Next to each hair is a sebaceous gland which secrete sebum which lubricates the hair and provides each hair with an element of protection. If the sebaceous glands are overactive greasy or oily hair will result. If the glands are underactive dry hair may result including breakage.
Daily Hair Tip
Always include a little fat in your diet. Fats, especially the good ones, help produce the essential oils that prevent hair from drying out.