Role of protein and amino acids in hair growth10 min read

Consuming protein is not only great for the muscles, but it also benefits your hair growth. Hair strands consists of keratin, a type of protein, but you need to ensure you consume the right amino acids – the building blocks of the protein – in order to grow healthy hair. In this article, we will first look at the biology and hair structure, understand what is an “essential” vs “non-essential” amino acids, what happens to your hair when there is shortage of protein and how you can tackle protein shortage to nourish your hair follicles for developing strong roots and hair.

Biology of protein in hair structure

There are two types of protein present in your hair – one throughout your hair lengths, and another – at the root of your hair.

Protein in hair lengths

Your hair strands consist of protein, called “keratin”, and keratin consists of amino acids – organic compounds which your body breaks down from the protein you consume. When taken through supplements or as part of your diet and nutrition, your body identifies areas of amino acid shortage and decides which areas need a top up. It may not always go to your hair, even though it may be your preferred area of protein focus.

Protein in your hair roots

Another part of your hair where a type of protein is present – is the inner lining which has molecules of collagen. During growth stage of hair (anagen), your hair follicle has increased amount of collagen in the lining of the hair bulb.

Because hair growth and hair health is on the lower list of priorities, especially in situations of hormonal imbalance or periods of high stress, your hair will suffer first if there is a shortage of protein and amino acids. As a result, low protein levels can lead to breakage in hair and slow hair growth simply because your body lacks those building blocks.

In addition lack of protein in your diet can lead to hair loss if your body de-prioritises hair health further, in favour of supporting more life-supporting functions in your body.

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.

Let’s look at the difference between an essential vs non-essential amino acid in the context of hair:

  • A “non-essential” amino acid is the one that your body can produce itself – from other amino acids you consume as food or supplements. In hair growth, cysteine is a non-essential amino acid, necessary for construction of hair. Cysteine is metabolised from methionine – which is an “essential” amino acid.
  • An “essential” amino-acid is the one your body can’t naturally produce and needs. To manufacture cysteine, your body needs an external intake of methionine.

Shortage of protein can stunt hair growth

If protein levels are too low, the protein that you consume goes to life-supporting functions: such as muscular-skeletal and cardiovascular systems – rather than hair growth. Thus, in case of an on-going protein deficiency, body curbs amino acids sent for hair growth and hair follicles, in favour of making sure that your body can still build and support muscles and tendons. This leads to poor hair health, hair breakage, stunted hair growth and hair loss as result of shortened phase of anagen (growth stage of hair).

Short-term protein shortages are acceptable, but a balanced diet for hair growth supplemented with vitamins and amino acids is what would uphold your long-term hair health.

Some vitamins (e.g. vitamin B1) is essential to metabolise the protein you consume into the amino acids your hair needs. And, since the vitamin density and content in our food has decreased dramatically over the last 100 years, supplementation becomes ever more important and diet alone would be insufficient for healthy hair growth.

Keratin is the protein which makes up hair, but what else?

Hair shaft consists of 3 different types of bonds: hydrogen, salt (saline) and disulphide bonds.

Hydrogen bonds allow our hair to change shape temporarily and produces a flexible hold. An example of that would be a blow dry, curling or straightening your hair with a heat styling tool.

Salt (saline) bonds are responsible for hair’s strength and a consistent percentage of hair’s elasticity. They are created between the positive end of one amino acid chain and the negative end of another. Which is why they are also known as “ionic” bonds in hair. Like hydrogen bonds, these are also temporary and weaker bonds which also are normally broken by water or heat.  

Disulphide bonds are stronger and more permanent, thus requiring strong chemicals to break them. For example in chemical perms a strong chemical – ammonium thioglycolate – is used to break those disulphide bonds that leads to permanent change in hair structure.

Hair shafts with missing molecules of keratin often lack lustre and are prone to breakage, because broken disulphide bonds within the hair shaft weaken the shaft.

What keratin in hair is made of?

Keratin is high in sulphur, the largest component of the disulphide bonds. Sulphur in hair is made up from cysteine, which is replenished through a healthy diet rich in methionine to manufacture it – and some supplementation. Low amounts of methionine, and therefore lack of sulphur can lead to thinning hair and especially hair breakage, and – as a result of it – split ends.

