Cystine
A sulfur amino acid that strengthens hair and skin.
What is Cystine?
Cystine is formed from two cysteine molecules joined by a sulfur "disulfide" bond. Those bonds give structure to keratin in hair, skin and nails, and cysteine is a key ingredient in glutathione, the body's main antioxidant. It is considered conditionally essential.
Health benefits of Cystine
- Forms the disulfide bonds that strengthen hair and nails
- Supplies sulfur for keratin in skin and connective tissue
- A building block of glutathione, a major antioxidant
- Supports the body's natural detoxification
Top food sources of Cystine
See full rankingMeat, eggs, dairy, poultry, whole grains, and alliums like garlic and onion. Values shown per 100 g.
Egg, white, dried
2,102 mg
Egg, white, dried, powder, glucose reduced
2,044 mg
Egg, white, dried, flakes, glucose reduced
1,908 mg
Seeds, cottonseed flour, low fat (glandless)
1,307 mg
Seeds, cottonseed meal, partially defatted (glandless)
1,288 mg
Soy protein isolate, PROTEIN TECHNOLOGIES INTERNATIONAL, SUPRO
1,150 mg
Egg, whole, dried, stabilized, glucose reduced
1,148 mg
Soy protein isolate, PROTEIN TECHNOLOGIES INTERNATIONAL, ProPlus
1,100 mg
Egg, whole, dried
1,099 mg
Seeds, cottonseed flour, partially defatted (glandless)
1,074 mg
Soy protein isolate
1,046 mg
Soy protein isolate, potassium type
1,046 mg
How much Cystine do you need?
There is no separate Daily Value; the WHO requirement combines methionine and cysteine at about 15 mg per kg of body weight per day.
Cystine deficiency
Deficiency is rare because the body can make cysteine from methionine; very low sulfur-amino-acid intake can affect antioxidant defenses.
Nutrition data per 100 g from the USDA & FooDB databases. Daily Values follow the FDA 2016+ labeling standard for a 2,000-calorie diet. This guide is for general information and is not medical advice.
Frequently asked questions
What does Cystine do?
Cystine is formed from two cysteine molecules joined by a sulfur "disulfide" bond. Those bonds give structure to keratin in hair, skin and nails, and cysteine is a key ingredient in glutathione, the body's main antioxidant. It is considered conditionally essential.
How much Cystine do I need per day?
There is no separate Daily Value; the WHO requirement combines methionine and cysteine at about 15 mg per kg of body weight per day.
Which foods are highest in Cystine?
Per 100 g, some of the richest sources are Egg, white, dried, Egg, white, dried, powder, glucose reduced, Egg, white, dried, flakes, glucose reduced, Seeds, cottonseed flour, low fat (glandless), Seeds, cottonseed meal, partially defatted (glandless).
What happens if I don't get enough Cystine?
Deficiency is rare because the body can make cysteine from methionine; very low sulfur-amino-acid intake can affect antioxidant defenses.