Thanks for putting your query on HealthCareMagic. I understand your concerns on premature greying of hair. Hair goes grey when color-producing cells stop producing a pigment called melanin. Naturally occurring hydrogen peroxide can also build up in the hair, bleaching the color. Vitamin B-12 deficiency or problems with your pituitary or thyroid gland can cause premature graying that’s reversible if the problem is corrected. While greying might be irreversible, correction of malnutrition via the right nutrition, can at least prevent it. Regular healthy diet, proper hair and scalp hygiene and de stressing activities may provide some relief. Some people suggest that applying bhingraj oil to the scalp, substituting coffee for green tea and eating vegetables rich in folic acid. It is also advised to quit smoking, avoid stress and an indisciplined lifestyle. Curry leaves (kadi patta) are thought to be effective by some who suggest to include them in your daily diet or to boil them in coconut oil and apply it on your scalp once it cools off. Indian gooseberry which is also known as amla is also thougth to be effective for treating premature greying of hair. Ashwagandha (Indian ginseng) is also applied on scalp to avoid premature greying of hair. Ashwagandha is thought to increase the melanin content in your hair follicle. Other than dyeing the hair black, there is no procedure or medicine to change grey hair into black.