Disulphide bonds are further nourished by natural hair products, gentle styling and hair care methods.

Food sources of protein for hair

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 the muscle tissue or keratin structures in your hair, your body needs to consume enough protein in order to break them into amino acids to create necessary building blocks.

Since some key amino acids are not directly produced by your body, you need to supplement it with balanced nutrition or with amino acid supplements. 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 – is a good start.

Protein digestion and hair growth

There is a significant overlap in the type of foods that can top up your levels of protein and amino acids to help your hair growth. But increasing levels of protein alone, isn’t enough and you need to ensure you supplement it with vitamins and appropriate levels of fibre.

Plant-based protein sources though already containing a number of micronutrients and vitamins, need to be supplemented with vitamin B12, vitamin D, the omega-3 fatty acid DHA, iron and zinc – for them to be successfully metabolised into amino acids.

While you can get those partially from the foods you eat, taking supplements would ensure you meet your daily recommended dose. If you are keen to get these from the food alone you need to be mindful of some vitamins reacting or even being destroyed by heat. For example to support your iron intake it helps to combine your cooked spinach (naturally rich in iron) with vitamin C-rich broccoli. Both will also contribute to your uptake of fiber necessary to keep body & scalp inflammation at bay.

Let’s look at two groups of keratin-associated proteins that are high in the amino acids: cysteine and glycine. Both being the building blocks of this critical protein for hair growth:


Cysteine is, inarguably, the most crucial of amino acids for hair growth. It establishes disulphide bonds in hair. In a number of clinical studies, diets supplemented with cysteine reduced hair loss in subjects over the period of 6 months.

Best food sources of Cysteine: Your body can manufacture cysteine from methionine, an essential amino acid. The major dietary sources of methionine include eggs, beef liver, broccoli, wheat germ, Brussels sprouts, and some dairy products like milk and yogurt. Daily RDA of methionine for an adult of 68kg weight is 1.1g.

Glycine and collagen

Glycine is one of the main building blocks of collagen, the most abundant protein in your body. Collagen is important for hair growth because it lines the hair follicle supporting the anagen (growth) stage of your hair.

While ingesting collagen isn’t the direct 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, cartilage, blood, bones, ligaments – and hair. Another way to manufacture collagen locally on your scalp is through dermarolling.

Collagen production also needs support of proper hydration – therefore drinking sufficient amounts of water for hair growth (at least 2.7 litres for women, and 3.7l for men per day) is essential for production of collagen in your skin and scalp.

Best food sources of Glycine: since glycine is a non-essential amino acid, your body can manufacture it. To supply the building blocks for it, consume foods dairy products – greek yoghurt, certain cheeses (parmesan, mozzarella), seeds – especially sesame seeds, lean turkey, soybeans. Daily RDA of glycine is 2-5g.

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 which is your scalp. Read more here >>

Who we are:

The Hair Fuel is an all-natural hair growth mask created by Laura Sagen, who lost a third of her hair after a terrible visit to a hairdresser while suffering from a life-long condition of PCOS associated with androgenic hair thinning. She developed the formulation rooted in the science of scalp blood flow, which has become The Hair Fuel growth mask. Since then, her company has helped thousands of people like you to start growing healthy hair.

We work closely with our lab and manufacturers to ensure the highest quality product. But 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 tailored advice, digital tools, and online support is 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)

Vitamin C and amino acid metabolism (4)

In Vitro Differences Between Keratinocyte Stem Cells and Transit-Amplifying Cells of the Human Hair Follicle (5)

Sulphur content of hair and of nails in abnormal states (6)

Sulphur-containing Amino Acids: Protective Role Against Free Radicals and Heavy Metals (7)

The sulfur-containing amino acids: an overview (8)


How to grow healthy hair in Spring 2022


How to treat hair loss from thyroid disease

6 thoughts on “Role of protein and amino acids in hair growth<span class="wtr-time-wrap after-title"><span class="wtr-time-number">10</span> min read</span>”

  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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