i have a premature grew(white)hairs?

I m 18 year old.and my hair is almost grey.its impressed this possible to convert my grey hair into its natural or black colour through natural diet and remidies

Grey hair in 20s is known as premature grey hair and most commonly occurs due to heredity. Other causes include vitamin deficiency (such as the vitamin B12), stress, medical conditions like thyroid imbalance, smoking. Rule out the cause and treat accordingly.