Osteoporosis

Introduction

Osteoporosis is a disease of the skeleton in which bones become brittle and prone to fracture. In other words, the bone loses density. Osteoporosis is diagnosed when bone density has decreased to the point where fractures occur with mild stress.

Until a healthy person is around age 40, the process of breaking down and building up bone by cells called osteoclasts and osteoblasts is a nearly perfectly coupled system, with one phase stimulating the other. As a person ages, or in the presence of certain conditions, this system breaks down and the two processes become out of sync. The reasons why this occurs during aging are not clear. Some individuals have a very high turnover rate of bone, some have a very gradual turnover, but the breakdown of bone eventually overtakes the build-up.

The Bones

The Function of Bones. The skeleton has a dual function:

It provides structural support for muscles and organs.
It also serves as a depot for the body’s calcium and other essential minerals, such as phosphorus and magnesium.

The skeleton holds 99% of the body’s calcium. The remaining 1% circulates in the blood and is essential for crucial bodily functions, ranging from muscle contraction to nerve function to blood clotting.

Bone Turnover: the Breakdown and Growth of Bones. Like other organs in the body, bone tissue is constantly being broken down and reformed again. This turnover is necessary for growth, for repair of minor damage that occurs from everyday stress, and for the maintenance of a properly functioning body. Two essential cells are involved in this process:

Osteoblast cells are produced by bone cells and are the bone builders. They rebuild the skeleton, first by filling in the holes with collagen, and then by laying down crystals of calcium and phosphorus.
Osteoclast cells are formed from certain blood cells and are responsible for the breakdown, or resorption, of the skeleton. These cells dig holes into the bone and release the small amounts of calcium into the bloodstream that are necessary for other vital functions.

Each year, about 10 - 30% of the adult skeleton is remodeled in this way. The bone build up (formation)-break down (resorption) balance is controlled by a complex mix of hormones and chemical factors. If bone resorption occurs at a greater rate than bone build up, your bone loses density and puts you at risk for osteoporosis.

In women, estrogen loss after menopause is associated with rapid resorption and loss of bone density. This group, then, is at highest risk for osteoporosis and therefore for fracture.

Primary Osteoporosis

There are two primary kinds of osteoporosis: type I and type II:

Type I. Type I, or high turnover, osteoporosis occurs in 5 - 20% of women, most often between the ages of 50 and 75. This is because of the sudden postmenopausal decrease in estrogen levels, which results in a rapid depletion of calcium from the skeleton. This is associated with fractures that occur when the vertebrae compress together, causing a collapse of the spine. It is also associated with fractures of the hip, wrist, or forearm caused by falls or minor accidents. Women have a higher risk for type 1 osteoporosis than men.
Type II. Type II, or low turnover, osteoporosis (also known as age-related or senile osteoporosis) results when the process of resorption and formation of bone are no longer coordinated, and bone breakdown overcomes bone building. (This occurs with age in everyone to some degree.) Type II osteoporosis affects both men and women and is primarily associated with leg and spinal fractures. Older women can have both type I and type II osteoporosis.

What determines the existence of osteoporosis, whether type I or type II, is the amount of calcium left in the skeleton and whether it places a person at risk for fracture. Someone who has exceptionally dense bones to begin with will probably never lose enough calcium to reach the point where osteoporosis occurs, whereas a person who has low bone density could easily develop osteoporosis despite losing only a relatively small amount of calcium.

Secondary Osteoporosis

Secondary osteoporosis is caused by other conditions, such as hormonal imbalances, diseases, or medications (such as corticosteroids or anti-seizure drugs).

Causes

Because the patterns of reforming and resorbing bone often vary from patient to patient, experts believe several different factors account for this problem. Important chemicals (such as estrogen, parathyroid hormone, and vitamin D) and blood factors that affect cell growth are involved with this process. Changes in levels of any of these factors could play a role in the development of osteoporosis.

The Role of Sex Hormones in Bone Breakdown

Although ordinarily associated with women, sex hormones play a role in osteoporosis in both genders, most likely by controlling the birth and duration of life of both osteoclasts (bone breakers) and osteoblasts (bone builders).

Women and Estrogen. Experts are still puzzled by the rapid decline in bone density after menopause, when a woman’s ovaries stop producing estrogen. Estrogen comes in several forms:

The most potent form of estrogen is estradiol. Estradiol deficiency appears to be a very strong factor in the development of osteoporosis.
The other important but less powerful estrogens are estrone and estriol.

The ovaries produce most of the estrogen in the body, but it can also be formed in other tissues, such as body fat, skin, and muscle. After menopause, some amounts of estrogen continue to be manufactured in the peripheral body fat. Even though the ovaries have stopped producing estrogens directly, they continue to be a source of the male hormone testosterone, which converts into estradiol.

Estrogen may have an impact on bone density in various ways:

Estrogen’s most important effect on osteoporosis appears to be prevention of bone breakdown (resorption). Some research suggests that estrogen may control the life span of osteoclasts, the cells responsible for bone breakdown.
One study reported that part of estrogen’s beneficial actions may involve maintaining normal levels of vitamin D, an important nutrient in bone protection.

Men and Androgens and Estrogen. In men, the most important androgen (male hormone) is testosterone, which is produced in the testes. Other androgens are produced in the adrenal glands. Androgens are converted to estrogen in various parts of a man’s body, including bone.

Studies have suggested that the loss of estrogen as well as testosterone may contribute to bone loss in elderly men. In one study, elderly men were first given a drug that blocked their normal hormones and then were given estrogen and testosterone patches. When the estrogen patch was removed, the bone breakdown process accelerated. When both patches were removed, the number of the bone-building cells (the osteoblasts) decreased. In other words, both hormones appeared to be integral to bone function in men.

