At the age of 37 years, one cannot really be said to be "suffering from" gray hair, as it is a normal part of the ageing process. It is in fact probably the most innocuous sign of aging, as it does not really affect your body in any way. For most of your life, cells in your hair follicles produce a pigment known as melanin, which gives your hair its color. This is the same pigment that is produced all over your skin and gives your skin its color, but for some reason, as you grow older hair follicles start to decrease or stop production of melanin. As a result, new hairs that grow do not contain melanin and are therefore colorless. (Hair appears gray because of the mix of black and white hairs.)
This is merely a cosmetic change - it does not affect the quality of your hair or its strength. Gray hair is not any more likely to fall out or get damaged than black hair, and it is in fact completely healthy and normal, except that it does not contain the pigment melanin. If balding is in your genes (if you are a man), then that is unfortunately another age related change that you will have to deal with - but if it is not, then you should be glad that you at least have your hair, whether it is black or gray.
There is nothing you can do to stop, reverse, or even slow down graying of hair. This is true even in the case of premature graying of hair, but in your case, graying is not even premature. At the age of 37, gray hair is unlikely to look odd on you, unless you lose most of your hair color very rapidly. If this is the case, or if you just don't want gray hair yet, the only option is to dye your hair. If you want a more natural option, you can use henna, but this will give your hair a reddish tinge that you may not like. If you decide to dye your hair, you may want to get it done professionally, as it is very difficult to get a very natural look from dyeing your hair at home.
There is one thing that you can do that might possibly slow down the graying, or at least avoid hastening the process - if you smoke, you should stop smoking.
answered by G M