The use of N-Acetyl Cysteine (NAC) for hair growth and restoration shows some promise, but has not been clinically validated.
Human hair cells contain roughly 14% L-cysteine, which is the amino acid from which NAC is derived.
L-cysteine is capable of forming disulfide bonds, which are necessary for healthy hair to form. It may help to prevent breakage and to support long, thick strands of hair.
It has been theorized that taking N-Acetyl Cysteine may promote the healthy appearance of hair, support faster growth and even prevent or reduce hair loss.
This supplement is sometimes promoted help to naturally restore damaged hair, reverse androgenic alopecia and avoid costly hair replacement. However, there have been no research studies either demonstrating or disproving this hypothesis.



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N-Acetyl Cysteine Roles in the Body
Related Topics
L-cysteine is a semi-essential amino acid and the most important building block of glutathione – the body’s most important antioxidant.
When we consume L-cysteine from foods or when it is made in the body, a portion of this amino acid gets converted into N-Acetyl Cysteine, which can then be used to make glutathione in the liver.
Besides being a potent antioxidant substance itself, glutathione is also required for the functioning of other antioxidants, including vitamin E and vitamin C. By increasing intracellular glutathione, NAC also helps to:
- Protect DNA from incurring oxidative damage;
- Detoxify the blood of heavy metals, pesticides, antibiotics and other food chain and environmental poisons;
- Activate functions in the immune system.
All cells in the body, including hair cells, use L-cysteine to synthesize inteins. Inteins are specialized enzymes which “snip” protein chains off selectively; ensuring the proper sizes and configurations of biologically necessary protein molecules.
Further, L-cysteine is necessary for the generation of caspases which are used to dissolve dead cells; especially dead tumor cells.
N-Acetyl Cysteine for Hair
Currently, there is no definitive clinical evidence available to say that N-Acetyl Cysteine or L-cysteine supplementation for hair growth is effective. However, in numerous online reviews, there are users who say that it does help. There is also a theoretical basis for believing in this potential benefit of NAC supplements. But again, this has not yet been proven through clinical experimentation.
In one German study from 2000 involving more than 1800 human subjects, L-cysteine was shown to help to restore normal hair growth patterns when combined with Pantothenic acid (vitamin B5) and millet extract. Also, in a 2015 study it was determined that this nutrient prevents decreases in the synthesis of keratin due to iron deficiencies.
Understanding the relationship between L-cysteine and hair growth requires understanding of how keratin affects the hair. Like skin, nails, hooves and horns, hair is largely composed of keratin, a strong protein. Depending on the amounts of specific amino acids in keratin, it can be hard and unyielding (like antlers), or soft and pliable (like skin).
Cysteine’s Role in Hair Growth
Cysteine disulfide bridges in keratin chains make them difficult to dissolve.
Cysteine disulfide is capable of creating disulfide bridges which form very strong helix-shaped molecules. Individual sulfur atoms bond together and create insoluble fibrous matrices.
The amount of cysteine disulfide contained in any given keratin sample determines the pliability of the resulting substance (hair, skin, hooves, etc). Notably, it is the sulfur content in these substances which makes them distinctly odiferous, especially when burned.
Using N-Acetyl Cysteine for hair loss is based on the concept of increasing the protective layers of keratin. Thicker layers of dead keratin protect the hair as it emerges from the follicles. Supplementing the diet with L-cysteine or NAC may be beneficial at restoring proper nutritional levels and combatting the effects of dry and brittle hair.
Other nutrients like biotin, selenium, folic acid, iron, vitamins E, C and D, and water are also imperative for optimal hair growth and health.
Human hair is roughly 14% L-cysteine. L-cysteine supplements used to be manufactured in laboratories by dissolving human hair in acid. Most countries have disallowed human hair for this usage, leaving substances like poultry feathers and hog hair to be used.
Negative Effects of NAC for Hair
There is at least one potential drawback concerning using L-cysteine or N-Acetyl Cysteine for hair growth. If an excess of L-cysteine develops in the body, a deficiency of biotin may result. Deficient biotin levels are associated with increased sebum synthesis.
Sebum is the waxy/oily substance secreted by sebaceous glands in the skin which must travel through hair follicles to arrive at the surface of the scalp. Once there, sebum is used to coat the hair and keep it moist and protected. However, too much sebum can clog hair follicles, effectively suffocating the follicle and causing the hair to fall out.
Conclusions
The most prevalent cause of hair loss and poor hair health is improper dietary choices over a long period of time. Heavy consumption of empty foods that lack nutrients cause chronic imbalances in androgenic hormones; as well as in biotin, iron, sebum and other nutrients and substances.
Taking an NAC or L-cysteine supplement at home will probably not induce a marked difference in hair growth or hair health. However, it may provide a solution to one element of a larger nutritional deficiency.
By improving nutrition and by hydrating properly and remaining active, hair growth, regrowth and general health factors will all be enhanced. N-Acetyl Cysteine for hair loss and growth is likely safe and has no serious side effects at appropriate dosages.
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Article last updated on: April 15th, 2018 by Nootriment