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Role of protein and amino acids in hair growth

Good news for the body builders, since consuming protein is not only great for the muscles, but also – for the hair growth. For the mere mortals amongst us we might need to take a close look at our diet and supplements. But first, let’s dive into the biology of it all.

Biology of protein in hair structure

Your hair consists of protein, called “keratin”, which in turn consists of amino acids – organic compounds which your body breaks down from the consumption of protein. Your body needs to identify areas of amino acid shortage and decide which ones that need a top up. Lower protein levels can lead to breakage in hair and slow hair growth simply because your body lacks those building blocks.

Why protein is important to hair growth?

Your hair consists of 85-90% keratin – a complex protein that also makes up majority of your skin and nails. In turn, keratin is built up by 18 essential and non-essential acids.

An amino acid being “essential” means our body doesn’t naturally produce it, therefore it needs external injection in the form of supplements or food. If protein levels are too low, the protein goes to more essential functions: supporting muscular-skeletal and cardiovascular function, rather than hair growth. Thus, in case of chronic protein deficiency, body neglects scalp and hair growth. While short-term protein shortages are acceptable, a balanced diet supplemented with vitamins and amino acids puts you on a sustainable path securing long-term hair health.

A word on keratin

Hair shaft consists of 3 different types of bonds: hydrogen, salt (saline) and disulfide bonds. Hydrogen bonding allows our hair to change shape temporarily and produces a flexible hold. Disulfide bonds are stronger and more permanent, thus requiring strong chemicals to break them, such as ammonium thioglycolate – a chemical used in perms. Keratin is high in sulfur and the biggest component of the disulfide bonds. It can be built through a healthy diet, and nourished by natural hair care products, gentle styling and hair care methods. The hair shafts with missing molecules of keratin often lack lustre and are prone to breakage, as the broken disulfide bonds within the hair shaft weaken the shaft.

Protein digestion and hair growth 

Your digestive system breaks down proteins into amino acids that then get diverted into liver to produce more protein in the form that your body requires. Whether it is muscle tissue or keratin structures in hair, your body needs to consume enough protein in order to supply necessary building blocks. Since some key amino acids are not directly produced by your body, it helps to supplement with a balanced nutrition rich with amino acids. Taking into the necessary amount of protein (roughly 0.8g per kilo of weight), so that body can regulate itself and decide which type of amino acid it needs to produce – can be a good start.

Plant-based protein sources contain a number of micronutrients and vitamins, that you need to supplement with vitamin B12, vitamin D, the omega-3 fatty acid DHA, iron and zinc. While you can definitely get those from the foods you eat, it helps to take supplements that contain those nutrients. For example to support your iron intake it helps to combine your cooked spinach (naturally rich in iron) with vitamin C-rich broccoli. It also contributes to your uptake of fiber. In future we explore plant-based diet tweaks and supplmentation for hair health.

Let’s look at two groups of kertain-associated proteins rich in the amino acids cysteine and glycine: the building blocks of this critical protein for hair growth.


Cysteine is, inarguably, the most crucial of amino acids for hair growth. It establishes disulfide bridges, a type of bond that plays a fundamental role in the folding and stabilisation of protein structure: including the bonds within the hair shaft. In a number of clinical studies, diets supplemented with cysteine reduced hair loss in subjects over the period of 6 months.

Best sources of Cysteine: The major dietary sources of cysteine include broccoli, wheat germ, Brussels sprouts, and some dairy products like milk and yogurt.

Glycine and collagen

Glycine is one of the main building blocks of collagen, the most abundant protein in your body. While ingesting collagen isn’t the way to top up the levels of collagen in your hair, supplementing your diet with the building blocks: vitamin C and glycine can provide strength for your muscles, skin, hair cartilage, blood, bones and ligaments.

Best Sources Of Glycine: Your body naturally produces glycine, but it can also be supplemented by foods like dairy products, spinach, beans, cabbage, soybeans, and banana.

