Cystine – what it is, benefits, foods and contraindications!

Cystine is an amino acid that plays a special role in the composition of protein molecules and is also abundant in hair and skin keratin. If you want to know more about this compound, we invite you to continue reading.

Remember that this is a strictly informative article, so you should not be advised to take any medication, otherwise you should consult your trusted doctor who will determine the appropriate indications for you.

What is cystine?

Cystine is a sulfur- containing amino acid . It is part of the skin, hair, bones and connective tissue. It is composed of two molecules of cysteine ​​(another sulfur containing amino acid and is very similar), in fact, it is considered the most stable form of cysteine, although both can be converted to each other. on others, if necessary. The usual form administered is N-acetylcysteine ​​from the amino acid L-cysteine.

What is it for:

As its function is to form part of proteins, including keratin, cystine is essential for hair. When there is a lack, hair loss, lack of vigor and vitality can appear, at the same time as symptoms of nail weakness and skin aging are noted. In fact, it affects the entire connective tissue, so we can indicate that it serves for:

  • Detoxify the body.
  • Improve liver function.
  • Treat lung conditions
  • Remove mucus from the respiratory tract.
  • Increase skin regeneration.
  • Block the action of oxidants on tissues

Cystine-rich foods:

Here is the list of foods rich in Cystine:

  • Eggs
  • Pork, chicken, duck.
  • Fish like tuna , hake, monkfish.
  • Leite
  • Yogurt
  • Cow liver


Cereals like:

There are many foods rich in cystine , although some are more interesting than others. Especially if you want to improve your diet, while you increase the levels of this amino acid in the body you should eat more  broccoli  or take other foods rich in amino acids and vitamins that have nutrients similar to the composition of brewer’s yeast . You can also increase your consumption of green beans and Wheat Germ .

But in addition to doing it this way, there is also the possibility of preventing its deficiency through supplements in the form of capsules, pills or tablets. So we recommend them.

Health benefits of cystine:

1. It has antioxidant and detoxifying action:

The antioxidant activity of glutathione depends on the chemical action of the group containing sulfuric cystine, which makes its availability a critical factor for the production and effectiveness of glutathione. Therefore, cystine levels are limiting factors in the rate and amount of glutathione produced by the body.

2. Strengthens the immune system:

Playing a fundamental role in the formation and action of glutathione, it contributes to the maintenance of the defense system, inhibiting inflammation and stimulating the production of leukotrienes, substances that act in the defense exercised by macrophages, which are cells of the immune system very important in defense. against invading organisms.

A 2009 study showed that, in addition to reducing oxidative stress , cystine is able to reduce the inflammatory process in individuals with some type of disease, promoting an acceleration of healing without side effects.

3. Improves skin and hair:

Cystine is very present in alpha-keratin, the basic protein for building nails, hair and skin. Adequate supply of cysteine ​​ensures the raw material for the body to synthesize alpha-keratin in adequate amounts to maintain your health and vitality.

In addition, it, along with vitamins E and C and selenium , helps protect the skin by keeping defense genes active and preventing the harmful effects of ultraviolet rays on cellular DNA, which can lead to skin cancer .

This amino acid may also be useful in treating certain types of acne . One of them when treating acne with benzoyl peroxide causes even more inflammation, a combination of L-cysteine ​​with alpha lipoic acid reduces the redness and itchiness of pimples. The other, in the case of acne induced by high levels of testosterone, due to polycystic ovary syndrome , where cystine makes skin cells more sensitive to estrogen and less sensitive to testosterone.

As it is not the only factor that interferes with the health of the skin and connections, the important thing is to always maintain a nutrient rich in all nutrients, including proteins, minerals and vitamins.

4. Fight against osteoporosis:

Osteoporosis is a serious disease that occurs mainly in the elderly, leading to resorption of bone tissue, which leads to loss of bone density and high risk of fracture.

Cystine supplementation has proven to be useful in the treatment of osteoporosis especially in elderly women. Research has shown a decrease in the activity of osteoclasts, cells responsible for bone resorption, and an increase in collagen synthesis, minimizing two important factors in osteoporosis .

5. Helps in gaining muscle mass:

Like all amino acids, this is one of the building blocks of proteins. Muscles, on the other hand, are basically made of protein fibers. Therefore, an adequate supply of cystine also helps to gain muscle mass and strength, being widely used by athletes and fitness enthusiasts.

Cystine deficiency:

In rare cases of deficiency swelling, lethargy, skin lesions, impaired immune system and susceptibility to damage caused by toxins from the metabolism of substances by the liver and free radicals may occur.

Since cystine supplementation , either in the form of L-cysteine ​​N-acetyl-cysteine, can also carry some risks, it is important to always seek medical advice before starting treatment with this type of supplement.

Possible side effects:

The use of cystine in the diet should not reproduce adverse reactions. In the case of incorporating it into pills or any other type of nutritional supplement, it is possible to detect the following side effects:


  • L-cystine allergy.
  • Cystinos
  • Analytical blood and urine.
  • under 14 years old
  • Pregnancy
  • Breast-feeding
  • Sucrose intolerance.
  • Hypersensitivity to corn starch.

Cystinosis is a contraindication because this disease causes the accumulation of the amino acid in the body, especially in vital organs that form stones or kidney stones .

Also in the liver, pancreas and eyes can be detected in excess, with the possibility of producing abnormalities in the brain and in the functioning of white blood cells.

As cystine is a chemical form, people who are hypersensitive to the levorotatory form should avoid its consumption as they would suffer the side effects of a food allergy.

If you are going to have a blood or urine test, you should tell the doctor you are taking it. This can cause incongruous results.

Pregnant or lactating women should consult before starting to take it. There are no clinical studies with reliable data, so it is the doctor who should indicate whether or not to include it in this period.

In cases where you buy cystine in pills, you should check its composition. It is very likely that the tablets are made with sucrose. If you are allergic or suffer from any intolerance to this ingredient, you have contraindicated this commercial form. Likewise, most also include cornstarch.

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