Although the hair is thought of as dead, it is still a good indicator of general health. In fact, it is the first indicator that reveals signs of ill health or lack of essential vitamins and minerals within the body. For example: Brittle or dry hair can indicate a deficiency in essential fats. Oily hair can indicate a deficiency in vitamin B. A dull hair color and poor growth can indicate a deficiency in zinc. Hair loss can indicate a lack of vitamin C, vitamin B1, iron, and lysine.