Pre mature greying : Men start graying closer to 30, while women begin to notice gray hairs around 35, Causes of pre mature greying are Genetics, Stress, Auto immune disease, Thyroid disorder, Vit B12 deficiency n Smoking. Eating more antioxidants: A person's diet plays a part in preventing white hair. A diet rich in antioxidants can reduce oxidative stress. Antioxidant-rich foods include: fresh fruits and vegetables.