Hair starts its lifespan in small, sack-like structures in the skin known as follicles. Each follicle produces a single hair shaft composed of a hard protein called keratin, which is arranged in long, tightly bound strands. New growth begins in the follicle and pushes outward so that the oldest part of the hair is furthest from the scalp.
Each hair has a distinct growth cycle — active growth, maturation, and rest. During the resting phase, the follicle relaxes its hold on the shaft, so hair can easily fall or be pulled out. Every hair on your head goes through the growth cycle, but not at the same time. At any given moment, about 15 percent of all the hairs on your head are resting, and therefore capable of shedding . . . in your hairbrush, in the shower, on the bathroom floor. This is totally normal, and is not a harbinger of baldness. Between my two daughters and myself, our shower drain needs cleaning about every two weeks — that’s about all the “resting” hair it can take before it’s thoroughly clogged. Trust me, none of us is even close to bald. But if you have been experiencing unusual hair loss or problems with dryness, splitting, or breakage, or if you simply want to have more beautiful locks, nutrition can help.
What Affects Hair Health?
It is estimated that we each lose about 100 hairs a day. The actual number you’ll lose on any given day depends on how abundant and healthy your follicles are, what medications you’re taking, and many other factors, some of which are beyond your control. For example, the recommendations in this section won’t reverse thinning hair due to male pattern baldness or aging — typical male baldness is genetic. As we age, our hair spends more time in the resting phase, which means that we’ll shed more hair than usual, and it won’t grow back as quickly. For more general hair problems, here are some factors that you should be aware of:
Both male and female hormones affect hair growth. Male hormones known as androgens — a category that includes testosterone — stimulate hair growth on the face and body, and create fuller, thicker hair on the head. In women, ovaries and adrenal glands naturally produce androgens, but only very small amounts. If a woman suddenly starts growing facial hair, she should see her doctor — it could be a sign of a hormone-related health problem.
For some men with a genetic susceptibility to baldness, normal testosterone is converted to a more potent form of testosterone (dihydrotestosterone, or DHT), which binds to cells in the follicle. DHT alters the growth/shed cycle and eventually kills the follicle. These men find themselves becoming bald in their 20s, a few years after their testosterone levels peak. Because the follicle itself shrinks and dies, this type of baldness is irreversible. Some prescription medications may short-circuit the balding process if caught early enough, though the medications need to be continued for life.
In both men and women, levels of androgens decrease after about age 40, which leads to thinner, slower-growing, less luxurious hair as we get older. In contrast to androgens, the female hormone estrogen slows hair growth and creates a finer, thinner shaft of hair, which is why women are, on average, naturally less hairy than men. After menopause, levels of estrogen fall off dramatically, causing some genetically susceptible women to lose significant amounts of hair. Experts believe that female balding follows a processes much like male balding — without enough estrogen to off-set the tiny amounts of androgens in their bodies, they also can have androgen-related hair loss. But male and female hair loss aren’t identical. While men tend to bald in a distinct pattern that includes a receding hairline and hair loss at the crown, women tend to lose hair evenly, leaving them with a sparse head of hair instead of a totally bald scalp.
When levels of estrogen and progesterone are both high, such as during pregnancy, the combination works to synchronize the hair growth cycles, so more hair is in the growth stage at the same time. In the second and third trimester of pregnancy, the percent of hair in the resting phase falls by one-third to about 10 percent. For those few months, pregnant women have the fullest, richest heads of hair they’ll have in their entire lives. About three months after delivery, the percent of shedding hairs goes back up to 15 percent. As all those synchronized hairs enter the resting phase together, it can look like you’re suddenly losing all your hair. Don’t panic! Once the hair starts to regrow, it returns to its usual growth/rest cycle.
Stress is one of the most common causes of unusual hair loss. Accidents, major illnesses, severe psychological stress, or other traumatic events can send hair follicles into the resting phase prematurely. Around three months later, when those resting follicles release the hair shaft, large amounts of hair can seem to fall out simultaneously, and for no discernable reason since several months will have passed since the event that triggered this whole episode. Again, getting through this is simply a matter of waiting it out. Your hair should begin to regrow almost immediately.
Lack of Protein
Hair is made of protein. All basic nutrients contribute to keeping us whole and healthy, but protein provides the building blocks that allow us to repair, replace, or grow bones, skin, muscles, and hair. Although we tend to think of dietary protein as coming from steak, fish, chicken, and other meats, it is also found in eggs, legumes (such as starchy beans and lentils), dairy products, soy foods, and — in smaller amounts — some whole grains and vegetables. People who don’t get enough protein in their diets, such as those with anorexia nervosa or who follow any extreme weight-loss diet, will slow the rate of new hair growth. As hair is naturally shed, it won’t grow back as quickly. With enough hair loss, the scalp will start to show through. Starvation also depletes the body of other nutrients important for hair growth and quality. And over the long term, starvation and extreme weight loss will lead to a reduction in hormone production, which can also lead to thinning hair.
Medications and Supplements
Most people understand that chemotherapy treatments for cancer can cause widespread balding, but many other commonly prescribed medications may lead to less extensive hair loss. These include anticoagulants (such as warfarin), antidepressants, oral contraceptives, and medications for blood pressure, gout, or arthritis. In addition, very high doses of vitamin A and selenium are toxic and can cause hair loss. This type of toxicity happens only if you take high-dose supplements, so don’t take individual supplements for vitamin A or selenium. If you take a multivitamin supplement, it shouldn’t contain more than 100% DV for vitamin A (5,000 IU) or selenium (70 micrograms). Better yet, make sure your multivitamin provides 50 to 100% of its vitamin A in the precursor form of beta carotene and/or mixed carotenoids. There is no known chance of Vitamin A toxicity when you’re getting your standard supplemental dose from carotenoids. Because beta carotene in food and supplements is converted to the active form of vitamin A by your body in controlled amounts, you won’t make more than your body needs. Once you stop taking the medication or supplements, hair will usually begin to grow back within a few months.
Thyroid Gland Malfunction and Other Disorders
Thyroid hormones affect the metabolism of all cells, including cells in hair follicles. Too much thyroid hormone (hyperthyroid) or too little thyroid hormone (hypothyroid) can result in thin, brittle hair or hair loss. With uncontrolled diabetes, body cells (including cells in hair follicles) starve because glucose can’t get in; and in systemic lupus erythematosus, the body attacks its own collagen, including the collagen in hair follicles. These disorders and many others — including celiac disease, rheumatoid arthritis, ulcerative colitis, and Crohn’s disease — may cause hair loss or damage by altering cell metabolism or structure. Once the underlying disease is treated, hair growth should return to normal. All cases of unexplained hair loss should be investigated by a physician to rule out the possibility of serious disease.
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