L-Cysteine: Overview, Uses, Side Effects, Precautions, Interactions, Dosing and Reviews

Overview

L-cysteine is a type of amino acid, which are the building blocks of proteins. The body makes L-cysteine from another amino acid called methionine.

L-cysteine is naturally found in foods, but because it's made in the body it doesn't need to be consumed in the diet. L-cysteine has antioxidant effects and is used to make up antioxidants such as glutathione.

People sometimes use L-cysteine for cancer, diabetes, hangover, stroke, and many other conditions, but there is no good scientific evidence to support these uses.

Don't confuse L-cysteine with N-Acetyl Cysteine (NAC). These are not the same.

Uses & Effectiveness

We currently have no information for L-Cysteine overview.

Side Effects

When taken by mouth: L-cysteine is commonly consumed in foods. But there isn't enough reliable information to know if L-cysteine is safe when used in larger amounts as medicine or what the side effects might be.

Special Precautions and Warnings

Pregnancy and breast-feeding: L-cysteine is commonly consumed in foods. But there isn't enough reliable information to know if L-cysteine is safe to use in larger amounts as medicine while pregnant or breast-feeding. Stay on the safe side and avoid use.

Surgery: L-cysteine might interfere with blood sugar control during surgery. Stop taking L-cysteine at least 2 weeks before a scheduled surgery.

Interactions

Moderate Interaction

Be cautious with this combination

Medications for diabetes (Antidiabetes drugs) interacts with L-Cysteine
L-cysteine might lower blood sugar levels. Taking L-cysteine along with diabetes medications might cause blood sugar to drop too low. Monitor your blood sugar closely.

Dosing

L-cysteine is naturally found in foods. But as medicine, there isn't enough reliable information to know what an appropriate dose of L-cysteine might be. Keep in mind that natural products are not always necessarily safe and dosages can be important. Be sure to follow relevant directions on product labels and consult a healthcare professional before using.

View References

REFERENCES:

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Eriksson CJP, Metsälä M, Möykkynen T, et al. L-cysteine containing vitamin supplement which prevents or alleviates alcohol-related hangover symptoms: Nausea, headache, stress and anxiety. Alcohol Alcohol 2020;55(6):660-666.

Syrjänen K, Eronen K, Hendolin P, et al. Slow-release L-cysteine (Acetium®) lozenge is an effective new method in smoking cessation. A randomized, double-blind, placebo-controlled intervention. Anticancer Res 2017;37(7):3639-3648.

Hellström PM, Hendolin P, Kaihovaara P, et al. Slow-release L-cysteine capsule prevents gastric mucosa exposure to carcinogenic acetaldehyde: results of a randomised single-blinded, cross-over study of Helicobacter-associated atrophic gastritis. Scand J Gastroenterol 2017;52(2):230-237.

Beltrán González AN, Vicentini F, Calvo DJ. Negative modulation of the GABAA ?1 receptor function by l-cysteine. J Neurochem. 2018;144(1):50-57.

Syrjänen K, Salminen J, Aresvuo U, et al. Elimination of cigarette smoke-derived acetaldehyde in saliva by slow-release L-cysteine lozenge is a potential new method to assist smoking cessation. A randomised, double-blind, placebo-controlled intervention. Anticancer Res 2016;36(5):2297-306.

Benson S, Scholey A, Verster JC. L-cysteine and the treatment of alcohol hangover: A commentary on Eriksson et al. (2020). Alcohol Alcohol 2021;56(5):628-629.

Clemente Plaza N, Reig García-Galbis M, Martínez-Espinosa RM. Effects of the usage of l-cysteine (l-Cys) on human health. Molecules 2018;23(3):575.

Dowlati Y, Maheux M, Meyer JH. The effect of oral L-cysteine on breast milk and plasma cysteine concentrations. Neuropsychiatr Dis Treat 2020;16:3163-3172.

McGavigan AK, O'Hara HC, Amin A, et al. L-cysteine suppresses ghrelin and reduces appetite in rodents and humans. Int J Obes (Lond) 2015;39(3):447-55.

Peana AT, Muggironi G, Fois GR, Zinellu M, Sirca D, Diana M. Effect of (L)-cysteine on acetaldehyde self-administration. Alcohol 2012;46(5):489-97.

Lee S, Han KH, Nakamura Y, et al. Dietary L-cysteine improves the antioxidative potential and lipid metabolism in rats fed a normal diet. Biosci Biotechnol Biochem 2013;77(7):1430-4.

Kim CJ, Kovacs-Nolan J, Yang C, Archbold T, Fan MZ, Mine Y. L-cysteine supplementation attenuates local inflammation and restores gut homeostasis in a porcine model of colitis. Biochim Biophys Acta 2009;1790(10):1161-9.

Tsakiris S, Parthimos T, Parthimos N, Tsakiris T, Schulpis KH. The beneficial effect of L-cysteine supplementation on DNA oxidation induced by forced training. Pharmacol Res 2006;53(4):386-90.

Hamza RZ, El-Shenawy NS. The beneficial effects of l-cysteine on brain antioxidants of rats affected by sodium valproate. Hum Exp Toxicol 2017;36(11):1212-1221.

Meduri A, Grenga PL, Scorolli L, Ceruti P, Ferreri G. Role of cysteine in corneal wound healing after photorefractive keratectomy. Ophthalmic Res. 2009;41(2):76-82.

Milani M, Colombo F; GFM-O-Trial Investigators Group: Chiara Baraldo (Padova), Mauro Barbareschi (Milano), et al. Efficacy and tolerability of an oral supplement containing amino acids, iron, selenium, and marine hydrolyzed collagen in subjects with hair loss (androgenetic alopecia, AGA or FAGA or telogen effluvium). A prospective, randomized, 3-month, controlled, assessor-blinded study. Skin Res Technol 2023;29(6):e13381.

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CONDITIONS OF USE AND IMPORTANT INFORMATION: This information is meant to supplement, not replace advice from your doctor or healthcare provider and is not meant to cover all possible uses, precautions, interactions or adverse effects. This information may not fit your specific health circumstances. Never delay or disregard seeking professional medical advice from your doctor or other qualified health care provider because of something you have read on WebMD. You should always speak with your doctor or health care professional before you start, stop, or change any prescribed part of your health care plan or treatment and to determine what course of therapy is right for you.

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