Vitamin D and Parathyroid Hormone Imbalances

Low levels of vitamin D and high levels of parathyroid hormone (PTH) are associated with hip fracture in women after menopause:

Vitamin D is a vitamin with hormone-like properties. It is essential for the absorption of calcium into the bone and for normal bone growth. Lower levels result in impaired calcium absorption, which in turn causes an increase in PTH.
Parathyroid hormone (PTH) is produced by the parathyroid glands. These are four small glands located on the surface of the thyroid gland. They are the most important regulators of calcium levels in the blood. When calcium levels are low, the glands secrete more PTH, which then increases blood calcium levels. High persistent levels of PTH stimulate bone resorption (bone loss).

Genetic Factors

Several studies on family members, including twins, have strongly suggested that genetic factors help determine bone density. Some examples include the following:

Of particular interest are genetic factors that affect vitamin D, a critical nutrient for calcium absorption in the body.
Many studies are looking at abnormalities in genes that may cause deficiencies in estrogen receptors, molecules that help estrogen work on cells. Estrogen is important in maintaining bone density in both men and women.

Causes of Secondary Osteoporosis

Corticosteroids. More than 30 million Americans have disorders that are commonly treated using corticosteroid drugs (also called glucocorticoids or steroids). Oral corticosteroids can reduce bone mass in both men and women. It is not clear whether inhaled steroids carry the same risks, but some studies indicate that they may cause bone loss when taken at higher doses for long periods of time. (Children on inhaled steroids may have temporary impaired growth, but they do not appear to be at risk for bone loss.)

Antidepressants. Selective serotonin reuptake inhibitors (SSRIs) -- a class of antidepressants that includes fluoxetine (Prozac), paroxetine (Paxil), and sertraline (Zoloft) -- may be associated with bone loss in both older men and women, according to two 2007 studies in the Archives of Internal Medicine. The researchers did not find an increased risk for bone loss with other types of antidepressants.

Diuretics. Diuretics, which are used to treat high blood pressure, have different effects on osteoporosis, depending on the type. Loop diuretics, such as furosemide (Lasix), increase the kidneys’ excretion of calcium, which can lead to thinning bones. Thiazide diuretics, on the other hand, protect against bone loss, but this protective effect ends after use is discontinued.

Contraceptives. Hormonal contraceptives that use progestin without estrogen (such as Depo-Provera injection or other progestin-based contraceptives), can cause loss of bone density. For this reason, the Food and Drug Administration (FDA) recommends that Depo-Provera injections should not be used for longer than 2 years. Some, but not all, studies suggest that combination estrogen-progestin oral contraceptives increase the risk for osteoporosis later in life. Women who take birth control pills should be sure to get adequate calcium and vitamin D from diet or supplements.

Other Medications. Anti-epileptic (anti-seizure) drugs increase the risk for bone loss (as does epilepsy itself). Other drugs that increase the risk for bone loss include the blood-thinning drug heparin, and hormonal drugs that suppress estrogen (such as gonadotropin-releasing hormone agonists). A 2006 study in the Journal of the American Medical Association suggested that long-term (greater than 1 year) use of proton-pump inhibitors (PPIs) may increase the risk for hip fractures. PPIs are used to treat gastroesophageal reflux disease (heartburn) and include omeprazole (Prilosec), lansoprazole (Prevacid), and esomeprazole (Nexium).

Predisposing Medical Conditions. Osteoporosis can be secondary to several other conditions, including alcoholism, diabetes, hyperthyroidism, epilepsy, chronic liver or kidney disease, celiac disease, scurvy, rheumatoid arthritis, leukemia, cirrhosis, gastrointestinal diseases, vitamin D deficiency, hypogonadism (impaired development of reproductive organs), lymphoma, hyperparathyroidism, and rare genetic disorders such as Marfan and Ehlers-Danlos syndrome.

Risk Factors

Gender. An estimated 10 million adults in the United States have osteoporosis and another 34 million have low bone mass that places them at risk for developing osteoporosis. A 2004 report from the Surgeon General's office estimates that by 2020, half of all Americans over age 50 could be at risk for this condition. Eighty percent of people with osteoporosis are women. Men start with higher bone density and lose calcium at a slower rate than women, which is why their risk is far lower. Nevertheless, after age 50, bone loss increases and, according to recent studies, more rapidly than previously thought.

Ethnicity. Although adults from all ethnic groups are susceptible to developing osteoporosis, Caucasian and Asian women and men face a comparatively greater risk. About 20% of non-Hispanic white and Asian women older than age 50 have osteoporosis, and over 50% are at risk due to low bone mass. Osteoporosis affects 10% of Hispanic women (49% at risk) and 5% of non-Hispanic black women (35% at risk). Body type can also be a factor. Osteoporosis is more common in women who have a small, thin body frame and bone structure.

Specific Risk Factors for Estrogen Deficiency and Low Bone Density in Women

Events associated with estrogen deficiencies are the primary risk factors for osteoporosis in women.

Natural and Surgical Causes of Estrogen Deficiency.

Menopause. Within 5 years after menopause, the risk for fracture increases dramatically. Fractures occurring during this period are more likely to occur in the wrist or spine than the hip, but their occurrence is a strong predictor of later severe osteoporosis and hip fracture.
Surgical removal of ovaries.
Missing periods for 3 months or longer.
Never giving birth.
Pregnancy and nursing do not increase the risk for osteoporosis even though during those times calcium is diverted from the mother to the baby. A factor believed to be associated with reduced bone density is elevated at a constant level during nursing, but as the baby is weaned, levels of the factor decline and bone formation is restored.

