Is L-Cysteine For Hair Is Secret to Gorgeous Hair?

Smiling woman twirling her brown locks

Have you ever browsed the hair care aisle for that miracle product for healthier locks? While commercial products can certainly offer benefits, the power of nutrients should not be overlooked. In this blog post, I will sift through the research on the amino acid L-cysteine and its impact on hair growth, separating fact from fiction. 

Overview of Hair Loss

Hair loss can be influenced by various factors, and understanding the role of amino acids in this process is essential. Amino acids are the building blocks of proteins, crucial for the structure of human hair. Hair strands are composed of a protein called keratin, which relies on amino acids for its formation. 

L-cysteine, in particular, plays a significant role in supporting hair growth. It is involved in the synthesis of keratin and contributes to the health of hair follicles. A deficiency in essential amino acids may impact the overall protein structure of hair, potentially leading to weakened strands and increased susceptibility to hair loss. Ensuring an adequate supply of amino acids through a balanced diet can play a vital role in improving hair growth and maintaining healthy hair follicles within the human body.

The Structure of Hair

Your hair is a resilient and adaptable structure composed of three crucial layers. The outermost layer, the cuticle, acts as a protective shield for the inner components and forms a barrier that safeguards the underlying layers. Directly beneath the cuticle lies the cortex. 

This cortex layer is home to a vital protein called keratin, playing a central role in the overall health of your hair. The cortex functions as the powerhouse, influencing your hair’s strength, flexibility, and vibrancy. The next time you appreciate your hair, recognize that its beauty goes beyond appearances – a collaboration of these three layers working to ensure your hair is robust, elastic, and uniquely yours! There are many types of keratins; some also have regulatory functions and are involved in intracellular signaling pathways, such as protection from stress, wound healing, and apoptosis. 

The medulla, also called the pith or marrow of the hair, is the innermost layer. Composed of round cells, this layer is normally found in thick or coarse hair. Not all hair has a medulla.

Visual breakdown of hair's internal structure

Why Is Keratin So Important? 

Keratin is a protein that plays a crucial role in shaping the structure of our hair. Think of it as the building blocks of your hair. This incredible protein is not just a simple structure; it comprises long chains of amino acids like tiny puzzle pieces that fit together perfectly. When you hear about keratin, think of it as the powerhouse protein that gives your hair strength, structure, and beautiful bounce! 

Red hair with the title The Connection Between Keratin and Cysteine.

The Connection Between Keratin and Cysteine

Cysteine, also known as L-cysteine, is an amino acid that helps create proteins in our body, and one of its essential tasks is forming keratin. Cysteine does its magic by building disulfide bridges within the keratin protein. These bridges act like tiny reinforcements, adding strength and rigidity to your hair so it doesn’t break easily. The cool part is that cysteine is found in different foods, and our bodies can make it. 

Can L-Cysteine Be Used For Improving Hair Growth?

Let’s dig into the question: Can L-cysteine help your hair grow? Some studies have investigated this, concluding that L-cysteine might be a key player in promoting hair growth. How does it work? As mentioned above, L-cysteine helps make keratin, which makes hair strong and healthy. If your hair is strong and healthy, it will continue to grow! 

Iron Deficiency and Supplementing With Cysteine

Iron deficiency can significantly impact the expression of keratin, a crucial protein for the health and strength of our hair. When the body lacks sufficient iron, keratin production can decrease, affecting our hair’s overall condition. 

However, an exciting finding suggests that supplementing with cysteine can counteract the adverse effects of iron deficiency on cellular keratin expression. This means that by providing the body with additional cysteine, we may help mitigate the impact of insufficient iron levels, potentially supporting the synthesis of keratin and promoting healthier hair. 

How Much Cysteine Should I Take? 

There’s no one-size-fits-all answer. We know that a balanced and diverse diet with foods rich in L-cysteine can help meet your nutritional needs for healthy hair. L-cysteine is found in poultry, eggs, dairy products, nuts, seeds, and grains. 

Active woman surrounded by diverse foods

Focus on a Well-Balanced Diet

A well-balanced diet is like giving your body the right tools to make your hair strong and vibrant. But here’s the critical part: everyone is a bit different, and what works for one person might not work for another. That’s why chatting with a healthcare professional or a registered dietitian is a good idea. They can give you personalized advice to determine the right amount of L-cysteine for your hair journey.

Food Sources of L-Cysteine 

L-cysteine is naturally present in various high-protein foods, including plant proteins, making it accessible through a well-balanced diet.

Finding L-Cysteine in food

By incorporating a diverse range of high-protein foods into one’s diet, individuals can naturally obtain L-cysteine and support the body’s overall health and well-being.

