Recent research indicates that adequate nutrition and energy needs to be constantly available at the hair follicle for optimal hair growth to occur. As the hair follicle is a non-essential tissue and, therefore, is one of the last tissues to receive its energy supply (or the first to have its energy supply reduced) any long term deficiencies may lead to premature hair loss. Also, hair is one of the fastest growing tissues in the body (it grows approx. 1/2 inch each month) and so any long term reduction in energy or raw materials to the hair follicle will cause the hair cycle to be disturbed. Any nutritional disturbance to the hair follicle will cause the growing (anagen) phase of the hair cycle to become shorter, leading to an increase of shedding, and the resting phase to become longer, slowing regrowth.

The liver maintains a constant level of glucose in the blood and stores several hours (approx. 4-5 hours) reserve of glucose in the form of glycogen. Therefore, it is necessary to eat regularly (every 4 hours) to maintain adequate hair follicle energy levels. Also, sufficient amounts of proteins, minerals, and vitamins in the diet are important for normal hair cell metabolism.

The most common nutritionally related hair loss occurs whilst dieting. Severe weight loss due to dieting can often cause a temporary increase in hair shedding due to metabolic changes to the body. The loss usually begins 2-4 months after the onset of the diet, however, the hair tends to regrow to its original fullness another 2-6 months after the weight has been stabilized.

Other recent research studies have shown that deficiencies in iron stores, vitamin B-12, folic acid, and triglyceride levels can also lead to hair cycle disturbances. Usually, any deficiencies only cause temporary hair loss as, once corrected, hair will regrow normally. However, long term shortages can lead to permanent hair loss and the acceleration of genetic hair loss, if present.

Other influences of diet on hair loss are: certain excesses of some vitamins, particularly the fat soluble vitamin A, and inadequate intake of proteins can reduce the ability of the hair protein, keratin, to be synthesized.