Another consideration in choosing food for healthy and shiny hair is avoiding foods that contain goitrogens, sulfur compounds that interfere with the thyroid's ability to process thyroid hormone.
Eating too much cabbage, broccoli, kale, turnip, kale, collards, kohlrabi, spinach, walnut, peach, or conventionally produced strawberries (because they are treated with bromides) can slow down the thyroid enough to induce brittle hair and hair loss, along with dry skin. Eating these foods raw has a greater anti-thyroid effect than eating them cooked, but excessive quantities are a problem no matter how they are prepared.
Water is also important to the health of your hair. You not only need to drink enough water, you need to drink the right kind. Hard water (water than causes calcium buildup in pipes) in particular is a problem, because the calcium in hard water can interfere with the absorption of zinc.
Generally speaking, if your tap water is hard enough to require use of a water softener, you may also need to take a zinc supplement to keep healthy hair. A daily dose of just 15 mg a day, combined with 1 mg of copper and trace elements, is usually enough for normal hair growth. Women who are vegetarians may need additional zinc during pregnancy.
Your choices of the foods you eat is not the only factor in the nutrition of your hair. Some other important considerations include:
- Alcohol consumption. German researchers have learned that men and women who drink alcohol in excess tend to have lower essential fatty acids levels in their hair, so much lower that fatty acid levels in hair can be used as a tool of crime scene investigation. Drinking too much alcohol of any kind can cause dull, lack-luster hair.
- Biotin. The B vitamin biotin is essential healthy skin and continued growth of hair. Biotin deficiency is rare, but it can occur in people who use take R-lipoic acid or alpha-lipoic acids without also taking B vitamin supplements, and in those who consume protein powers made with raw egg white or who eat large quantities of raw eggs. The raw white, not the yolk, interferes with biotin absorption.
- Medication. We all know that most forms of chemotherapy cause hair loss, but dull and flat hair with a tendency to fall out is also a common complication of ACE inhibitors for high blood pressure, oral contraceptives, beta-blockers for high blood pressure or tremors, anti-seizure medications, Accutane and Retin-A for acne, heparin, Coumadin (warfarin), and testosterone injections. Changing or stopping a particular brand of the contraceptive Pill also can cause loss of body in the hair or even hair falling out.
- Riboflavin. The B vitamin riboflavin seems to protect the scalp against infestations with the microscopic skin mite Demodex folliculorum, a tiny animal that is involved in hair loss and the adult form of acne known as rosacea. It's only necessary to avoid riboflavin deficiency; taking large doses of riboflavin has no effect on the skin.
- Sun exposure. As women age, the vitality of their hair is inversely related to accumulated sun exposure. Wearing hats or using hair care products that contain sunscreen is important for preventing aging of the hair as well as aging of the skin.
- Vitamin D. Scientists have only recently realized that vitamin D is important in regulating the cycles of hair growth and follicle renewal. A hair gel containing a form of vitamin D called calcitriol even protects against hair loss caused by some, but not all, forms of chemotherapy for cancer.
Except for protein deficiency, changes in your hair due to poor nutrition are slow to show up, and positive changes in your hair due to good nutrition are even slower. Generally it takes three to four months for an undesirable change in diet other than protein deficiency to cause hair loss, and four to six months for restoration of good dietary habits to cause hair to regrow.
Protein deficiency acts more quickly and is reversed more quickly. Inadequate consumption of protein can result in loss of hair in as little as 10 days, while resumption of adequate protein in the diet can begin to restore hair loss in as little as 10 days. Hair can fall out completely in as little as 14 days with no protein at all in the diet, but begin to grow back completely just 14 days after protein in the diet is restored.