Variations in the amount of keratin and melanin determine how dark our skin or hair is. However, these substances don't exist just for aesthetics. Keratin and melanin also have biological functions. It's easier to grasp what these functions are once you know exactly what keratin and melanin are.
Keratin is a tough, insoluble and fibrous protein. The most common places it occurs in people is in hair and nails. However, because its chemical structure makes it so strong, it also occurs in feathers, hooves and horns. According to National Skin Health, keratin is produced by cells in the skin called keratinocytes.
Melanin is a pigment. Cells called melanocytes form melanin in response to exposure to the sun. Specifically, melanin is created when the melanocyte metabolises an amino acid called tyrosine. It's easiest to see in hair and skin, but it also is present in the irises of the eyes, the brainstem and the adrenal gland. Plants also contain melanin.
According to the Johns Hopkins University School of Medicine, the most fundamental role of keratin is to protect cells from any stressors that could result in cell damage and death. Keratin is the most abundant protein in epithelial cells because the skin is the body's primary barrier against the environment. Keratin protects cells in part by providing the matrix around which other tissues can form and stabilise. According to Natural Skin Health, keratin also is responsible for keeping the skin elastic.
The primary function of melanin is to protect the skin and underlying tissue from sun damage. The more melanin a person has the more harmful ultraviolet radiation from the sun he can block. This matters because ultraviolet rays not only can kill cells, but also can cause cells to grow abnormally, forming cancer.
Keratin, Melanin and Diet
Melanin and keratin both depend on the presence of amino acids in the human body to form. Amino acids make up proteins, which are common in foods like tuna, beef or turkey. If you find that you're burning very easily in the sun, your skin doesn't have the bounce it used to have or your hair seems more brittle than usual, it may be because you aren't getting enough protein in your diet. Diet won't change the amount of keratinocytes or melanocytes you have, so you won't go from a fair-skinned individual to looking like chocolate, but dietary change at least enables these cells to function optimally.