Female Athlete Triad. In athletes, excessive exercise plays a major role in many cases of anorexia (and, to a lesser degree, bulimia), which in turn increases the risk for low estrogen levels and bone loss. The term "female athlete triad" in fact, is now a common and serious disorder facing young female athletes and dancers and describes the combined presence of the following problems:

Osteoporosis
Amenorrhea (absence or irregular menstruation)
Eating disorders

Specific Risk Factors for Bone Density Loss in Men

Some specific risk factors in men include:

Hormonal deficiencies, including both testosterone and estrogen, which occur in older men (although much more slowly than in women). Estrogen deficiencies may also play a major role in osteoporosis in older men. It is unknown yet what normal estrogen levels are in men.
Medical conditions that can reduce testosterone levels, such as prostate cancer treatments, testicular surgery, and mumps.
Hypogonadism, which is a severe deficiency in the primary hormone that signals the process leading to the release of testosterone and other important reproductive hormones.

Of concern, are studies suggesting that men who have osteoporosis and suffer hip fractures are far less likely to be tested and treated for low bone density than are women. In one study, only 27% of men were treated for osteoporosis compared to 71% of women.

Risk Factors for Bone Density Loss in Both Men and Women

Dietary Factors. Diet plays an important role in preventing and speeding up bone loss in men and women. Calcium and vitamin D deficiencies, of course, are important factors in the risk for osteoporosis. Other dietary factors may also be harmful or protective for certain people.

Lack of Exercise. Lack of exercise can put thinner people at risk for osteoporosis.

Being Underweight. Being underweight is a risk factor for osteoporosis in men as well as women. (Shortness, thinness, and narrow hips all increase the risk for fracture in people with low bone density.)

Lack of Sunlight. The photochemical effect of sunlight on the skin is a primary source for vitamin D. Bone formation peaks in the summer and bone breakdown increases in the winter. People who avoid sun exposure to prevent skin cancer may be at risk for vitamin D deficiency, particularly it they are elderly.

Smoking. Women who smoke, particularly after menopause, have a significantly greater chance of spine and hip fractures than those who don’t smoke. Men who smoke also have lower bone density.

Diabetes. Diabetes changes bone quality and density and increases the risk for osteoporosis, but the effects differ depending on type:

Type 1 diabetes is associated with a slightly reduced bone density, putting patients at risk for osteoporosis and possibly fracture.
Type 2 diabetes, on the other hand, is associated with an increased bone density. In such cases, the bone quality itself may be impaired, since people with type 2 diabetes are still at higher risk for fractures.

Older patients with any diabetes type are at high risk for falling, which compounds the risk for fracture.

Risk Factors in Children and Adolescents

The maximum density that bones achieved during the growing years is a major factor in whether a person goes on to develop osteoporosis. Persons, usually women, who never develop peak bone mass in early life are at high risk for osteoporosis later on. Children at risk for low peak bone mass include children who are:

Born prematurely
Have anorexia nervosa (more common in girls)
Young, highly competitive athletes
Take oral corticosteroid drugs (inhaled steroids, which are common in asthma treatments, appear to pose a very low risk or none at all)
Have certain medical conditions (cystic fibrosis, epilepsy, inflammatory bowel disease, and celiac disease)
Have delayed puberty

Although to a large extent genetics predict bone health, exercise and good nutrition during the first three decades of life (when peak bone mass is reached) are still excellent safeguards against osteoporosis (and countless other health problems).

Diagnosis

About 20 - 30% of Caucasian women in the U.S. can expect to be affected by osteoporosis, including having a spinal fracture, after age 60. Hispanic, Asian, and Native American women have an even higher risk. Nearly all of them are unaware of the condition and so fail to seek a diagnosis. Even worse, studies continue to report inadequate evaluation for osteoporosis even after a fracture.

Candidates for Bone Density Screening or Testing

Evidence suggests that screening for osteoporosis can help prevent fractures. Expert groups now recommend bone density screening for the following people:

All women over age 65.
Any postmenopausal women under 65 years with risk factors for osteoporosis (being thin, being a smoker, having a family history of osteoporosis, corticosteroids use, or any serious high-risk condition, such as hyperthyroidism or early menopause).
Any older men or women who suffer a fracture. (Unfortunately, studies suggest that only a minority of these patients are evaluated and treated for osteoporosis. Men are especially less likely to be tested.)

Whether perimenopausal women should be screened is unclear. (Perimenopause is the period that extends a few years before and after menopause, usually ages 50 - 59.) Some experts believe that women as young as 21 who have strong risk factors for osteoporosis (such as anorexia or absence of menstruation due to over-exercising) should consider being tested. It is also important that older women continue to get bone density tests. A 2006 study found that only 10% of women over age 75 receive bone density screenings, even though they are the age group most likely to have hip fractures.

Techniques Used for Measuring Bone Density

Bone Densitometry. The standard technique for determining bone density is a form of bone densitometry called dual-energy x-ray absorptiometry (DEXA). DEXA is simple and painless and takes 2 - 4 minutes. The machine measures bone density by detecting the extent to which bones absorb photons that are generated by very low-level x-rays. (Photons are atomic particles with no charge.) Measurements of bone mineral density are generally given as the average concentrations of calcium in areas that are scanned.

Bone mineral density is usually measured at the hip rather than the spine or wrist, which appears to be the most predictive of hip fracture. (Hip fractures are the most dangerous fractures, particularly in women older than sixty.) The bone density in the spine may also be measured. (Spinal bone density in older people however may be misleading. Bone density in this group may increase because of compression on the spinal bones from arthritic changes in the spine. Therefore, bone density measurements may be normal or even high, but the patient may actually be at risk for fracture.)

Ultrasound. Ultrasound techniques measure bone density in the heels, fingers, and leg bones. In early studies, advanced ultrasound techniques, such as quantitative ultrasound (QUS), are promising for improving accuracy in predicting fractures when used with DEXA. Ultrasound itself is less expensive than DEXA and uses no radiation. Ultrasound bone tests are sometimes given at health fairs or other non-medical settings. It should be noted that these results typically vary widely from measurements of the hipbone and are not reliable when used alone.

