Keratin, a type of fibrous structural protein, is a key component of hair, nails, claws, hooves, horns, fur, feathers, and scales.
Skin, Hair, & Nails
Skin, hair, and nails are all part of our integumentary system (i.e., the body’s outer layer), which includes all of the organs (and their appendages) that form the outermost layer of the body. Alongside its protective role, this system is also important for aesthetic purposes. A number of treatments (dietary, supplementary, and topical) have been studied for hair and skin health.
The most noteworthy skin-related issues that individuals experience are aging, acne, eczema (e.g., atopic dermatitis), and skin cancer. Hair-related issues include hair loss, breaking, and graying. Nail-related issues include brittleness, discoloration, and fungal infections. Age, damage (e.g., physical trauma, exposure to certain chemicals or radiation), oxidative stress, and inflammation can all lead to problems with skin, hair, and nails.
The integumentary system is complex and requires many nutrients to function correctly. As such, a diet that provides adequate levels of nutrients — notably, protein, certain micronutrients (e.g, cysteine, lysine, iron, vitamin A, vitamin C, B vitamins, zinc, selenium), and essential fatty acids such as omega-6 and omega-3 polyunsaturated fatty acids — is important. Not only are these nutrients necessary for ordinary function, but they also play a role in protection and repair (e.g., in response to UV radiation). Deficiencies in these nutrients may manifest as abnormalities in skin, hair, and nails.
Cysteine, lysine, marine proteins (i.e., extracellular matrix components from sharks and mollusks), procyanidins, pumpkin seed oil, B vitamins, vitamin D, vitamin E derivatives, and zinc have all been studied for hair loss.
There isn’t much research on supplementation for nails, although it’s possible that hair supplements may benefit them because they’re made of similar materials.