Despite the fact that everyone sooner or later faces such a phenomenon as hair color turning first into gray and then into white, the real cause of this is known to few people.
Why people have different hair color
The reason why we all have different hair color is because of the melanin pigment (from the Greek melanos meaning “black”) in our hair cells. It is also responsible for the color of the skin and eyes. This pigment is produced by specialized skin cells called melanocytes. They are located at the bottom of the outer layer of the skin – the epidermis (from the Greek epi – “on” and derma – “skin”). When ultraviolet light penetrates them through the upper layers, they begin to produce melanin.
The pigment has to be transferred to the overlying layers. This is done by special melanophore cells (from melanin + Greek phoros – “carrier”). They deliver melanin to the keratinocytes. These are the main cells of the epidermis, and they are what we mean when we say “skin”. Keratinocytes also make up the outer layer of the hair.
The main function of melanin is to protect against ultraviolet rays. Coloring in different colors is a byproduct of this function.
What are the dangers of ultraviolet light
UV light causes changes in nucleic acids (DNA and RNA). These changes affect cell growth, division, and heredity, i.e., the basic life activity of the cell. DNA stores “blueprints” of how the cell should be organized. And if these “blueprints” are changed, the cell itself changes with them (mutation). And these changes can be irreparable and lead to serious disorders of both the cell and the organism as a whole.
Since the DNA is stored in the nucleus of the cell, it is the nucleus that needs the best protection. Melanin granules accumulate around the nucleus and form a shield that protects against ultraviolet light.
What hair color depends on
Melanin comes in two colors, black-brown and red. The black-brown one is called eumelanin. Red is pheomelanin. It is because of the high content of pheomelanin that our lips are red. But if you have a lot of it in your hair, it will be red. That is assuming that there is little black pigment. But if there is a lot of both, then the hair will have a deep brown color. If there is a lot of black pigment and not enough red, then the hair will be black. A light color is characteristic of hair with little of either pigment.
Mixing these two colors in different proportions, like watercolor paints, and you get more than 300 different shades.
Considering that the main function of melanin is to protect against ultraviolet light, we can think of the color of the hair of the natives of different countries. Those people whose ancestors lived closer to the equator usually have dark hair.
Why are Africans black if darker heat is stronger
Similarly with skin color. The more ultraviolet light, the more melanin, and therefore the darker the skin. Africa has the most ultraviolet light, which is why indigenous Africans have brown or black skin.
But melanin protects against ultraviolet light, but not against overheating. A black body reflects less light and absorbs most of it. And along with the light, it absorbs the energy that the light carries. The more light absorbed, the more energy absorbed. And that energy raises the temperature of the body. So people with black skin absorb about 30% more energy than people with white skin. That’s why people with black skin sweat more to compensate for overheating.
In addition, the melanin barrier hinders the passage of ultraviolet light, which is necessary for vitamin D synthesis. So children with black skin are more prone to rickets because of its deficiency.
Why hair loses color
As people get older, their bodies start to perform worse. This includes melanocytes. They begin to produce less melanin, which causes the color of the hair to lighten, gradually turning gray, and then, white.
In addition, hair cells produce hydrogen peroxide during their vital activity. Normally, this peroxide is broken down into water and oxygen by a special enzyme called katalase (from Greek katalio – “to destroy”, “to break” + suffix “aza” – indicating that this substance belongs to enzymes). But in the process of aging, the production of this enzyme is disrupted, and peroxide destroys melanin.
Если вам есть что дополнить в статье — напишите это в комментариях.