Quantitative Computed Tomography. Quantitative computed tomography (QCT) scans, a form of CT scans, can provide highly detailed information about spinal density. Radiation doses from this technique are higher than the others. Whether QCT predicts fracture risk accurately is, however, unknown.

Determining Osteoporosis and the Risk for Fracture

Osteoporosis is diagnosed when bone density has decreased to the point where fractures will happen with mild stress, the so-called fracture threshold. This is determined by measuring bone density and comparing the results with the norm. However, low scores on bone density are not very accurate in determining fracture risk without consideration of other risk factors for fracture.

In general, doctors take the following steps to determine osteoporosis:

Bone mineral density ) is measured, typically in the hipbone, using bone densitometry.
Measurements of bone mineral density are given as mg/cm.² This is the average concentration of bone mineral in the areas that are being scanned. In general, bone is normal if results are greater than 833 mg/cm.² Low bone density (osteopenia) is between 833 and 648 mg/cm.² Osteoporosis is diagnosed with results below 648 mg/cm.²

These measurements still do not always indicate the true risk for fracture. The doctor also assesses risk factors and other considerations. The next step is to compare the patient's bone mineral density to normal bone density, which is defined as the average bone mineral density in the hipbones of premenopausal Caucasian women. (This group is used as the basis for the norm because of their high risk and greater proportion in the American population.)

The health professional then uses this comparison to determine her standard deviation (SD) from this norm. Standard deviation results are given as Z and T scores:

A T score gives the standard deviation of the patient in relationship to the norm in young adults. Doctors often use the T-score and other risk factors to determine the risk for fracture.
A Z score gives the standard deviation of the patient in relationship to the norm in her own age group. Z scores may be used to monitor the effects of treatments in women who have been diagnosed with osteoporosis.

For example, the lifetime risks for a younger woman with a specific T-score would be higher than the same scores in an older woman because the younger woman would have a longer time to lose bone density. In general, the T scores in a 55-year-old woman suggest the following degrees of risk for hip fracture.

One standard deviation or less below the norm indicates normal bone mineral density. (This carries a lifetime chance for a hip fracture of up to about 20%, depending on age and other risk factors.)
Between 1 and 2.5 standard deviation s below normal defines osteopenia, which is low bone density. This carries between a 20 - 50% lifetime risk for fracture.
More than 2.5 standard deviation s predicts osteoporosis and over a 60% chance for hip fracture. Additional risk factors increase the risk. They include low weight, smoking, risks for falling, and especially a history of previous fractures. For example, in women 65 years old with low bone density but no adverse factors, the risk for fracture is 4.3% in 1 year and 28.6% over 5 years. In similar women with a previous fracture, the probability of fracture at 1 year is 11% and at 5 years is 71.8%.

Not all older women with osteoporosis develop fractures. There is some evidence that the body partially compensates after menopause by increasing bone strength, which can help offset the risk for fracture. Techniques to measure bone strength may better identify women at higher or lower risk.

Note: Because the standards are based on Caucasian women, they do not necessarily apply to men, children, or to non-Caucasian women. For example, men have a lower risk for fracture at the same standard deviations as women. Researchers are attempting to establish risk guidelines for these groups as well.

Laboratory Tests

Laboratory blood or urine tests for identifying certain markers of bone loss may prove to be useful in certain cases:

High levels of the chemicals deoxypyridinoline and C-telopeptide in the blood may indicate increased risk for hip fracture. These substances are produced when bone is broken down.
A urine test detecting a substance called N-telopeptide may indicate bone loss (although it is not associated with any risk for fracture).

Lifestyle Changes

Because osteoporosis affects such a considerable portion of the female population, total prevention may not be possible, particularly for high-risk groups. Once a woman goes through menopause and more rapid bone depletion occurs, the line between prevention and treatment blurs. Despite their lower risk for osteoporosis, men should also protect their bones with the same healthy lifestyle habits.

Exercise

Exercise is very important for slowing the progression of osteoporosis. Although mild exercise does not protect bones, moderate exercise (more than 3 days a week for more than a total of 90 minutes a week) reduces the risk for osteoporosis and fracture in both older men and women. Everyone who is in good health should aim for more. Exercise should be regular and life-long. Before beginning any strenuous exercise program, older patients, those at risk or those who have serious medical conditions, should talk to their doctors.

Specific exercises may be better than others, depending on the age group:

Children should begin exercising before adolescence, since bone mass increases during puberty and reaches its peak between ages 20 and 30. Some evidence suggests that exercise may help develop bone mass in teenagers more effectively than high calcium intake. High-intensity exercises may be particularly bone-strengthening in young people. (Such regimes should not be confused with the athlete-triad -- intense competitive exercise, eating disorders, and menstrual irregularities -- that causes osteoporosis in young athletes.)
Weight-bearing exercise applies tension to muscle and bone and, in young people, encourages the body to compensate for the added stress, increasing bone density by as much as 2 - 8% a year. In premenopausal women these exercises are very protective. (Young men need high-intensity exercises to increase bone mass.) Careful weight training is also very beneficial for elderly people, especially women.
Regular brisk long walks improve bone density and mobility and may relieve osteoarthritic pain. High-impact exercises can be very bone-protective in young and middle-aged adults who have no precluding medical or physical conditions. Most older individuals should avoid high-impact aerobic exercises (step aerobics), which increase the risk for osteoporotic fractures. (Older people, particularly women who engage in jumping exercises should do so under supervision.) Although low-impact aerobic exercises such as swimming and bicycling do not increase bone density, they are excellent for cardiovascular fitness and should be part of a regular regimen.
Exercises specifically targeted to strengthen the back help prevent fractures later on in life and can be beneficial in improving posture and reducing kyphosis (hunchback), even in people with existing severe conditions.
Low-impact exercises that improve concentration, balance, and strength, particularly yoga and tai chi, have been found to decrease the risk of falling. In one study, tai chi reduced the risk of falling by almost half.

