Cystine is an oxidized dimer form of amino acid cysteine with formula (SCH2CH(NH2)CO2H)2. Cystine is a white solid which is slightly soluble in water. It provides two biological functions: a site of redox reactions and mechanical linkage which allows protein for retaining their three-dimensional structure. It is associated dimeric nonessential amino acid assembled by oxidation of cysteine. Two molecules of Cysteine are combined together by disulfide bridge for forming cysteine.

It is a sulfur containing derivative attained from oxidation of cysteine amino acid thiol side chains. It acts as an antioxidant and prevents tissues against pollution and radiation and slowing down aging process. It assist protein synthesis. It is abundant in various protein of skeletal tissues and skin or found in insulin or digestive enzymes chromotrypsinogen A, trypsinogen and papain. It is a preferred form cysteine for glutathione synthesis in cells engaged in immune system. Neurons and Lymphocytes uses cysteine for glutathione production. Optimization of glutathione levels in macrophases or astrocytes having cysteine allow cells for providing cysteine to lymphocytes and neurons associated upon demand.

Food Sources of Cystine

Food name	Weight (g)	Cystine (g)
Turkey	863	2
Soybeans	186	1
Winged beans	182	0.992
Lupins	180	0.803
Spirulina	112	0.741
Sesame seed	150	0.660
Couscous	173	0.623
Semolina	167	0.598
Hyacinth beans	210	0.586
Kielbasa	370	0.585
Butternuts	120	0.581
Black walnuts	125	0.578
Spelt	174	0.574
Durum wheat	192	0.549
Oat bran	94	0.541
Mungo beans	207	0.484
Peanuts	143	0.475
Lima beans	202	0.461
Yardlong beans	167	0.449
Millet	200	0.424

Health Benefits of Cysteine

Here are health benefits discussed about Cysteine:

Antioxidant activity

L-cysteine acts as a scavenger of free radicals which cause cellular damage through oxidative stress and promotes antioxidant capacity through glutathione preservation. It is the well-known benefit of L-cysteine which slows down aging process and prevents serious health conditions. It enhances level of glutathione and supports immune function. Research shows that immunological functions are related with deficiency of cysteine and glutathione that could be enhanced significantly and restored by supplementation of L-cysteine. Studies including HIV patients show ability of L-cysteine to enhance immune system. Study shows that formulation comprises of NAC, omega-3 fatty acids, bovine colostrum and combination of minerals and vitamins reduced decline of immune cells. Other study shows that restoring glutathione levels, L-cysteine appear have beneficial impact on immune function of people with HIV. Supplementation of L-cysteine improves immune function in postmenopausal women. Research shows that NAC supply for 2-4 months results prolonged strengthening of immune in postmenopausal women by lowering probability of immune system associated diseases as they ages.

Detoxifies body

L-cysteine prevents side effects which are caused by drug reactions or toxic chemicals. Cysteine has a pivotal role in detoxifying body. Toxic metals contain pre-oxidative effects and they diminish glutathione levels so supplementation of L-cysteine helps to restore levels which help to detoxify toxins. Doctors give NAC to people with acetaminophen overdose for preventing liver or kidney damage. Drug prompt acute liver failure is a fatal disease which is caused by toxic metabolite N-acetyl-p-benzoquinone-imine which results depletion of glutathione. Overdose patients when treated with NAC allow significant growth in glutathione activity.

Enhance male fertility

Supplementation of L-cysteine helps to alleviate depletion of glutathione during oxidative stress and is effective for treating infertility in men with poor semen quality, oxidative stress and DNA damage. Study shows that NAC acts as an effective treatment for male infertility from clinical varicocele when veins become enlarged inside scrotum. Study results shows that concentration of sperm seemed to be improved by using NAC.

Balance blood sugar level

L-cysteine is helpful to support natural ability of the body in managing and regulating normal level of blood sugar. Animal study shows that supplementation of L-cysteine reduces glycemia and markers of vascular inflammation in diabetic patients. Supplementation of L-cysteine lowers blood levels of glucose or insulin resistance significantly. There is also a reduction in plasma protein oxidation levels in rats medicated with L-cysteine.

L-cysteine promotes digestive capacity of the body due to its ability of slowing aging process. As people ages, digestive problems such as gastroenteritis and low stomach acid becomes important. It could be due to the existence of free radicals in the body. Study shows that supplementation of L-cysteine helps to lower symptoms of ulcerative colitis which is an inflammatory bowel disease which cause inflammation and sores in digestive tract that lasts for long. Research concluded that mesalamine and NAC improved symptoms of ulcerative colitis due to low chemokines which attract white blood cells and forms free radicals. NAC is safe and well-tolerated.

Respiratory health

NAC acts as an expectorant which break down mucus in the body. It lowers frequency and severity of wheezing or respiratory attacks by enhancing glutathione and thinning mucus which builds up in bronchial tubes. It is found to be helpful for those suffering allergy symptoms or having respiratory condition such as chronic obstructive pulmonary disease and bronchitis. Research shows that supplementation of L-cysteine helps to lower the burden of oxidant and inflammation found in COPD patients which is a condition involving an abnormal inflammatory response in lungs and restricted airflow which makes difficulty in breathing. NAC is used to lower COPD symptoms, exacerbations or hasten decline of lung functions.

Treat psychiatric problems

Research has shown use of NAC for treating psychiatric illnesses. Review shows that various disorders are benefited with NAC having restricted options and suboptimal outcomes having current treatments. Study shows that NAC is able to treat for addiction including nicotine addiction, marijuana dependence, pathological gambling and cocaine addiction. Report shows use of NAC to lower symptoms of obsessive compulsive disorder by promoting control of compulsive washing or obsessional triggers in patients. Study found NAC to be useful for patients with bipolar disorder and schizophrenia. It is because of antioxidant activity of NAC, as suggested by growing body of literature, psychiatric disorders are due in oxidative stress or disfunction of glutamate metabolism. Glutamate is a crucial transmitter for normal function of brain but glutamate in excess results toxic damage to brain. L-cysteine helps to adjust levels of glutamate by preventing and treating brain disorders such as schizophrenia. Study shows that L-cysteine helps to prevent and treat angina, acne, emphysema, asthma, lung cancer and colon cancer.