Cysteine
Description
Cysteine is a sulfur-containing, semi-essential amino acid, meaning the body can produce it from methionine if enough folate and vitamin B12 are present, but it can also be obtained through diet. It is a fundamental building block for proteins and plays a critical role in various biological functions, particularly in maintaining cellular health and integrity. One of Cysteine's most significant roles is its involvement in the synthesis of glutathione, a powerful antioxidant that protects cells from oxidative stress and helps detoxify harmful substances. It is also important for the production of taurine, another amino acid, and coenzyme A. Furthermore, Cysteine contributes to healthy skin, hair, and nails due to its sulfur content, which is essential for the formation of keratin. Beyond its structural and antioxidant functions, Cysteine supports immune system health, aids in the regulation of blood sugar levels, and is involved in the metabolism of certain neurotransmitters. Its ability to act as a chelating agent also suggests a role in binding to and removing heavy metals from the body, further highlighting its importance in detoxification pathways.
Sources
Poultry (chicken, turkey)EggsBeefDairy products (milk, yogurt, cheese)Legumes (lentils, chickpeas)SoybeansSunflower seedsGarlicOnionsBroccoliBrussels sprouts
Cheapest Cysteine supplements
Best Cysteine Supplements
Value Cysteine Supplements
Optimal Dosage
Minimum500 mg
Maximum1500 mg
Safety & Toxicity
Toxicity Threshold7000 mg
Toxicity EffectCytotoxicity; nausea, vomiting, diarrhea
Interactions
Positive Interactions
Selenium
Selenium is a cofactor for glutathione peroxidase, an enzyme that works with glutathione (produced from Cysteine) to neutralize free radicals.
Folate
Folate is essential for the endogenous conversion of methionine to Cysteine in the body.
Vitamin B12
Vitamin B12 is essential for the endogenous conversion of methionine to Cysteine in the body.
Vitamin B6
Vitamin B6 is a cofactor for enzymes involved in Cysteine metabolism and its conversion to taurine.
Sulfur
Cysteine is a sulfur-containing amino acid, making its sulfur content crucial for its structure and function.
Gluthathione
Cysteine is a rate-limiting precursor for the synthesis of glutathione, enhancing the body's natural antioxidant defense.
Glutathione
Cysteine is a rate-limiting precursor for the synthesis of glutathione, enhancing the body's natural antioxidant defense.
METHIONINE
Cysteine can be synthesized in the body from methionine, making them metabolically linked.
Recommended products
Best 
L-Cysteine 500 mg
Solgar
Cysteine: 500 mg
This Solgar L-Cysteine offers a 500 mg capsule for supporting antioxidant pathways and structural proteins in the body.
Best 
L-Cysteine 500 mg
NOW
Cysteine: 500 mg
This supplement offers L-Cysteine at 500 mg, supported by Vitamin C and Vitamin B6, making it suitable for those seeking foundational amino acid and vitamin support.
Best 
Glutathione Cysteine & C
Life Extension
Cysteine: 200 mg
This product offers a synergistic blend of glutathione, its precursor cysteine, and Vitamin C, designed to support the body’s natural antioxidant defenses through multiple pathways at an economical price.
Best 
Vegan Hair Skin & Nails
NOW Solutions
Cysteine: 250 mg
A comprehensive vegan blend featuring targeted nutrients and quality mineral forms to support the health and appearance of hair, skin, and nails.
Best 
Immune Support
NaturesPlus
Cysteine: 150 mg
This NaturesPlus supplement combines key vitamins and chelated minerals with a thoughtful selection of immune-supporting herbs and compounds to offer broad daily defense.
Best 
Hair Force
KAL
Cysteine: 500 mg
KAL Hair Force offers a comprehensive blend of vitamins, minerals, amino acids, and botanicals designed to support hair, skin, and nail health, addressing multiple nutritional and structural needs.
Value 
Hair Skin & Nails
Swanson
Cysteine: 100 mg
<p>This blend offers a mix of ingredients primarily aimed at supporting hair, skin, and nail health, alongside some general wellness components, all at a cost-effective price.</p>
Best 
L-Cysteine Powder
Source Naturals
Cysteine: 900 mg
Source Naturals L-Cysteine Powder offers a flexible, higher-dose alternative for those seeking this amino acid to support antioxidant function.
Best 
L-Cysteine 500 mg
Bluebonnet
Cysteine: 500 mg
This Bluebonnet L-Cysteine offers a standard 500 mg dose in capsule form, aimed at supporting antioxidant health and structural proteins.
Budget 
Wellness D-mmunity 125 MCG
Source Naturals
Cysteine: 50 mg
This is a diverse supplement offering a wide range of vitamins, minerals, antioxidants, and unique botanical ingredients in one formula, designed to support both immune function and broader well-being.
Best 
Hair Skin & Nails
Futurebiotics
Cysteine: 150 mg
This supplement is a comprehensive blend of vitamins, minerals, amino acids, and botanicals specifically formulated to support the health and appearance of hair, skin, and nails.
Best 
L-Cysteine 500 mg
California Gold Nutrition
Cysteine: 500 mg
California Gold Nutrition offers a 500 mg L-Cysteine capsule designed to support antioxidant defenses and structural components like hair and skin.
Budget 
Free Radical Quenchers
Ecological Formulas
Cysteine: 60 mg
This supplement offers a diverse mix of antioxidants and amino acids for general cellular and overall wellness support in a convenient capsule form.
Product stats
Price per product
Average$31.18
Median$22.45
Price per serving
Average$0.62
Median$0.49
Price per 10 mg
Average$0.36
Median$0.10
Price distribution
Price per serving distribution
Price per 10 mg
Reference amount: 10 mg
Forms
Paired ingredients
Ingredient forms
L-Cysteine Hydrochloride (7) 82
L-Cysteine Hydrochloride is a hydrochloride salt of L-Cysteine, which is the biologically active form of the amino acid. It is an essential precursor for glutathione, a powerful endogenous antioxidant, and plays a vital role in protein synthesis, including keratin, which is fundamental for healthy skin, hair, and nails. This salt form enhances its stability and solubility, making it suitable for dietary supplements.
Pros
- Highly bioavailable source of L-Cysteine
- Supports endogenous glutathione production
- Potent antioxidant properties
- Aids in detoxification processes
- Contributes to healthy skin, hair, and nails
Cons
- May have a sulfurous odor or taste
- Potential for mild gastrointestinal discomfort in some individuals
Per product
Avg$13.54
Med$11.80
Per serving
Avg$0.29
Med$0.19
Per 10 mg
Avg$0.03
Med$0.03
Price distribution
L-Cysteine Hydrochloride Monohydrate (1) 82
L-Cysteine Hydrochloride Monohydrate is a hydrated hydrochloride salt of L-Cysteine. Similar to the anhydrous form, it provides L-Cysteine, a semi-essential amino acid crucial for the synthesis of glutathione, the body's master antioxidant. The monohydrate form offers comparable stability and bioavailability, facilitating its use in nutritional supplements to support detoxification, immune function, and the structural integrity of tissues like skin, hair, and nails.
Pros
- Excellent source of L-Cysteine for glutathione production
- Potent antioxidant benefits to combat free radical damage
- Supports liver detoxification pathways
- Contributes to the health and strength of hair, skin, and nails
- Good stability for formulation
Cons
- May possess a faint sulfurous smell or taste
- Some individuals might experience minor gastrointestinal upset
Per product
Avg$18.51
Med$18.51
Per serving
Avg$0.22
Med$0.22
Per 100 mg
Avg$0.02
Med$0.02
Price distribution