Calcium Supplements

In 2007, the Food and Drug Administration (FDA) proposed a new health claim for foods and dietary supplements that contain calcium and vitamin D. The FDA’s recommendation will allow manufacturers of these products to state that the combination of calcium and vitamin D can reduce the risk of osteoporosis. Also in 2007, the National Osteoporosis Foundation (NOF) updated its recommendations for getting enough calcium and vitamin D3. The NOF now recommends 1,200 mg of calcium/day and 800 - 1,200 I.U. of vitamin D3/day for adults age 50 and older. (For strong bones, people need enough of both calcium and vitamin D.)

For years, doctors have recommended that women take supplements of calcium plus vitamin D to help maintain bone density and reduce the risk for fractures. Many studies, including a 2007 review in the Lancet, show that a combination of calcium and vitamin D can help prevent osteoporosis. However, a 2006 New England Journal of Medicine study raised some questions about this approach. In the Women’s Health Initiative study, women were randomly assigned to receive either 1,000 mg of calcium carbonate plus 400 IU of vitamin D a day or placebo. The results indicated that daily calcium and vitamin D supplements:

Improve slightly (by 1%) hip bone density
Prevent hip fracture, but only for women who consistently take the supplements. (Another 2006 study supported this finding.)
Do not prevent spine or other types of fractures
Produce a slight increase in the risk of kidney stones

The medical community has differing views on how to interpret these findings. Some doctors recommend that women over age 60 should still consider taking calcium and vitamin D for bone health. Other doctors feel that due to the risks of kidney stones, supplements are beneficial only for women (especially those over age 70) who do not get enough calcium in their diets. Ask your doctor whether or not you should take calcium supplements.

Appropriate Daily Doses. Recommended daily amounts of calcium depend on age and risk factors:

In young people, children ages 3 - 8 should take 800 mg of calcium per day, while children and adolescents ages 9 - 17 need 1,300 mg per day. Teenage girls who do not have enough calcium in their diets should consider taking supplements, which can help build bone density during these critical years.
The standard recommended dose for people over age 50 is about 1,200 mg per day, but actual dosage may be higher or lower depending on risk factors. Even doses of 1,000 mg may help preserve bone in many postmenopausal women without osteoporosis, including during winter months (when bone loss is greatest). In women who have already experienced osteoporosis-related fractures, however, 1,000 mg daily may not add any protective benefits without bone-building medication.
Some experts suggest that all pregnant women, adolescents, and those on corticosteroids take 1,000 - 1,300 mg of calcium every day.
Breast-feeding women should have 2,000 mg per day.

Forms of Calcium Supplements. There are several different kinds of calcium supplements, such as calcium carbonate (Caltrate, Os-Cal, Tums), calcium citrate (Citracal), calcium gluconate, and calcium lactate. Although each kind provides calcium, they all have different calcium concentrations, absorption capabilities, and other actions. Their value in preserving bones depends on many different factors:

Calcium Concentrations. Forty percent of calcium carbonate is actually calcium, whereas calcium citrate is 24% calcium, and calcium gluconate is only 9% calcium.
Calcium Absorption Capabilities. The calcium must also be absorbed from the stomach into the bloodstream. Calcium citrate is better absorbed than many other calcium compounds. It was reported to be the first calcium supplement to preserve bone density after menopause. (Calcium citrate also increases iron absorption. Milk and other calcium compounds tend to reduce iron absorption.) One simple method for testing the absorbency of a particular brand of calcium tablet is to place it in a glass of white vinegar at full strength and check to be sure that it breaks up within 30 minutes. Taking large amounts of antacids can impair calcium absorption. People should take calcium supplements after meals.

Side Effects. Calcium supplements, even at normal doses of about 1,000 mg a day, can increase the risk for kidney stones. People should be careful not to exceed the upper limit of 2,500 mg per day. (Because many commercial foods are now fortified with calcium, this upper limit may be easier to reach than people think.) Calcium may boost the effects of drugs used to treat osteoporosis.

Although not a specific side effect of calcium, there has been much public concern about reports of a small amount of lead in calcium supplements. Although exposure to high levels of lead can cause health problems, the amount in such supplements is very small and may pose little or no hazard.

Vitamin D and Other Vitamins

Vitamin D. Vitamin D helps the stomach and the gastrointestinal tract absorb calcium. It also is the essential companion to calcium in maintaining strong bones. Moreover, vitamin D protects against osteoporosis only in combination with calcium.

Vitamin D is made in the skin using energy from the ultraviolet rays in sunlight. People also can get it from dietary supplements.

As a person ages, vitamin D levels decline. They also fall during winter months and when people have inadequate sunlight. Pollution may also contribute to less sunlight and declining vitamin D levels.

Most current adult guidelines recommend:

400 IU (10 mcg) for people aged 50 - 60.
600 IU (15 mcg) for those over age 70 who do not have sufficient exposure to sunlight. (Evidence suggests that higher doses of vitamin D -- up to 1,000 IU per day -- may help prevent fractures in people with osteoporosis.)

There are various recommendations for daily vitamin D intake. In 2007, the National Osteoporosis Foundation updated its guidelines to recommend 400 - 800 IU of vitamin D3 for adults younger than age 50, and 800 - 1,000 IU of vitamin D3 for adults age 50 and older. Vitamin D3, also called cholecalciferol, is the form of vitamin D that is best for bone health. In addition to supplements, food sources for vitamin D3 include fortified milk, egg yolks, saltwater fish, and liver.