Keratin treatments

The process of keratin treatment involves artificially adding keratin to the hair shaft. First, it starts with opening the hair cuticle to make it susceptible to the absorption of keratin. Then, it follows with ingesting the hair shaft with keratin and sealing it back for smoothness, manageability and shine. Though this process can visibly “repair” a damaged hair shaft, it often involves using harsh chemicals such as formaldehyde and high temperatures for sealing and therefore cannot be recommended as an on-going way to support hair health. 

As tempting as it this “fix” sounds, a more sustainable way to top up your keratin levels comes from within. Think balanced nutrition with necessary amount of whole proteins supplemented with key aminos: cysteine and glycine as building blocks of keratin within your hair follicle. 

If you want to understand nutrition to support your hair health, here >> you can find out specific foods to eat in order to grow your hair.

Topical (on-scalp) solutions

The best support for hair growth needs to combine external and internal methods. As you incorporate more proteins into your diet, you need to look into natural products available on the market, specifically those focusing on the blood flow to scalp to ensure that the proteins you consume and the amino acids produced by your body get delivered to the point they need to be: your scalp. Read more here >>

Who we are:

The Hair Fuel is an all-natural hair growth mask created by Laura Sagen, who embarked on her journey of hair regrowth as she lost a third of her hair after one horrendous visit to a hairdresser. Started off as tinkering in the kitchen, she developed the formulation rooted in science of scalp blood flow which she has used for years, before a light bulb moment to offer it to other people. This is what has become The Hair Fuel

We work closely with our lab and manufacturers to ensure the highest quality product. But we know that a product alone is never enough – so we hold your hand throughout your own, unique hair growth journey. Our flagship product – The Hair Fuel mask – coupled with our advice, digital tools and on-going web / chat support are there to help you grow the best hair you can. It’s a big claim – but we’re unafraid to make it. Check out our starter bundles >>


Organization and expression of hair follicle genes, Journal of Investigative Dermatology (1)

The structure of people’s hair (2)

Effects of the Usage of l-Cysteine (l-Cys) on Human Health (3)


Nutrition for hair growth: what to eat to grow your hair


5 must-do hairstyles to try in lockdown

6 thoughts on “Role of protein and amino acids in hair growth”

  1. Thanks for informing me that amino acids would help me get healthy hair long-term. My hair has always been of my biggest insecurities because I don’t know how to tame it. Perhaps it would be beneficial to invest in hair products with amino acids to help make my hair healthier. Thanks!

    • Thanks Levi! Glad you found this helpful. AFAIK, amino acids need to be consumed internally, rather than applied topically, because the molecules are too big to penetrate the skin on scalp… Though can be an interesting area to look into. So far, we have found no evidence of such efficacy. But making sure your nutrition is on point can set you up on a healthy hair path. 😉

  2. Hello, I have a client who came in for an hair and scalp consultation / while reviewing her questionnaire, she stated that she’s Vegan and during her journey as Vegan she began to experience severe hair loss/ She’s in good health, no previous surgeries, no medications, she takes supplements, but her diet is fair / as a result I ruled out the hair loss as being protein deficiency / I found this sight to be very informative, to help me with her treatment plan / thank you

    • Hey Tara! Thanks for your question, we replied in detail to the email you provided. But for the benefit of our readers, generally speaking while we think that the diet we maintain has all the nutrients in it – oftentimes it’s not the case. For example if your client is busy to prepare a balanced meal, it is easy to reach out for “quick fix” snacks that have little nutrients your client hair follicles need. Especially with a vegan diet… there easily a protein and B-vitamin deficiency is common. If this diet change is a recent development – body can be responding to this change as a stress factor. Generally speaking, iron, magnesium (for healthy nervous system), B-complex and A-Z supplemented by a protein shake – is a good go-to recommendation. Having said that, it also helps to explore your client’s stress landscape.


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