Keratin

Structure and Classification

Keratins are classified into two main structural families based on the molecular organization of the protein chain:

• Alpha-Keratin — a helical structure typical of Hair, Wool, and the stratum Corneum of the Skin. It is the predominant form in mammals. Its flexibility depends on the density of the disulfide bonds formed between Cystine residues.
• Beta-Keratin — a pleated sheet structure found in Feathers, Claws, and reptile Scales. It provides greater rigidity than the alpha form.

At the Amino Acid level, Keratin is characterized by a high concentration of Cystine, Proline, and Serine. It is the disulfide bonds between the cystine chains that determine the mechanical strength of the hair fiber and the hardness of the nail plate: the more numerous and orderly they are, the more compact the structure becomes and the more resistant it is to physical and chemical stress.

Hydrolyzed Keratin: its form in Supplements

Native Keratin is insoluble in water and is not absorbed in its intact form by the digestive system. For nutraceutical use, Hydrolyzed Keratin is employed: the protein undergoes enzymatic or chemical hydrolysis, which breaks down the polypeptide chain into fragments with lower molecular weights, significantly increasing its solubility and intestinal bioavailability.

Sources of Hydrolyzed Keratin for dietary supplements primarily include sheep’s wool and poultry feathers, both of which are rich in Alpha-Keratin. For the Vegetarian and Vegan markets, Amino Acid complexes with a profile similar to that of Keratin, derived from plant-based sources, are used.

The available evidence on Hydrolyzed Keratin pertains to its role in supporting the structure of Hair and Nails: clinical studies have observed a possible improvement in the tensile strength of hair fibers, a reduction in brittleness, and positive results regarding shine, particularly when combined with other hair-nourishing nutrients such as Biotin, Zinc and Selenium.

Biological role and mechanism of action

In hair, the cortex — the middle layer of the hair shaft — is composed of Alpha-Keratin filaments interwoven into supramolecular structures that provide Elasticity, Strength, and Shine. The outer cuticle, formed by overlapping scales of Keratin, protects the cortex from chemical and physical agents.

When endogenous Keratin synthesis decreases — due to nutritional deficiencies, chronic stress, hormonal imbalances, or aging — the most common signs of hair fiber deterioration become apparent: Brittleness, increased Porosity, Loss of Elasticity and Dullness. In Nails, a reduction in keratin density manifests as flaking and brittleness of the nail plate.

Formulation Interactions

Hydrolyzed Keratin works synergistically with other active ingredients in the Hair Care and Skin Health segments:

• Biotin — a coenzyme essential for the metabolism of Amino Acids that are precursors to Keratin and for the synthesis of Fatty acids in the keratinocyte membrane
• Zinc — a cofactor for enzymes involved in keratinization and follicular cell proliferation
• Selenomethionine — protects protein structures from Oxidative Stress during the keratinization process
• Vitamin C — supports the synthesis of Marine Collagen, a structural protein of the hair follicle’s connective tissue framework
• Organic silicon — promotes mineralization and the compactness of the keratinized structures of nails and hair

Hydrolyzed Keratin is generally well tolerated at the recommended doses. If you have a documented allergy to animal proteins (sheep, beef, poultry), you should check the source of the product before taking it. If you are pregnant or breastfeeding, it is recommended that you consult your doctor before starting any supplementation.

Please remember that it is always important to consult a healthcare professional before starting any new supplement or treatment.