Osteoporosis, Calcium, and Estrogen

Food and drug companies are eager to shore up your bones. Calcium supplements abound, and today’s grocery shelves offer a feast of the mineral in products ranging from oatmeal to chewing gum. At breakfast alone, you can toast calcium-fortified bread, wash it down with calcium-fortified orange juice, and even pour calcium-fortified milk on your calcium-fortified cereal.

The calcium craze began innocently enough. In 1984, a panel of scientists convened by the National Institutes of Health (NIH) for a consensus development conference recommended that women obtain more calcium—up to 1500 milligrams (mg) a day. The hope was that additional calcium might help prevent osteoporosis, an abnormal loss of bone most common in postmenopausal women.

In the nutrition arena, even the merest hope has a cash value, especially when that hope is voiced by scientists. Accordingly, when the NIH panel’s advice hit the marketplace, it was suddenly transformed into a national health crusade. Images of stooped women, bent and frail from osteoporosis, became a symbol of what could happen to those who failed to heed advertisements for calcium. Sales of calcium supplements soared—from $47 million to $200 million between 1983 and 1987.

Like many nutrition vogues, however, the calcium bandwagon tends to roll over the facts. By the time the NIH held a follow-up conference in 1987, officials found that they had to contend with widespread misconceptions about osteoporosis and calcium.

Despite what ads may imply, loading up on calcium after menopause won’t promote a straight spine. And even if it could, some brands of supplements offer little help; they are formulated so poorly that the calcium can’t be absorbed by the body. So if you’re anxious to avoid osteoporosis, it’s important to know what calcium can and can’t do for you and how to get what you really need.

Osteoporosis and Calcium Deficiency

Osteoporosis literally means “porous bone.” All adults lose bone as they age, but the excessive loss in osteoporosis makes the skeleton abnormally fragile. An awkward step, a warm hug, or even a strong sneeze may result in fracture.

The disorder afflicts some 15 million Americans, causing at least 1.2 million fractures each year. By age 65, one-third of American women have suffered a vertebral fracture—the kind that contributes to a stoop or “dowager’s hump.” Osteoporosis also causes an estimated 227,000 hip fractures annually, about twice as often in women as in men. For the elderly, a hip fracture is often more than a painful inconvenience; some 12 to 20 percent of victims die from related complications, such as pneumonia or blood clots in the lungs.

Unfortunately, osteoporosis usually goes unnoticed until it’s already severe. By the time ordinary X rays show it, 50 percent of bone mass may be lost. And once bone is lost, it can’t be replenished. As of now, the only hope lies in prevention.

The bones reach their peak density somewhere between ages 30 and 40. Then their density starts to decline. One way to minimize the possibility of severe osteoporosis is to start bone loss from a higher setpoint, in effect, by building sturdy bones while you’re young. Adequate calcium intake during your twenties and thirties can help do that.

Calcium is the most abundant mineral in the body, accounting for up to 2 percent of an adult’s weight. Nearly all of it is found where you might expect—in the bones and teeth. A small remaining fraction in the blood and other tissues plays a critical role in several body processes, including blood clotting, transmission of nerve impulses, hormone action, and muscle function.

Bones are often thought of as inert structures like the steel girders of a building. But they’re actually living tissues in a constant state of flux, continually being broken down (resorption) and reformed (accretion). Usually these two factors balance each other. But when calcium is lost from the body or is poorly provided for or absorbed from the diet, resorption gains the competitive edge.

Many Americans—including the overwhelming majority of women—don’t get enough calcium. Roughly half of men over age 35 and about 85 percent of women over age 20 don’t obtain the Recommended Dietary Allowance for calcium set by the National Academy of Sciences/National Research Council.

The deficit for women is particularly worrisome because nature works against them where calcium is concerned. Women generally have smaller skeletons than men do, and thus lower calcium reserves. Pregnancy, childbirth, and frequent dieting can deplete those reserves further. Hormonal changes that occur at menopause cause women to lose bone seven times faster than men do. So it’s important for women to build up calcium reserves before menopause occurs.