Debunking a Myth: Human Hair is Found In Store Bread

The claim that human hair is used in bread production is a misconception and stretches far. While it is true that L-cysteine, an amino acid derived from various sources, including human hair, is used as a dough conditioner during the baking process to extend the shelf life of some baked goods, it is not a widespread practice in the bread industry. 

Most L-cysteine used in food production is sourced from other, more readily available sources such as poultry feathers or produced through microbial fermentation. Additionally, the amount of L-cysteine used in bread is typically minimal, and it undergoes thorough processing, rendering it safe for consumption. It’s important to dispel this myth and recognize that using human hair in bread is not a common or standard practice in the food industry.

Still disgusted and want to play it safe?  Make your own bread or find a local bakery transparent about its ingredients.  

N-Acetyl Cysteine

When considering L-cysteine supplementation, N-acetyl cysteine (NAC) is frequently chosen for its efficacy and practical application in promoting overall well-being. Determining the appropriate dosage of L-cysteine is essential for reaping its potential benefits while minimizing the risk of adverse effects. While there is no established Recommended Dietary Allowance (RDA) for L-cysteine, specific health goals and conditions often influence dosages. 

Individual needs may differ based on age, weight, and overall health. It may be helpful to start with a lower dosage and gradually increase it under the guidance of a healthcare professional. Additionally, obtaining L-cysteine from natural food sources is a safe and effective way to incorporate it into the diet.

Joyful woman with curls twirling her hair

L-Cysteine for Hair and Beyond

Cysteine doesn’t just stop at making your hair strong. First, L-cysteine is like an antioxidant champion, which means it helps fight off the bad stuff that can cause damage to your body. So, it’s not only good for your hair but for your overall health. 

And here’s the bonus: L-cysteine also plays a role in making collagen. Collagen is like the glue that holds your skin and nails together, ensuring they stay healthy and happy. So, when you think about L-cysteine, think beyond just hair – it’s a multitasking amino acid that keeps you looking and feeling your best!

Is L-Cysteine the Only Amino Acid For Healthy Hair Growth?

Several amino acids play a pivotal role in maintaining healthy hair. They serve as the building blocks of proteins, particularly keratin, the hair’s main structural component. Essential amino acids, such as cysteine, methionine, and lysine, contribute significantly to the strength and resilience of hair strands. A balanced, protein-rich diet that includes these essential amino acids is key to nurturing vibrant, lustrous, and healthy hair from within.

Beneficial Amino Acids

  • Cysteine, in particular, is crucial for forming disulfide bonds, which provide the hair shaft with structural integrity. 
  • Methionine aids in keratin production, while lysine influences the protein’s cross-linking, enhancing the overall hair quality. 
  • Additionally, arginine promotes blood circulation to the hair follicles, ensuring they receive essential nutrients for optimal growth. 


Incorporating L-cysteine-rich foods into your diet and considering the potential benefits of glycine may be valuable steps in promoting hair growth and overall health. Supplementing with NAC is beneficial if you struggle to eat foods high in various amino acids. 

It is important to approach nutritional choices holistically and consult a healthcare professional or registered dietitian to ensure a well-rounded and personalized approach to your dietary needs. Remember, beautiful and healthy hair starts from within.

Frequently Asked Questions

What are the side effects of taking L-cysteine?

Side effects of taking L-cysteine may include nausea, vomiting, diarrhea, and allergic reactions. Excessive intake may lead to an imbalance of amino acids. It’s crucial to consult with a healthcare professional for personalized advice.

Can I take L-cysteine every day?

Whether you can take a form of L-cysteine every day depends on individual health and needs. It’s important to follow recommended dosage guidelines and consult a healthcare provider to determine what’s appropriate.

Which amino acid is best for hair growth?

L-cysteine is often mentioned for hair growth as it is a component of keratin, the protein that makes up hair. Other amino acids like biotin, arginine, and methionine are also believed to contribute to hair health.

What are the benefits of L-cysteine?

L-cysteine has several benefits, including its role in protein synthesis, antioxidant properties, and hair, skin, and nail health support. It is also involved in the synthesis of glutathione, an important antioxidant. Some studies suggest potential benefits for liver protection and respiratory health. Consult with a healthcare professional before starting any supplement regimen.


April Bruns | Registered Dietitian | ACE Personal Trainer

April Bruns | Registered Dietitian | ACE Personal Trainer

April is a registered dietitian and freelance health and wellness writer. She holds a BS in Food Science and Human Nutrition from Washington State University. She works as a private practice dietitian specializing in weight loss, gut health, and functional fitness.

Learn More About April

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