In 2007, the U.S. National Institute of Health’s Office of Dietary Supplements released a report regarding vitamin D and bone health. Researchers were not able to definitely separate the effect of vitamin D from that of calcium, as most clinical trials evaluate the combination of these supplements. The report did indicate that a combination of daily vitamin D3 (700 - 800 IU) and calcium (500 - 1,200 mg) decreases the risks of falls, fractures, and bone loss in elderly people (ages 62 - 85 years).

Sufficient sunlight exposure and drinking milk fortified with vitamin D supply most people’s normal needs for vitamin D. One cup of whole milk provides about 100 IU of vitamin D.

Vitamin D is toxic in doses above 2,000 IU a day. No one should exceed the recommended daily intake of vitamin D except under the direction of a doctor.

Many people could become deficient in vitamin D as they avoid sunlight to prevent skin cancers and instead increase their intake of milk products, such as yogurt and skim milk, which may have little vitamin D. Such individuals may need to take supplements. People with darker skin have a higher risk for vitamin D deficiency than those with lighter skin.

Vitamin D derivatives are being investigated for treating osteoporosis. Calcitriol (Calcijex, Rocaltrol), for example, is a prescription-form of vitamin D that can increase bone mass and decrease the rate of spinal fractures. However, calcitriol increases the risk for high blood calcium levels (hypercalcemia) and requires frequent monitoring.

Vitamin K. Vitamin K has properties that protect bone and prevent fracture. Because intestinal bacteria produce vitamin K, and the vitamin is found in leafy vegetables, deficiencies are rare. Some evidence suggests, however, that people may not be consuming enough of this nutrient. Vitamin K affects blood clotting, and taking supplements is not recommended without first talking to a doctor. Vitamin K2 (menatetrenone), a form of vitamin K, may help prevent fractures in people with osteoporosis.

Vitamin B12. Studies suggest that people need the right amounts of vitamin B12 and folic acid to maintain their bone mineral density.

Vitamin A. High amounts of dietary vitamin A reduce bone density and may even increase the risk for fracture in postmenopausal women. (A form of vitamin A, retinoic acid, has been found to stimulate bone breakdown.)

Dietary Recommendations

The DASH Diet and Low Sodium. Perhaps a good general approach for people at risk for osteoporosis (or almost any adult) is the DASH diet plus sodium (salt) restriction. The DASH (Dietary Approaches to Stop Hypertension) diet is used to help people with hypertension maintain healthy blood pressures. A 2003 study also reported that it might help protect bones and improve cholesterol levels. This diet not only is rich in important nutrients and fiber but also includes foods that contain far more potassium, calcium, and magnesium, than are found in the average American diet. All of these minerals are important for bone protection. The dietary recommendations are as follows:

Avoid saturated fat (although include calcium-rich dairy products that are no- or low-fat). When choosing fats, select monounsaturated oils, such as olive or canola oils. These fats are also found in some fish. Although no one wants to be overweight, even a slight excess of fat helps protect bones. In one study, women who ate more fat in their diet were, on average, better able to absorb calcium than were women who had been put on a low-fat, high-fiber diet.
Choose whole grains over white flour or pasta products. Include nuts, seeds, or legumes (dried beans or peas) daily.
Choose fresh fruits and vegetables every day. Many of these foods are rich in potassium, magnesium, and other minerals that are important for bone (as well as heart) protection.
Choose protein preferably from fish, poultry, or soy products. Soy in combination with fiber-rich foods or supplements may have specific benefits. Oily fish may also be particularly beneficial. They contain omega-3 fatty acids, which have been associated with heart and nerve protection.

Salt Restriction. Reducing salt may protect both the heart and the bones. High sodium intake interferes with calcium retention. Note: Fast foods and commercial snacks are usually high in sodium and have been linked with weak bones.

Dairy Products and Calcium-Rich Foods. Although some studies have reported that dairy products benefit the bones, it is not entirely clear if high-calcium diets reduce the risk for fractures compared to adequate intake of vitamin D. Until more is known, people should be sure their diets have sufficient calcium. Dietary calcium is available from many good sources.

Milk and Dairy Products. The best source of calcium in the diet is from milk fortified with vitamin D. Four glasses of milk provide about 1,200 mg of calcium. (Skim milk and yogurt products, unfortunately, are often low in vitamin D, which is important for calcium absorption.) According to a 2003 study, girls who have low milk intake increase their risk for fracture in adulthood. One report even suggests that milk proteins actually slow bone break down. It is not clear, however, if drinking milk after menopause offers any significant bone protection.
Other Calcium-Rich Foods. Other calcium-rich foods include shrimp, canned salmon or sardines, black strap molasses, calcium-fortified tofu, and almonds. A number of commercial foods, including orange juice and some cereals, are now calcium fortified. Dark green vegetables (broccoli, kale, turnip greens) are rich in calcium but little of it is absorbed (kale is best).

Mineral-Rich Fruits and Vegetables.

Potassium. Potassium may be very important for strong bones and may help counteract negative effects of high-protein diets. Potassium-rich fruits include bananas, oranges, prunes, and cantaloupes, and vegetables that contain potassium include carrots, spinach, celery, alfalfa, mushrooms, lima beans, potatoes, avocados, and broccoli.
Magnesium. Some studies have observed that low levels of magnesium may contribute to thinning bones. Some studies suggest that magnesium supplements help suppress the cycle that leads to bone loss. Experts recommend 350 mg a day for supplements. However, excessive magnesium may be harmful in people with diabetes or kidney disease. Foods rich in magnesium include dairy products, spinach, potatoes, beets, nuts, sole, and halibut.
Other Minerals. Phosphorous, boron, and zinc have also been associated with bone protection.

Protein. Protein may be important for frail older people for improving muscle strength. Researchers, meanwhile, have associated both low and high protein intake with bone loss. Protein deficiencies appear to trigger hormonal changes that increase bone breakdown. On the other hand, high protein intake increases urinary calcium loss, which can impair bone density in people with low-calcium diets. High-protein diets, however, do not appear to cause bone loss if calcium intake is also high. The bottom line is to eat enough protein but to balance it with plenty of calcium-rich, and other mineral-rich, foods.

