7. BALANCED VITAMIN INTAKE - Mineral deficiency could cause slowness of hair growth. You need the balance of vitamins A, C, and E in order to promote facial hair growth to a certain degree. These vitamins help to maintain your follicles and sebum and improve circulation to create a better environment for your beard to grow. You can find them in citrus fruits, tomatoes, potatoes, green peppers and other dark leafy green vegetables.