According to Healthline, vitamin D and the B complex vitamins are all important for the growth of strong, healthy hair. Vitamin D, widely recognized for creating strong bones and healthy skin, is also shown to help create new hair follicles.
While all the B-complex vitamins are cited for their ability to help create healthy hair, B-12, niacin and biotin are the most beneficial for adding strength to and conditioning the hair, according to Healthline. These vitamins can be supplemented, but it is widely recommended that food be the main source of these vitamins in the body. Exercising to reduce stress and drinking plenty of water can also help to promote healthy hair.