The protein source (meat, soy, or fish) may have some effect on bone density, although the effects are not clear. Studies are mixed on whether protein from meat has a positive or negative effect on bone loss. In any case, the best sources of protein for bone protection may be from oily fish or soy.

Choosing protein from fish (especially oily fish such as sardines, salmon, mackerel, fresh tuna, and herring) is a good option. Oily fish are high in vitamin D, which is bone protective. Such fish are also heart protective. Wild salmon has a much higher vitamin D content than farmed salmon. American brands of canned tuna, meanwhile, generally do not contain significant amounts of vitamin D.
Soy may have some modest protection against bone loss. Soy is high in estrogen-like plant chemicals called isoflavones, which may improve bone health in older women. In particular, the isoflavone genistein is being studied for its effects on bone health. A small 2007 study indicated that genistein supplements, when taken with vitamin D and calcium, may help improve bone density in postmenopausal women with thinning bones. (However, other studies indicate that soy has no effect on bone density in healthy premenopausal women.) Soy food products that also contain calcium, such as tofu, may be particularly beneficial. In such cases, 3 ounces of tofu supply 60% of daily calcium requirements.

Alcohol. Alcohol has different effects on bones depending on how much is consumed. One study found that women older than age 65 who drank one to two drinks (1 - 2 oz) of alcohol weekly had higher bone density than non-drinkers. Alcohol in moderate amounts may reduce parathyroid hormone and increase estrogen levels. Excessive drinking, however, has been associated with brittle bones.

Cola, Coffee, Tea and Caffeine. One study suggested that drinking tea regularly may help protect bones. Nevertheless, there has been some concern that caffeine consumption, particularly from coffee, may increase calcium levels in urine and reduce levels in the body. In one trial, consumption of lots of coffee (9 or more cups per day) was associated with an increased risk of hip fractures in women, but not in men. However, not all studies support a risk. Some evidence suggests that caffeine may pose a danger for bone loss only in elderly thin women -- but not in those who have normal or high weight. Drinking carbonated beverages, particularly cola, may increase the risk for bone fractures in people with low bone density.

Quit Smoking

Everyone who smokes should quit. The risk for osteoporosis from smoking appears to diminish after quitting.

Preventing Falls and Fractures

An important component in reducing the risk for fractures is preventing falls. Risk factors for falling include:

Slow walking
Inability to walk in a straight line
Certain medications (such as tranquilizers and sleeping pills)
Low blood pressure when rising in the morning
Poor vision

Recommendations for preventing falls or fractures from falls in elderly people include:

Exercise to maintain strength and balance if there are no conflicting medical conditions. In one study of older people, this was the single best intervention for preventing falls.
Do not use loose rugs on the floors.
Move any obstructions to walking, such as loose cords or very low pieces of furniture, away from traveled areas.
Rooms should be well lit.
Have regular eye checkups.
Try wearing hip pads. Hip pads are specially designed to protect hipbones against falls and are worn under clothing. Evidence on their protection against fractures is weak, however, particularly since compliance is poor. Nevertheless, newer hip pads that are thinner and made with newer materials may be helpful and more appealing.
Wear thinner, hard-soled shoes. Studies indicate these shoes are just as comfortable as the popular resilient-soled footwear, but they may be difficult to find. Soft-soled high-resilient so-called athletic footwear may contribute to impaired balance and dangerous falls, in part, because these cushioned shoes offer less stability.

Medications

Many drugs are available to treat osteoporosis. Unfortunately, studies continue to report that doctors fail to evaluate and adequately treat both men and women for this condition, even after a fracture. According to one study of women over age 60, fewer than 2% were evaluated for osteoporosis or spinal fracture by their doctors. Among those who were diagnosed, only 36% received appropriate medication. Among adults who had sustained fractures, less than 5% of men and fewer than half of women were evaluated and treated according to recommended guidelines, indicated two other studies. In one of the studies, only 24% of women received treatment for osteoporosis after a fracture. In both studies, the older a woman was, the less likely she was to have adequate evaluation or treatment.

Drugs Used to Treat Osteoporosis. Two types of drugs are used to treat osteoporosis:

Antiresorptive Drugs. Antiresorptives include bisphosphonates, hormone replacement therapy, selective estrogen-receptor modulators (SERMs), and calcitonin. Bisphosphonates are the standard drugs used for osteoporosis. These drugs block resorption (preventing bone break down), which slows the rate of bone remodeling, but they cannot rebuild bone. Because resorption and reformation occur naturally as a continuous process, blocking resorption may eventually also reduce bone formation.
Anabolic, or Bone-Forming, Drugs. Drugs that rebuild bone are known as anabolics. The primary anabolic drug is low-dose parathyroid hormone (PTH), which is administered through injections. This medicine is proving to be very effective in restoring bone and preventing fractions. PTH is still relatively new, and long-term effects are still unknown. Fluoride is another bone-building drug, but it has limitations and is not commonly used.

Both types of drugs are effective in preventing bone loss and fractures, although they vary in their effectiveness and safety.

Bisphosphonates

Bisphosphonates are antiresorptive drugs. They are the primary drugs for preventing and treating osteoporosis. They can help reduce the risk of both spinal and hip fractures, including among patients with prior bone breaks.

Studies indicate that these drugs are effective and safe for at least 10 years. Eventually, however, bone loss continues with bisphosphonates. This may be due to the fact that bone breakdown is one of two phases in a continuous process of rebuilding bone. Over time, just blocking resorption will interrupt this process and impair the second half of the process -- bone formation. Some researchers think that this problem may be overcome by building bone for a couple of years with parathyroid hormone (PTH), then following this treatment with bisphosphonates to prevent the breakdown of bone. (Administering the two drugs simultaneously is not effective because bisphosphonates interfere with the way PTH works.)

