Taking sufficient amounts of essential nutrients in the daily diet has a direct effect on hair health.  Hair loss could occur due to inadequate nutrition.  The  lack of Vitamin B6, for example, can cause the hair to fall out and a deficiency in folic acid could cause baldness.  Take these vitamins liberally, however, and the hair grows back.

PABA (Para-aminobenzoic acid), which is typically found in B-complex supplement, restores hair color, thus eliminating gray hair which is caused by stress or nutritional deficiency.  Grey hair can also be minimized by taking supplemental copper. 

Hair and scalp can also become dry when deficient in Vitamin A causing the hair to be coarse and ugly- especially if protein is also lacking.  Luxuriant hair needs adequate protein.  In fact, hair is made of 88% protein.  Women require 60 grams of protein per day, men 80 to 90 grams and adolescent boys and girls 80 to 100 grams.

Inositol is said to promote healthy hair and hair growth.  Insufficient intake may cause hair loss.  Research has shown, however, that women have a low inositol requirement.  Although this vitamin may help to stimulate the growth of a woman's hair, its lack is probably not a major cause of slow growth.  Women are generally deficient in iodine and Vitamin B1, either of which can slow down circulation in the scalp to such an extent that hair may fall out and cause new hair to grow in very slowly.  Women who keep their diets adequate in iodine, the B vitamins, iron and copper have a better growth of hair, and prevent premature aging.  Iodine is necessary for the healthy functioning of the thyroid gland and its deficiency can lead to many hair problems.   Copper is an essential ingredient in melanin, the pigment that colors hair and skin.  Zinc may be especially beneficial for people who have brittle or thinning hair as a results of an under-active thyroid.  Severe zinc deficiency in humans has been shown to produce baldness and scalp problems that were reversed when zinc was returned to the diet.  Zinc has also been shown to keep hair from turning gray.  Just as with selenium, it aids in immune functions and in the utilization of protein that the body needs to help produce hair.  Zinc and copper are best consumed together to maintain a proper mineral balance.  A deficiency of iron is the cause of dull and brittle hair and if not corrected, can lead to hair loss.  Sulphur and iodine play an important protective role.