Amino acids are the building blocks of protein molecules and have a role in virtually all the biological processes that take place in the body. The sequence in which are combined together, determines the structure and function of the protein molecule they produce.  

Sources of amino acids  

Essential amino acids are those which must be obtained through good dietary intake of protein rich foods or supplements because the body is unable to generate these amino acids on its own.

The body’s digestive system breaks down proteins present as polypeptides in dietary sources, into active amino acids, with the help of proteolytic enzymes known as protases, proteinase or peptidase, along with pepsin, trypsin and chymotrypsin. The amino acids are absorbed into the bloodstream through the small intestine and circulated throughout the body to carry out their actions.  

In contrast, non-essential amino acids can be produced or synthesised within the body itself. Deficiency of these amino acids is rare but many manifest during long term illness, nutritional deficiencies or starvation.  

Amino acids that have been found to greatly benefit skin care are:  

a.      Essential amino acids like:  

1.      Histidine

2.      Filaggrin

3.      Urocanic acid

4.      Lysine

5.      Branched chain amino acids: Isoleucine, Leucine and Valine

6.      Phenylalanine and Tyrosine

7.      Tryptophan

8.      Sulphur-Containing Amino Acids: Methionine and Cysteine

9.      Threonine  

b.      Non-essential amino acids like:  

1.      Arginine

2.      Glycine and Proline

3.      Serine and alanine

4.      Glutamine and Glutamate

5.      Aspartic acid  and asparagine 

 Functions of amino acids in the skin  

The skin undergoes its own self repair processes for skin health, which are largely regulated by different proteins. Therefore the quality and quantity of  amino acids present, greatly influence the appearance of the skin. The acids that work especially well on the skin and are readily absorbed from topical applications like arginine, lysine, histidine, glycine, and leucine. 

Amino acids, whether absorbed topically or through a mindful diet, help to form the  most abundant fibrous proteins in the skin, which are keratins, collagen and elastin. They are also used in the manufacturing of synthetic peptides, which are active ingredients in many skin care products.  

In addition, they also help in :  

(a)    Wound healing: Amino acids promote repair of the damaged skin by increasing collagen production and improving the defensive skin barrier..

(b)    Hydration of the skin: The molecules maintain acid-base balance and promote water retention in the skin cell layers, which helps in delaying the appearance of fine lines or wrinkles as it helps to keep the skin plump, even and smooth.

(c)    Protection: Amino acids prevent damage to collagen proteins due to skin exposure to UV rays in sunlight

(d)   Reducing inflammation due to active, anti-bacterial properties, keeping acne under control.

(e)   Anti-ageing efforts: Amino acids like arginine are active collagen boosters that help to smoothen out the skin, making it look young and taut. This works well in under eye creams to strengthen and brighten the sensitive skin around the eyes

(f)     Maintenance of an appropriate skin microbiome.

(g)    Growth and maintenance of  healthy hair: The hair shaft is composed of keratin protein which in turn is made up of different types of amino acids, out of which cysteine is present in abundance. Cysteine, glutamine and lysine strengthen the hair shaft and hair root, while methionine slows greying of hair and prevents hair loss. Tyrosine  protects the hair from UV damage and proline produces collagen to improve quality and texture of the hair.  

Several factors like  ultraviolet (UV) irradiation, atmospheric air dryness, chemical stimulation, malnutrition, and exposure to free radicals are responsible for skin aging, especially wrinkling and sagging as well as hair loss. Therefore, a good balance of dietary and topical amino acids can help to reduce visible signs of ageing and dryness of the skin. The maintenance of skin structures by self-repair processes is essential to skin health. Thus, amino acids can significantly impact the skin’s appearance.

 Amino acids pair well with other skin active ingredients like hyaluronic acid and glycerine to promote moisturization. They also work with collagen to reduce the appearance of fine lines or wrinkles and with ceramides to protect the skin from damage.

References 

1.Murakami H, Shimbo K, Inoue Y, Takino Y, Kobayashi H. Importance of amino acid composition to improve skin collagen protein synthesis rates in UV-irradiated mice. Amino Acids. 2012;42(6):2481-2489. doi:10.1007/s00726-011-1059-z 

2.Solano F. Metabolism and functions of amino acids in the skin. Adv Exp Med Biol. 2020;1265:187–99. 

3.https://www.healthline.com/health/peptides-for-skin 

4.Murakami H, Shimbo K, Inoue Y, Takino Y, Kobayashi H. Importance of amino acid composition to improve skin collagen protein synthesis rates in UV-irradiated mice. Amino Acids. 2012;42(6):2481-2489. doi:10.1007/s00726-011-1059-z