|See Also||Amino Acids|
L-cysteine is a non-essential amino acid which can be synthesized in the body from L-methionine and L-serine. It is conditionally essential for pre-term infants. It is an important precursor for the synthesis of proteins such as glutathione, taurine, coenzyme A, and inorganic sulfate. L-cysteine has shown some anti-inflammatory properties and is important for the protection against various toxins.
The following foods have the highest concentration of L-cysteine.
- some cereals, dairy products, eggs, meat, whole grains
The following are the primary uses for L-cysteine:
- Detoxification: L-cysteine plays an important role during acetaminophen overdose. Hepatic glutathione is essential for the liver's role in detoxification; however, during acetaminophen overdose, hepatic glutathione is depleted which is life-threatening. L-cysteine via N-acetylcysteine is the antidote as it helps to restore hepatic glutathione and to prevent liver damage.
- Osteoarthritis and rheumatoid arthritis: Due to its anti-inflammatory effects, L-cysteine has also been used to treat arthritis.
- L-cysteine is available in capsules, powder, tablets, and by injection.
- Those who supplement with L-cysteine should be sure to drink 6-8 glasses of water daily to prevent the formation of cystine renal stones. Some recommend 3-5g daily of vitamin C to aid in prevention of cystine stones.
- Another delivery form of L-cysteine is N-acetylcysteine.
- Only the RDA for adults has been established at 500mg - 1.5g/day. The recommended dosages varies based on age and health status. To determine what your specific requirements are talk to your naturopathic doctor or other trained medical professional.
- General Adverse Effects: Most common side effects reported have been gastrointestinal such as nausea. Rare cases of cystine renal stone formation have been reported.
- Children: Due to lack of long-term safety studies, supplementation should be avoided in children.
- Pregnancy and Breastfeeding: Due to lack of long-term safety studies, supplementation should be avoided in pregnant and nursing women.
- Contraindications: hypersensitivity to any component of the preparation; individuals prone to cystine renal stones.
- Precautions: L-cysteine can produce a false-positive result in the nitroprusside test for ketone bodies used in diabetes.
The following are the drug interactions associated with L-Cysteine:
- Insulin - L-cysteine may inactivate insulin.
- Monosodium Glutamate - L-cysteine may increase toxicity of monosodium glutamate (MSG) in individuals who suffer from "Chinese-restaurant syndrome". Side effects include headache, dizziness, disorientation, and burning sensation.
The following indicate the nutrient interactions with L-Cysteine:
- Hendler Sheldon S., Rorvik David (Editors). PDR for Nutritional Supplements, Medical Economics Company Inc.
- Griffith Winter H (2000) Vitamin, Herbs, Minerals & Supplements: The Complete Guide, MJF Books