Why your hair turns gray as you age?

 

Why does hair go grey?

Natural hair gets its color from a pigment called melanin. The type and amount of melanin determines each person’s hair color. Melanin is produced by melanocyte cells. These cells are located in the (deepest) basal layer of the skin, just above the hair papilla (the bottom part of the hair follicle).

There are two types of melanin. Eumelanin is a dark pigment that is responsible for brown and black hair. Pheomelanin is a reddish pigment that results in ginger and strawberry blond hair types. Blond hair happens when melanocytes produce low levels of eumelanin.

Type of melanin based on hair color:

·         Black: lots of eumelanin

·         Brown: average amount of eumelanin

·         Blonde: little eumelanin

·         Red: lots of pheomelanin and small amount of eumelanin

Melanocytes infuse melanin into the hair shaft, giving it a distinctive color. Hair goes grey as the body ages because there are fewer melanocytes and melanin production decreases. Air pockets replace melanin in the hair shaft, resulting in silver-grey hair, and grey pubic hair too.

Reports have suggested that the leading cause of gray hair is oxidative stress, a process where free radicals damage cells, including melanocytes. Free radicals are particles that are derived from everything from pollution to fried foods which are often absent in our diets.

 

Grey hair and genetics

The average age for grey hair varies greatly, and one of the main causes of grey hair in your 20s is genetics. The age at which a person’s hair turns grey is influenced by the IRF4 gene, and one specific variant (rs12203592) is a marker for premature greying.

The IFR4 gene controls that activity of another gene called TYR, which encodes an enzyme that is needed for melanin production. It has been suggested that the rs12203592 variant affects the activity of melanocyte precursor cells, but it’s currently unclear whether this hypothesis is correct.

 

Other causes of grey hair

In addition to ageing, other causes of grey hair include genetics, stress, nutrient deficiencies, and health problems. These factors affect how melanocytes function and can cause premature grey hair by lowering the production of pigment.

 

Stress and grey hair

There are several ways in which psychological stress can affect the hair shaft. The most common hair-related side effect of stress is telogen effluvium, which makes hair fall out about three times faster than usual. In middle age and later, the hair may grow back grey.

In rare cases, hair may suddenly turn white. This condition is known as Marie Antoinette Syndrome, whose hair reportedly went grey overnight before her beheading.

But does stress cause grey hair? In humans, we don’t know. One study in mice showed that, when exposed to stress, their fur turns grey, but whether this is true in humans remains unknown.

 

Nutrient deficiencies

Several micronutrient deficiencies have been detected in people with premature grey hair. Low levels of group B vitamins (folic acid, biotin, and B12), vitamin D, iron, and selenium have been associated with grey hair in childhood and young adults.

 

Smoking

Early grey hair is more likely to affect people who smoke according to a 2013 study. It has been suggested that smoking, like air pollution, generates reactive oxygen species (unstable oxygen molecules) that damage the biochemical process of melanin production.

 

Medical Causes

The vast majority of people with gray hair have age-related graying. However, sometimes graying hair indicates an illness, especially if it occurs at a particularly young age. Health problems that may be heralded by gray hair include:

·         vitamin B₁₂ deficiency

·         neurofibromatosis (also called Von Recklinghausen's disease): this group of inherited diseases causes tumors to grow along nerves and abnormal development of the bones and skin.

·         tuberous sclerosis: an uncommon, inherited condition that causes benign tumors in multiple organs (including the brain, heart, kidneys, eyes, lungs, and skin).

·         thyroid disease

·         vitiligo: this condition causes melanocytes (the cells at the base of hair follicles that produce color) to be lost or destroyed — perhaps because the immune system "misfires" and attacks the scalp rather than an infection.

·         alopecia areata: a disorder in which patches of hair may be suddenly lost, especially the colored (non-gray) hairs. This may lead to "overnight" graying because previously present gray or white hairs suddenly become more obvious. When hair growth resumes, it may be white or gray, but colored hair may eventually return.

 

Mechanism

A study published April 19, 2023, may have answered why our hair turns gray as we age.

Researchers at NYU Grossman School of Medicine studied melanocyte stem cells in mice — a type of cell that’s also found in humans — and discovered that these cells may eventually get “stuck” as one ages, eventually losing the ability to move between growth compartments in hair particles and produce the pigment that provides hair color.

If this result is also applicable to humans, researchers are hopeful it could lead to the discovery of a way to prevent hair from losing its youthful hue.

“The newfound mechanisms raise the possibility that the same fixed-positioning of melanocyte stem cells may exist in humans,” Qi Sun, the study’s lead investigator, said in a press release. “If so, it presents a potential pathway for reversing or preventing the graying of human hair by helping jammed cells to move again between developing hair follicle compartments.”

 

Sources and Additional Information:

https://www.nature.com/articles/s41586-023-05960-6?

https://atlasbiomed.com/blog/grey-hair-causes/

https://www.health.harvard.edu/blog/hair-turn-gray-2017091812226

https://www.scientificamerican.com/article/gray-hair-can-return-to-its-original-color-mdash-and-stress-is-involved-of-course/