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Why will our hair turn white when we grow old?
When new hair grows from a hair follicle with no melanocyte stem cell, the hair would appear white or gray.
(Posted on 12 April 2007)
Q1. Why our hair turn white when we grow old?
A1. A growing hair is initially colorless (or white). The color of our hair comes from a pigment called "melanin". There are different kinds of melanin, depending on variations in molecular structure. Melanin is produced by specialized cells called "melanocytes". They are abundant on the skin and are also lining the hair follicles.
As the hair grows, melanocytes in the hair follicle deposit melanin on it. People with different genetic background are genetically programmed to have different combinations of melanin pigments laid down on their hair as it grows.
Melanocytes in the hair follicles are specialized cells derived from undifferentiated stem cells situated in a special pocket halfway up the hair follicle. People's hair turns white or gray at roughly the same age as their parents. Scientists believe that the melanocyte stem cells in the hair follicles are programmed by our DNA to die after the individual has reached a certain age. As we get older, there are fewer and fewer melanocyte stem cells in the pocket of a hair follicle. When new hair grows from a hair follicle with no melanocyte stem cell, the hair would be unpigmented, because there is no melanocyte to lay down melanin. The hair would appear white or gray.
Q2. Some young people find they have white hair too. How can we explain this phenomenon?
A2. White hair is more noticeable in people with darker hair because it stands out. People can get white hair at any age. Whereas most may be in their 30s or 40s before they see white hair, some may have white hair soon after their teens. In extreme cases, people may be born with white hair. Albinism is a group of genetic disorders in which the affected individual has reduced or absent pigmentation, affecting the color of skin, hair and eyes.
Genetics appears to play an important role in deciding at what age our hair starts to turn white. This means that most of us will start having gray hairs around the same age that our parents or grandparents first did. Environmental factors may be important too. Smokers are found to be four times more likely to turn white prematurely compared to nonsmokers, according to a study published in the British Medical Journal.
There are no special diets, nutritional supplements, vitamins, nor proteins that have been proven to slow, stop, or in any way affect the graying process, although many have been marketed over the years. It is normal to find a few strands of white hair in young individuals, even children. This has nothing to do with premature aging.
Q3. Why stress will cause hair loss?
A3. Our hair grows in cycles that last from two to seven years. During the growing phase it gains about 1 centimeter a month in length. After the growing phase it would not grow any longer. The strand of hair would stay in the hair follicle, only to be shed as a normal part of washing or brushing. A new hair will start growing from the empty hair follicle afterwards, repeating the cycle once again.
90 percent of the hair will be in the growing phase at any one time on the scalp of a healthy individual. About 10 percent would be in resting phase. With acute physical and psychological stress, the body would shut down hair growth through changes in hormone levels. That means a much higher proportion of hair would be in the resting phase after acute stress. They are all destined to be shed within the next 3 months after the stress is over. That is when the patient would notice unusual number of loose strands falling on her pillows. By then the patient might have forgotten about the stressful episode.
People under psychological stress may also develop nervous habits, such as scalp rubbing or hair twisting or pulling that can cause hair loss through mechanical means that they are not aware of.
Not all cases of hair loss are caused by stress. Since hair loss may be an early sign of a disease, it is important to find the cause so that it can be treated.
Source: Quality HealthCare
