Hello XXXXXXX
Thanks for the query.
Graying of hair is part of the aging process, and as yet, science has not found a way to stop or reverse this graying of hair.
In fact in most cases even premature graying of hair cannot be stopped or reversed. Many people do not start turning gray till 40, however it is not really considered unnatural for gray hair to appear around the age of 30. If your hair starts turning gray during childhood or in your teens however, this is considered to be premature graying of hair.
 As mentioned however, there is usually nothing that can be done about it. Usually the condition is entirely benign and is therefore nothing to worry about. If the gray hair bothers you, you can always die it, although many people find this to be an unnecessary bother and expense.
Gray hair is actually not gray but white or rather colorless - as part of the aging process, and sometimes prematurely, the body stops producing the pigment that normally gives hair its color. In the majority of cases, the cause of premature graying are genetic, and therefore beyond our control. There are a few medical conditions that have premature graying as a symptom, but these are likely to have other more prominent symptoms.Only in a very small percentage of cases are there factors such as diet or lifestyle that cause graying of hair. Two lifestyle factors that can contribute to premature graying are stress and smoking. If you think either of these could be a factor for you, you should address them as soon as possible, not just because they affect your hair, but because they affect your overall health quite drastically.
Lack of nutrition can also cause hair to appear gray. This is technically not really premature graying - due to nutritional deficiencies, hair may become thin and light. To the casual eye, this seems like graying of hair. However, this problem can usually be fixed quite easily, simply by following a more balanced diet that includes a wide range of foods, particularly fruits And vegetables.

Nutrition deficiency: Improper intake of nutrients in the diet is one of the primary causes of premature graying of hair. Lack of some of vitamins B, iron, copper and iodine in the daily diet are believed to be a contributing factor.
Medical conditions: Certain medical conditions like Thyroid imbalance,vitiligo, anemia, etc. are said to be associated with premature graying of hair.
In generalized hair loss, there is a uniform thinning over the entire scalp with no areas of normal hair growth.
The medical term for hair loss is alopecia. Two important types of alopecia responsible for baldness are

Alopecia totalis is an uncommon condition in which all hair on the scalp is lost. The cause is unknown, and the baldness is usually permanent.
and
Androgenetic alopecia is balding caused by heredity. It can affect both men and women, although women with this inherited tendency do not become totally bald. The condition can start in a person's teens, twenties, or thirties.
Treatments for this condition are designed to reverse the normal and natural course of events. Ways to restore hair in men who are balding include:

Camouflage techniques
Plastic surgery techniques
Drug treatments
You must consult a dermatologist for finding the cause for premature greying and take the treatment if reason could be found.
And you may consult hair clinics and find the ways for restoration of your hair.
I hope to have answered your query however you may revert to me for any further query.
Thanks and best of luck.

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