The average person has hair growth of approximately one-half inch per month. Diets consisting of protein, fruits, vegetables, fat and carbohydrates are important. Deficiencies in any of these nutrients will usually manifest themselves in the hair first. Vitamin deficiency can cause slow hair growth. Shedding and hair loss can be caused by mild cases of anemia which is a result of vitamin deficiency.

The B group of vitamins, especially biotin, B₅, and B₁₂, are the most important for healthy hair. They are water soluble. Large doses of the vitamins have no reported side effects.

B₅, also known as pantothenic acid, is an essential nutrient for many animals. Proteins, carbohydrates and fats are synthesized and metabolized with its usage. The name is derived from the Greek word, pantothen, meaning "from everywhere." Nearly every food contains small quantities of B₅. Whole-grain, legumes, eggs, meat, yogurt, avocados and royal jelly are excellent sources of pantothenic acid.

Preserving food, increased packaging and fast food availability have reduced the levels of B vitamins. That is partially why, the cosmetic industry has begun adding pantothenic acid to cosmetic products. Skin irritation and loss of hair color in mouse models have improved with the use of B₅. The benefit in human trials is questionable.

Weak scientific data exists about biotin also. An excess of the daily requirement of biotin is produced by intestinal bacteria. Signs and symptoms of a deficiency in biotin include hair loss. Cradle cap, also known as seborrheic dermititis, may be caused in infants that have a poor ability to use biotin. The condition has been known to improve with the use of increased dietary biotin. The low possibility of side effects makes it easy to recommend for strengthening hair, nails and skin disorders.

Beer has been suggested as a hair enhancing agent. That is because, biotin is found in yeast. Beer contains yeast. Biotin is necessary for healthy hair growth. Shampoos and conditioners that contain biotin allow better absorption and smell better. Biotin aids in the metabolism of amino acids and other nutrients. Men and women who have taken a hair supplement that contain biotin have reported a noticeable difference in hair growth.

Vitamins for hair should include amino acids and zinc also. A lack of zinc can cause hair shedding. Commercial suppliers of nutritional supplements claim that the amino acid PABA (para-aminobenzoic acid) benefits those with premature grey hair.

B₁₂ helps prevent the loss of hair. It also prevents dry scalp and dull hair color. The best hair supplements contain true niacin. A proper dose is around 35 mg. True niacin increases the blood flow to the skin surface.