To understand what makes our hair turn gray, we need to first talk about what makes our hair grow and give it color.
A person’s hair color is the result of pigments known as melanin. Made from two amino acids (tyrosine and phenylalanine), these pigments are produced by a specialized group of cells known as melanocytes. They do this through a process called melanogenesis. Melanocytes are found throughout our body and the melanin they produce is what gives our skin, hair, and eyes their color. The melanocytes responsible for hair color are found in the bulbs of your hair follicles.
Even though there is a wide range of hair and skin color, there are only two main types of melanin- eumelanin is what produces dark browns and blacks, and pheomelanin produces reddish/yellow. How these cells blend together will determine what color your hair will be.
It isn’t fully known what makes the melanocytes blend together in the ways they do, to make the specific hair color for each individual. What is known is that there appears to be clear genetic factors. One gene, and its alleles responsible for red hair, have already been identified; known as MC1R, this is also the same gene responsible for red pigments in several other species, like cows.
Once the specific formulation of melanin is produced, their granules are transferred to adjacent keratinocytes, also found in the bulbs of your hair follicles. Keratinocytes are what produce keratine, the dead protein cells that make up our hair. Once a Keratinocyte undergoes its scheduled death, it retains the melanin making our hair color what it is.
Gray hair is the result of less melanin within the keratin. The less melanin, the more gray your hair will be. White hair has no melanin at all.
There are a few different processes that can make our hair turn gray. The one most people think of is the natural graying that occurs as we grow older. As we age our melanocytes become inactive, but are still present. The older we get, melanocytes decrease in number. The result is less and less melanin, until none are present. Thus, we slowly turn gray, and then our hair turns white in the winter of our lives.
In February of 2005, Harvard scientists proposed a theory as to why melanocytes decrease as we age. They found that a failure of melanocyte stem cells was the cause. These stem cells stop producing adequate numbers of melanocytes to maintain our color.
In 2009, scientists in Europe found another contributing factor. They found that hair follicles produce small amounts of hydrogen peroxide. As any teenager preparing for a concert knows, if you expose your hair to hydrogen peroxide, it will make your hair lighter. Bleached hair anyone?!! Normally this small amount of hydrogen peroxide is broken down by an enzyme called catalase. As we age, catalase production is reduced. The result is a build up of hydrogen peroxide, which blocks melanin production by melanocytes.
There are several other things that can cause our hair to turn gray. The exact mediating factor of them isn’t fully known. Some include: genetic defects; abnormal hormone production like in the case of sudden or chronic stress; abnormal body distribution of melanin; and climate factors can also cause graying, such as pollutants, toxins, and chemical exposure.
Let me touch a little bit on why stress causes gray hair. In 2011, the 2012 Nobel Prize winner in Chemistry, Robert Lefkowitz, led a research group that discovered the mechanism that could explain why stress causes graying. Stress causes a release of numerous neurotransmitters involved in our fight or flight response. Normally the release of these neurotransmitters is short lived and has very beneficial attributes- the ability to run from a chasing lion, or avoid an oncoming car to name a couple. Long term production of these neurotransmitters, however, can cause DNA damage. This damage was shown by this group to promote aging, the growth of tumors, miscarriages, psychiatric conditions, and graying of hair. Yes, I did say psychiatric conditions. It seems to me Mr. Lefkowitz just proved why old gray-haired people are sometimes crazy!
The time and speed at which you will gray varies greatly. It’s determined by many, if not all, of the factors we talked about. Your genetic predisposition, chemical exposures, and the levels of chronic stress throughout your life to name a few. If you are Caucasian, however, I can say that 50% of you will be 50% gray by age 50. So in other words, flip a coin if you want to know if you will be gray by 50.
If you liked this article and the Bonus Facts below, you might also like:
- Why Does Hair Only Grow to a Certain Length
- Why Does Chemotherapy Make Hair Fall Out
- There is No Difference Between Fur and Hair
- Shaving Does Not Make Your Hair Grow Back Thicker or Faster
- The average scalp has 100-150 thousand hairs. Hair is so strong that if you made all of your hair into a rope, it could hold 10-15 tons or about 3.5 ounces per strand. Hair also has the highest rate of cell division in the body. It grows at .3mm per day on average, and 1 cm per month. Thankfully, each hair has its own life cycle. If it didn’t, instead of losing hair randomly, we would molt.
- Hair grows in three phases: Anagen- The active growth stage (80-85% of hair is in this phase); Catagen- This phase is also known as the transitional phase, when hair begins to stop growing; and telogen- this phase is when hair growth is completely shut down and the fibers fall out (10-15% of our hair is in this phase at any given time). After your hair goes through the Telogen phase, Anagen begins again and voila! More hair!
- Melanin is a common amino acid in most all living organisms on planet Earth. Interestingly, spiders are one of only a few species that do not produce melanin.
- Criminals beware! Scientists have now developed a way to tell what color your eyes and hair are through the DNA left at a crime scene.
- Ever wonder whether you should spell it gray or grey? It really depends on what part of the world you are in. In Britain, Canada, Australia, Ireland, New Zealand, and South Africa, the spelling is commonly “grey”. In the United States, the preferred spelling is “gray”, although “grey” is also accepted. “Gray” became the preferred spelling in America around 1825.
[Image via Shutterstock]
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