Osteoporosis is not only a disease of calcium deficiency, though. It’s a complex interaction of genetic, hormonal, nutritional, and life-style factors of which calcium is only a part.

Who Is at Risk?

While there’s no way to predict precisely who will and who won’t develop the disease, certain factors point to those at greatest risk.

Genetic Factors Being female is the primary risk. But some women are at higher risk than others. Thin women or women with small bone structures are more susceptible than large, big-boned women. Also, for reasons not entirely understood, the lighter the skin color, the greater the risk. White and Asian women are at much higher risk than black women. Light-skinned, fair-haired women of northern European ancestry are especially vulnerable to the disorder.

Family History A woman who has a mother, sister, grandmother, or aunt with osteoporosis has an increased chance of developing it herself.

Early Menopause The earlier estrogen’ ceases to be secreted by a woman’s ovaries—because of surgical removal of the ovaries or an early menopause—the sooner she loses the hormone’s protective effect on bone.

Other factors that are more controllable can also influence risk. A sedentary life-style, heavy alcohol consumption, smoking, and excessive caffeine intake all have been linked to the chances of developing osteoporosis. Chronic use of medications that increase calcium excretion may also contribute to bone loss. The main ones include corticosteroids, tetracycline, antacids containing aluminum, and certain diuretics.

Preventing Osteoporosis Through Diet

Obtaining enough calcium in your diet eases the drain on your bones. The National Academy of Sciences/National Research Council sets the Recommended Dietary Allowance (RDA) for adults at 800 mg of calcium daily, an amount calculated to meet the nutritional needs of virtually all healthy people other than pregnant or nursing women. The U.S. Food and Drug Administration (FDA) uses a broader guideline, called the U.S. Recommended Daily Allowance (U.S. RDA), which takes the higher needs of teenagers and others into consideration. The U.S. RDA for calcium, which is the one used in food labeling, is 1000 mg daily.

Manufacturers of fortified foods sometimes go to absurd lengths to sidestep the fact that there are excellent, natural sources of calcium.

“Here’s a case for you,” says Angela Lansbury, star of the television series “Murder, She Wrote,” in a commercial for Total cereal. “The case of the missing calcium.” Lansbury then proceeds to search in vain for calcium in competitors’ cereals. You can find it readily enough, though—in the milk you pour on any of them.

Roughly three-fourths of the calcium in our food supply is in dairy products. Even if you don’t drink milk, you can still obtain calcium in a wide range of milk-based products and numerous foods that contain them. Substantial amounts of calcium are found not only in yogurt, cheese, and ice cream, but also in custard, pizza, New England clam chowder, and a host of other foods. You can even consume milk in disguise, adding nonfat-milk powder to sauces, stews, gravies, and casseroles.

Good sources of calcium also include canned salmon and sardines (with soft, edible bones), oysters, almonds, and various green, leafy vegetables. Indeed, many foods contain calcium in at least small to moderate amounts. But unless you’re an avid fan of seafood or greens, you’ll need some dairy foods on your menu. It takes more than a dozen oysters or a heaping plate of kale, for example, to match the calcium in a single glass of milk.

Furthermore, the calcium in dairy products is readily available to your body—something that can’t always be said for other foods, including calcium-fortified products. Milk is fortified with vitamin D, which promotes the absorption of calcium. Spinach and Swiss chard are rich in calcium, but they’re also high in oxalates, which bind calcium and hinder its absorption from the intestine.

Nor will you necessarily do better with a calcium-fortified food. Calcium absorption from most fortified foods is as yet untested. If you depend mainly on fortified products, moreover, you may slight other nutrients. A calcium-fortified fruit drink, for example, won’t give you the protein of milk. Eating a well-balanced diet is the only reliable way to obtain all the nutrients you need—including calcium.

Although dairy products may be high in fat and calories, your choices aren’t limited to ice cream and puddings. Both skim and low-fat milk supply some 300 mg of calcium per cup—at 100 calories or less. At 145 calories, a cup of plain, low-fat yogurt provides 415 mg of calcium. Some cheeses such as Swiss and Muenster do almost as well.

