Re: Is there any treatment to stop hair whitening in young people?

Dear Christer,

Hair coloration is due to the presence of a pigment called melanin which 
is produced by cells in the hair follicle. A typical hair has a lifespan 
of 4-5 years, after which the hair falls out and is replaced with a new 
hair by the follicle. After about ten of these cycles, the hair follicles 
begin to produce less melanin, and graying may begin in the 30s, with the 
loss of pigment continues until the hair becomes completely white. This 
process is largely determined by genetics, and nutritional supplements, 
vitamins, or drugs are not able to stop its onset. Some people may never 
go completely gray, others may end up with ‘salt-and-pepper’ hair 
throughout the rest of their life, while still others may lose color 
altogether and be left with completely white hair. Caucasians tend to 
start graying in their 30s, those of African descent around 10 years 
later, while Asians tend to keep their pigment still longer. Premature 
graying can take place in an individual in their 20s. This is usually due 
to genetic factors, but may also be caused by disease, medication, or poor 
nutrition.

 http://www.health.uab.edu/show.asp?
durki=79438&site=734&return=18687

Van Neste D, Tobin DJ, Hair cycle and hair pigmentation: dynamic 
interactions and changes associated with aging. Micron 2004;35(3):193-200.