the recommendations on the supplement label.
L-Cysteine and NAC
Are L-cysteine and NAC the same thing?
N-acetyl-L-cysteine (NAC) is similar to L-cysteine, but not exactly the same. Chemically speaking, NAC is an acetylated variant and precursor of the amino acid L-cysteine. While L-cysteine is found in many food sources, NAC is not—it is only available through supplementation. The purported health benefits of NAC are also different than the benefits of L-cysteine. NAC shows promise for treating psychological disorders, such as obsessive-compulsive disorder, addiction, and trichotillomania.