People who are deficient in the intestinal enzyme lactase may have trouble digesting lactose (milk sugar). They may experience gas, bloating, or diarrhea after drinking milk. However, dairy products in which the lactose is already partly broken down—yogurt, buttermilk, and cheeses, for example—often cause no problems. Many people with mild lactase deficiency can also drink modest amounts of milk with a meal. Another alternative is to use a product that supplies lactase such as LactAid or Lactrase. The product is added to milk to convert part or most of the lactose to sugars that are easier to digest. Pretreated milk is also available in several parts of the country.

Preventing Osteoporosis With Calcium Supplements

If postmenopausal women lose calcium at a rapid rate, it would seem logical for them to start taking extra calcium at the onset of menopause. But that logic has proved wanting.

Calcium Versus Estrogen

Research since 1984 shows that taking extra calcium after menopause has only a marginal effect in slowing bone loss. The primary effect is governed by the action of estrogen, one of two female hormones secreted by the ovaries.

Estrogen is essential for preserving bone in women. At menopause, which normally occurs between ages 45 and 55, the ovaries slow their secretion of estrogen. Women then start losing bone at an accelerated rate. The greatest rate of bone loss in a woman’s lifetime occurs during the first five to seven years following menopause. Afterward, bone loss continues but at a slower rate.

A study published in 1987 in The New England Journal of Medicine shows that estrogen, rather than calcium, is the key to slowing bone loss in postmenopausal women. The two-year study, conducted in Denmark, compared three groups of women beginning at the time of menopause. One group was treated with estrogen. Another took 2000 mg of calcium supplements a day. The third, a control group, received placebos. The resulting difference in bone loss was dramatic. Bone density in the estrogen group remained constant, while the other two groups lost significant amounts of bone.

Calcium did have a modest effect compared to the placebo. The women who took calcium lost somewhat less cortical bone—the compact bone found in the hip and forearm. However, calcium ingestion had no effect on the spongy, trabecular bone of the spine. Hence, extra calcium taken after menopause would do nothing to ward off a bent spine.

Even though extra calcium offers only marginal benefits after menopause, CU’s medical consultants agree with the NIH that taking it is reasonable for women at risk. For those women, any additional edge is desirable. Moreover, for people with normal kidney function and no personal or family history of kidney stones, 1500 mg of calcium a day is safe. For all other adults, the NIH panel’s recommendation of 1000 mg daily is a sensible target.

Calcium Supplements

Calcium carbonate is the most widely used form of calcium. If calcium carbonate tablets are not properly formulated, however, they won’t provide the calcium you need. In the body, calcium tablets dissolve only in the acidic environment of the stomach. Performance criteria established by the U.S. Pharmacopeia (USP), the nonprofit organization that sets standards for drugs, require at least 75 percent of a calcium tablet to dissolve within 30 minutes—the amount of time it might remain in the stomach. Otherwise, much of the calcium will pass through the body without being absorbed.

Because calcium supplements are considered foods, not drugs, they aren’t subject to the same efficacy tests as drugs are under federal law. But a product does have to be what the label says it is. It is illegal to sell a calcium supplement that doesn’t provide calcium.

In 1987, Ralph Shangraw, M.D., chairman of the department of pharmaceutics at the University of Maryland School of Pharmacy, tested 80 different calcium supplements. He found that more than half failed to meet USP standards. Consumers Union then performed similar tests on seven nationally available brands of supplements. Four of the seven failed the USP standards.

After Shangraw reported his results at an FDA public conference on osteoporosis, the FDA launched its own field study of calcium supplements. An FDA staff member said the agency will “take action” against manufacturers who fail to meet the USP guidelines for dissolution.

Rather than wait for FDA action, many manufacturers have reformulated their products. But why were so many of the original formulations so inferior? Shangraw offered several reasons. Calcium is bulky. Manufacturers therefore didn’t have room for much filler material, such as starch, which helps tablets break up in the stomach. Moreover, companies found that the words “no sugar, no starch” pumped up sales, and many had already removed starch from their formulas. Finally, because calcium is chalky and difficult to swallow, companies often coated pills with shellac. That hinders stomach acids from dissolving the pills. The resulting product tended to act much like a slick pebble.

