Role of proteins and amino acids in hair growth

By December 15, 2019 December 18th, 2019 Biology, Food for thought

Your hair is made up of protein, called “keratin”, which in turn is made up of amino acids – organic compounds which your body breaks down from the consumption of protein. Your body needs to “decide” where and how those amino acids need to be re-built to make up for any shortages. Lower consumption of protein is linked to breakage in hair and slow hair growth. Here we present the biochemical explanations of these processes, as well as highlighting the importance of consuming appropriate amounts of protein in hair growth.

Why protein is important to hair health?

Your hair is made up 85-90% of 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 bodies don’t naturally produce, therefore needing external injection in the form of supplements. If your protein levels are too low then the protein you consume will go to more essential functions, like supporting muscular-skeletal and cardiovascular function, rather than hair growth. Your body will neglect scalp and hair if chronic protein deficiency is present for too long. So while short-term shortages are acceptable, balanced diet supplemented with vitamins and amino acids is the sustainable approach that will secure long-term health for your hair.

A word on keratin

Hair shaft consists of 3 different types of bonds: hydrogen, salt and disulphide bonds. Hydrogen bonding allows our hair to change shape temporarily and produces a strong hold. While disulphide bonds are stronger and more permanent, thus requiring strong chemicals to break them, such as ammonium thioglycolate – chemical used in perms. Keratin is high in sulphur and the biggest component of the disulphide 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 molecules of keratin missing, often lack lustre and prone to breakage as the disulphide bonds are broken within the hair shaft, thus weakening them.

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 your body needs: whether it is muscle tissue or keratin structures – your body needs to consume enough protein in order to supply hair with necessary building blocks. Supplementing a balanced nutrition with amino acids is a good idea, as some key amino acids are not directly produced by your body. So taking into the necessary amount of protein (roughly 0.8g per kilo of weight) so that your body can regulate itself and decide which type of amino acid it needs to produce – can be a good start.

Main two groups of keratin-associated proteins (KAPs) rich in the amino acids cysteine and glycine, essentially being the building blocks of this critical protein in hair growth.


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

Best sources of Cysteine: The major dietary sources of cysteine include broccoli, chicken, 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 meat, dairy products, fish, spinach, beans, cabbage, soybeans, and banana.

Keratin treatments

We should mention a word or two on keratin treatments. The process involves opening the hair cuticle to make it susceptible to absorption of keratin. Then, ingesting the hair shaft with keratin and sealing it back for smoothness, manageability and shine. This process can visibly “repair” a damaged hair shaft, however 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. 

Rather, a more sustainable way to top up your keratin levels would be from within: balanced nutrition with necessary amount of whole proteins supplemented with key aminos; cysteine and glycine as building blocks of keratin in your hair follicle. 

Want to learn more about importance of nutrition in hair health? Find out more here what to eat to grow your hair >


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)

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