7 Important Benefits Of L-Cysteine For Hair Growth

L-cysteine is an amino acid used by the body for metabolic functions and for forming proteins and has been known to help stimulate hair growth. In this article, we outline 7 of the most important benefits of l-cysteine for hair growth.

Benefits Of L-Cysteine For Hair Growth

What is l-cysteine?

L-cysteine is what is known as a non-essential amino acid. A non-essential amino acid is one that our body can produce on its own if we can’t absorb it through diet. 

Some other non-essential amino acids include:

  • Tyrosine
  • Arginine
  • Glutamic Acid
  • Glycine

While l-cysteine is considered non-essential, that doesn’t mean it doesn’t have benefits for our bodies. 

L-cysteine has been found to improve hair growth and metabolic function. It is also a transporter of other nutrients.

7 Important Benefits Of L-Cysteine For Hair Growth

Woman is smiling and looking into the mirror and touching her curly hair at the same time

There are several different ways that l-cysteine benefits hair growth. These include:

1. Forms disulfide bonds that hold together keratin

L-cysteine is an important component of hair strength. One of the ways it does this is by forming disulfide bonds. 

L-cysteine is a sulfur amino acid which is why it is key to forming these bonds. According to the National Library of Medicine, l-cysteine creates these bonds to strengthen the keratin protein.

This is because of the specific family this protein comes from.

They performed a study that showed l-cysteine was one of the critical components of keratin expression. 

Keratin is one of the proteins responsible for hair, skin, and nail growth. 

So the more substantial the bonds of the protein stronger your hair will be.

2. Maintains texture and thickness

Because keratin is such an important part of hair growth, l-cysteine is vital for maintaining texture and thickness. 

This doesn’t necessarily mean that l-cysteine stimulates more hair growth. Rather, because your hair is stronger, you will have less breakage. 

So your hair will be able to grow thicker because you will be losing less hair to breakage.

 L-cysteine may also help your hair follicles produce stronger hairs. 

However, if you want to stimulate more hair growth instead of stronger hair growth, you will need to talk to your doctor about what treatment is right for you.

 L-cysteine will only help support and strengthen current hair growth, not create new growth. 

3. Makes up 10-14% of skin and hair

Studies have found that 10-14% of our skin and hair are made up of l-cysteine. 

Because of this, it’s vital to ensure that your body is producing an adequate amount. If not, then you may need to boost your body’s l-cysteine content through diet and oral supplements.

But be sure to contact your doctor to ensure you don’t have an underlying condition affecting your body’s ability to produce l-cysteine.

4. L-cysteine in hair is a key indicator of hair health

L-cysteine is necessary for hair growth. So, the content of l-cysteine found in your hair follicles is a key indicator of how healthy your hair is.

If your hair lacks l-cysteine and you struggle with hair loss or breakage, it may mean that your hair is missing the critical compounds for building strong keratin bonds.

Conversely, if you have an average amount of l-cysteine in your hair but are still struggling with breakage, then you may be missing a different compound.

5. Can be used to prevent and treat alopecia

L-cysteine also benefits those who have lost their hair due to alopecia. 

Alopecia is an auto-immune disorder that causes hair to fall out in large clumps. Basically, the immune system begins attacking the hair follicles, making it more difficult to grow back.

However, a recent study published by the National Library of Medicine shows that l-cysteine may be used to combat hair loss, including that caused by alopecia. 

The study found that l-cysteine, in tandem with three other compounds, significantly increased the production of hair follicles.

They also found that l-cysteine played a crucial role in protecting the hair from UV damage and oxidative stress. 

Both of these can increase breakage, ultimately leading to hair loss. So l-cysteine is a key component of protecting your hair!

6. Transports essential nutrients responsible for hair growth

In addition to building strong bonds in your hair, l-cysteine is also responsible for transporting other nutrients responsible for hair growth. 

These nutrients include iron and zinc. A lack of both of these nutrients can negatively impact hair growth.

L-cysteine also supports the body’s metabolic functions. So, in addition to transporting these nutrients, it also helps the body break them down into a form it can more readily use. 

Since a deficiency in iron and zinc can cause hair loss, it is vital to have adequate amounts of l-cysteine in your system to absorb these nutrients readily!

7. Helps prevent hair loss and breakage brought on by iron deficiency

Iron deficiency, a common affliction that many women face, actually causes hair loss and breakage. 

That’s because iron deficiency causes a reduction in a process called keratin synthesis that takes place in the hair follicle. This process is responsible for hair growth.

Because l-cysteine is a carrier for iron, it helps make iron more available to an iron-deficient person. This makes it easier for that person’s body to absorb the iron.

Another study published by the National Library of Medicine found that l-cysteine plays a crucial role in formulating and regulating keratin.

This may be another reason why it is so good at combatting hair loss due to iron deficiency.

Is l-cysteine the only compound you can take?

Benefits Of L-Cysteine For Hair Growth

There are other compounds that work in tandem with l-cysteine to improve hair growth. 

These include:

  • Tyrosine
  • Iron 
  • Zinc
  • Methionine
  • Proline
  • Lysine
  • Arginine
  • Glycine
  • Biotin
  • Collagen
  • Keratin

These can be ingested like a supplement, or some can be hair treatments that are applied directly to the hair follicle. 

One of these treatments may be a keratin hair mask. Talk to your hair stylist or dermatologist to get the best treatment for you.

Will taking l-cysteine always work?

There is no cure-all treatment for anything, and that includes hair loss. 

If you’ve tried taking l-cysteine or a supplement with it as an ingredient and you still aren’t seeing any results, you should visit your doctor. 

You may have an underlying condition affecting hair growth.

If that is the case, your doctor may prescribe you a different medication that would be more effective in treating your condition. So always speak with your doctor first.

What is the best way to take l-cysteine?

woman with long light brown hair is smiling and looking into the camera

L-cysteine is available in several different forms. One of the ways you can take it is in a pill. 

You can also take it with the other compounds that boost hair growth to increase its effectiveness. 

However, before you start taking any new medications, you should consult your doctor.

L-cysteine can also be found in different foods. 

If you aren’t ready to take the leap into a supplement, try adding some of these foods into your diet:

  • Lean pork
  • Beef
  • Chicken
  • Tuna
  • Beans
  • Oatmeal
  • Eggs
  • Yogurt


L-cysteine has many important benefits to hair growth. Whether you are currently battling a hair loss condition or simply want to get longer, stronger hair, l-cysteine could help.

Before adding any new supplements to your health regimen, be sure to talk to your doctor to make sure you won’t be interacting with any of your current medications.

Good luck on your hair growth journey.


Effects of the Usage of l-Cysteine (l-Cys) on Human Health

L-Cysteine: the Antioxidant Amino Acid that Boosts Lung and Brain Function

Cysteine Prevents the Reduction in Keratin Synthesis Induced by Iron Deficiency in Human Keratinocytes

Top 10 Foods Highest in Cystine (Cysteine)

Disclaimer: This site is not intended to provide professional or medical advice. All of the content on LovedByCurls.com is for informational purposes only. All advice should be followed at your own discretion. Ingredients may change at any time so always check the product label before using. Check our full disclaimer policy here.