Other forms of calcium are also available as supplements. Calcium citrate, calcium lactate, and calcium gluconate, for example, dissolve more reliably than calcium carbonate. Their drawback, however, is that the calcium is far less concentrated. Calcium carbonate is 40 percent calcium—compared with 24 percent for calcium citrate, 18 percent for calcium lactate, and only 9 percent for calcium gluconate. That means you’ll have to take more tablets—and pay more—for an equivalent amount of calcium.

Another form is calcium phosphate. But tests indicate that it is less soluble than calcium carbonate, suggesting that it is not likely to be a good alternative. Nor are supplements featuring dolomite or bone meal. In the past, some samples of those supplements have been contaminated with lead. “Chelated” calcium tablets are also no bargain. Chelation purportedly improves absorption, but it actually does little more than increase the price.

Clearly, all calcium supplements should be required to meet USP standards. Otherwise, there’s no way to be sure the brand you buy will provide calcium in a form your body can use. But even if and when they do consistently meet those standards, you’re better off getting your calcium in food.

Estrogen Replacement Therapy and Menopause

Often the most effective measure for postmenopausal women at risk of osteoporosis is a medical one—estrogen replacement therapy.

Essentially, estrogen replacement therapy involves taking oral doses of estrogen to compensate for the natural decline in its production by the ovaries after menopause. Estrogen can’t restore bone mass, so it’s not an effective therapy for older women who have already lost a great deal of bone. But if estrogen is started soon after menopause, it can prevent the accelerated bone loss that normally occurs during the first five to seven postmenopausal years. Studies show, for example, that the therapy can reduce the incidence of hip and wrist fractures by 60 percent if begun around the time of menopause.

Estrogen as therapy for osteoporosis is actually one of the hormone’s most recent therapeutic applications. Since the 1940s, physicians have prescribed estrogen to afford women relief from the sometimes distressing symptoms of menopause, particularly hot flashes and vaginal atrophy.

Promotional campaigns for estrogen replacement therapy started in the 1960s and, fed by the preaching of a few physicians, flourished for more than a decade. Many menopausal and postmenopausal women were tantalized by the promise that they could remain healthy, youthful, and attractive for the rest of their lives. The promise was summed up in the slogan “Feminine Forever,” which was also the title of the book that helped spark the estrogen boom. Millions of menopausal women without severe symptoms were encouraged to take the drug routinely as a cure-all for aging, for the degenerative diseases associated with aging, and for the emotional difficulties purportedly linked with middle age.

Then reports of another side of estrogen therapy began to circulate. Instead of maintaining health and prolonging life, long-term use of estrogen replacement reportedly caused uterine cancer and increased the risk of gallbladder and cardiovascular disease. For many women the dream of agelessness through drug therapy turned into a nightmare of fear and dread. Estrogen usage dropped sharply.

The 1980s brought a renewed interest in a somewhat different approach to estrogen replacement therapy. The culprit behind the seven-to nine-fold increase in the incidence of uterine cancer was found to be not estrogen per se, but rather the use of unopposed estrogen—that is, estrogen therapy without concomitant use of the female hormone progesterone. Studies showed that women who received combined estrogen/progesterone replacement therapy had no greater incidence of uterine cancer than did a control group of women. Additional studies have confirmed those results, making combined estrogen/progesterone therapy standard practice.

Estrogen replacement therapy is unquestionably effective and appropriate against certain menopausal symptoms in some women. But which symptoms?

There is no question that menopause is dramatic and undeniable evidence of aging and of the loss of reproductive capability—a double blow for some in a society that worships youth, good looks, and sexuality for everyone. Yet despite physical manifestations of the aging process, femininity and sexuality need not decline as hormones decline. Whether in response to their perceived change in status or to hormonal changes, some menopausal women experience a cluster of psychological symptoms. They may feel nervous, tired, or dejected. They may experience sudden mood changes or suffer from insomnia. How much these emotional manifestations are associated with hormonal changes generally or with the specific distress of hot flashes or vaginal atrophy is not known.

