It depends on the specific cause of your gray hair.

The graying of hair is a natural occurrence as human beings age or mature. There are times however when graying or whitening of hair prematurely. You may be able to prevent this however, depending on the cause of your hair's premature graying.

Quitting Smoking Can Prevent Premature Gray Hair

According to one study, there is a significant relationship between grey hair and smoking. Six hundred and six (606) individuals were examined in this study, where approximately half of the participants were smokers. According to this study, the participants who were smokers had a higher incidence of gray hair, and this was consistently observed in the smoking group, regardless of their ages or sex. The study thus concluded that quitting smoking can prevent premature gray hair. 

Lowering Stress Levels May Prevent Premature Gray Hair

Although there are no studies that have provided us with evidence that stress does indeed directly cause the premature graying of hair, scientists are beginning to uncover indications in their research these two incidents. In support of this theory, it has also been found in a separate study that severe emotional stress does directly cause the body cells to age at a faster rate. Thus, it may be helpful to lower your stress levels or learn how to deal with your stress in a more positive and effective manner in order to prevent premature gray hair.

Genes and Ethnicity

If premature gray hair can be observed within your family, it is more than likely that you will have premature gray hair as well. Thus, you will not be able to prevent premature gray hair if you are genetically predisposed to it.

The same is true for the premature graying of hair that is determined by ethnic background. One study shows that Caucasians are more predisposed to having premature gray hair than their Asian and African-American counterparts.