Some menopausal women have hot flashes to a disabling degree. As often as 10 to 20 times a day, a wave of heat, lasting from a few seconds to a few minutes, spreads over the chest, neck, and/or head. It is usually accompanied by a “flush,” or increased reddening, and sometimes by drenching sweats. A woman may experience such flashes for only a few months, or they may continue for years. In most cases, they cease within a year or two.

Atrophy of the vaginal lining usually does not develop fully until a decade or so after menstruation ceases, but it can begin sooner. With menopause, vaginal secretions and lubrication may decrease, the vaginal lining begins to thin, and the vagina may become less elastic. Symptoms such as itching, burning, and pain during intercourse may accompany these changes. Urinary discomfort may also occur.

The benefits and risks of treating menopausal and postmenopausal women with estrogen therapy was the subject of a 1979 consensus development conference sponsored by the National Institute on Aging of the National Institutes of Health. The panel’s conclusions supported the judicious use of estrogen therapy in women who suffer from severe hot flashes and vaginal atrophy. But, said the report, “There is no evidence at present to justify the use of estrogens in treatment of primary psychological problems.” And, according to medical authorities, estrogen replacement cannot prevent or reverse the aging process. (The advisability of estrogen therapy for osteoporosis was left unresolved at the time due to insufficient research data. It has since been shown to decrease the incidence of fractures.)

Estrogen therapy still poses certain hazards. It has been found to promote gallstones, rare liver tumors, and blood clotting factors. The issue of estrogen therapy and breast cancer continues to be debated. Most experts agree that estrogen does not cause breast cancer, although it can promote growth of an already existing breast cancer.

Before a woman starts on estrogen replacement, for whatever reasons, her physician should take a careful history and perform a thorough examination. Liver disease, hypertension, smoking, heart disease, or breast or uterine cancer would likely rule out estrogen therapy.

Because of the risks associated with estrogen replacement, therapy should be reevaluated and discontinued periodically to see if symptoms return. Hot flashes usually need to be treated only for a period of months, according to the FDA, and rarely for longer than a year. Vaginal atrophy may require treatment for a much longer time.

For a woman at high risk of osteoporosis, the benefits of estrogen replacement therapy are now believed to far outweigh the drawbacks. In addition, recent research suggests that taking extra calcium along with estrogen may allow the estrogen dose to be cut in half, further reducing any possible harmful effects.

Other Measures for Preventing and Treating Osteoporosis

The spotlight on calcium sometimes obscures the role of other measures to forestall osteoporosis. Among the most important is physical activity, which is vital for preserving bone. The advice here, say experts, is “use it or lose it.” But you don’t have to run marathons or pump iron to benefit. Even light to moderate exercise can increase bone density.

Not all exercise is equally helpful in building bone. The weightless Skylab astronauts were extremely active and yet suffered bone losses comparable to bedridden people. The best exercises appear to be “weight-bearing” ones—the kind that put stress on the limbs through active movement. Good weight-bearing activities include walking, biking, jogging, aerobics, rope jumping, and practically any active sport that gets you to move around. Swimming, though, is not as effective as other types of exercise because your weight is mostly supported by the water.

If appropriate, reforming your vices can also lower the risk of osteoporosis. Moderating alcohol and caffeine intake and quitting smoking will help your bones as well as the rest of your body.

Other possibilities for the actual treatment of osteoporosis are currently under investigation. Calcitonin, a hormone made by cells within the thyroid gland, enhances calcium deposition in bone; a synthetic version (Calcimar) has been approved for treating osteoporosis. As of this writing, however, evidence that it prevents fractures is limited to a single study. Drawbacks include its cost and the need to administer it by injection. A nasal spray preparation is being developed.

Sodium fluoride, administered by mouth in large doses, has undergone extensive study as a treatment for osteoporosis. Bone density does increase but some experts believe that fluoride bone may not be as strong as normal bone. The prevention of fractures has yet to be demonstrated.

Preventing and treating osteoporosis is clearly more complex than ads for calcium products suggest. If you believe you’re in a high-risk category, talk to your physician. If you’ve already reached menopause, an evaluation of risk factors will indicate whether estrogen therapy or simpler measures are right for you.

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