A 2006 study of the bisphosphonate alendronate (Fosamax), the most widely used osteoporosis drug, indicated that women at low risk for fracture may be able to stop using the drug after 5 years without increasing their fracture risk for another 5 years. However, the Journal of the American Medical Association study also suggested that it is safer for women at high risk for spine fractures to keep taking alendronate on a continuous basis.

Candidates. National Osteoporosis Foundation guidelines recommend that the following people should take or consider bisphosphonates:

Women with a below-normal bone density of 2.5 standard deviation or greater and no history of fractures
Women with below-normal bone density 1 standard deviation or more and a history of fractures

Brands. Bisphosphonates are available in different forms:

Oral bisphosphonates. These pills include alendronate (Fosamax), risedronate (Actonel), and ibandronate (Boniva). Alendronate and risedronate are taken once a week. In 2005, ibandronate was approved as the first once-monthly pill. Risedronate is also available in a pill that contains calcium. Risedronate and alendronate are approved for both men and women.
Injectable bisphosphonates. In 2007, zoledronic acid (Reclast) was approved as the first once-yearly injection treatment for osteoporosis. The injectable form of ibandronate (Boniva), approved in 2006, requires injections 4 times a year. Injectable bisphosphonates are an alternative for patients who may have difficulty swallowing pills or sitting upright after oral bisphosphonate treatment.

Side Effects. The most distressing side effects of bisphosphonates are gastrointestinal problems, particularly stomach cramps and heartburn. These symptoms are very common and occur in nearly half of all patients. Other side effects may include irritation of the esophagus (the tube that connects the mouth to the stomach) and ulcers in the esophagus or stomach. Some patients may experience muscle and joint pain. To avoid stomach problems, doctors recommend:

Take the pill on an empty stomach in the morning with 6 - 8 ounces of water (not juice or carbonated or mineral water).
After taking the pill, remain in an upright position. Do not eat or drink for at least 30 - 60 minutes. (Check your drug’s dosing instructions for exact time.)
If you develop chest pain, heartburn, or difficulty swallowing, stop taking the drug and see your doctor.

Osteonecrosis (bone death) of the jaw is a rare side effect that has occurred mainly in patients who received intravenous bisphosphonates for cancer treatment (not osteoporosis). Many of these patients had major dental procedures before developing osteonecrosis. However, this bone decay condition has also been reported in some patients who have taken bisphosphonates by mouth (mainly alendronate). Symptoms may include jaw pain or swelling, gum infections, and poor healing of the gums. Talk to your doctor or dentist if you experience any jaw or gum discomfort while taking a bisphosphonate drug.

SERMs

Raloxifene (Evista) belongs to a class of drugs called selective estrogen-receptor modulators (SERMs). These drugs are similar, but not identical, to estrogen. Raloxifene provides the bone benefits of estrogen without increasing the risks for estrogen-related breast and uterine cancers. Raloxifene was approved in 1997 to prevent osteoporosis in postmenopausal women, and in 1999 for the treatment of osteoporosis in postmenopausal women. In 2007, the Food and Drug Administration approved raloxifene for prevention of breast cancer in postmenopausal women with osteoporosis, as well as postmenopausal women at high risk for invasive breast cancer.

While there are many SERM drugs, raloxifene is the only one approved for both treatment and prevention of osteoporosis. Only postmenopausal women who have or are at risk for osteoporosis should take this drug. Studies indicate that raloxifene can stop the thinning of bone and help build better quality and stronger bone.

Side Effects. Raloxifene increases the risk for blood clots in the veins. Because of this side effect, raloxifene also increases the risk for stroke (but not other types of heart disease). These side effects, though rare, are very serious. Women should not take this drug if they have a history of blood clots, or if they have certain risk factors for stroke and heart disease. More common mild side effects include hot flashes and leg cramps.

Calcitonin

Produced by the thyroid gland, natural calcitonin regulates calcium levels by inhibiting the osteoclastic activity, the breakdown of bone. The drug version is derived from salmon and is available as a nasal spray (Miacalcin) and an injected form (Calcimar). Calcitonin is not used to prevent osteoporosis. It treats osteoporosis. It may be effective for spinal protection (but not hip) in both men and women. Calcitonin may be an alternative for patients who cannot take a bisphosphonate or SERM. It also appears to help relieve bone pain associated with established osteoporosis and fracture.

Side Effects. Side effects include headache, dizziness, anorexia, diarrhea, skin rashes, and edema (swelling). The most common adverse effect experienced with the injection is nausea, with or without vomiting. This occurs less often with the nasal spray. The nasal spray may cause nosebleeds, sinusitis, and inflammation of the membranes in the nose. Also, many people who take calcitonin develop resistance or allergic reactions after long-term use.

Parathyroid Hormone

Although high persistent levels of parathyroid hormone (PTH) can cause osteoporosis, daily injections of low and intermittent doses of this hormone actually stimulate bone production and increase bone mineral density. In clinical studies, teriparatide (Forteo), a drug made from selected amino acids found in parathyroid hormone, reduced the risk for spinal and non-spinal fractures by 50 - 65%. It may prove to be a very useful drug for men with osteoporosis. Unlike most treatments for osteoporosis, including bisphosphonates, the benefits may persist even after the injections have been stopped.

Although the treatment requires injections, researchers are investigating a nasal spray version of PTH. In addition to easing patient discomfort, there is some preliminary evidence that nasal-administered PTH may be better absorbed than injections. Side effects of PTH are generally mild and include nausea, dizziness, and leg cramps. No significant complications have been reported to date.

Early animal studies did report bone tumors in mice that were given parathyroid long-term. Such effects have not been observed in humans to date. However, people with Paget disease, (a disorder in which bone thickens but also, oddly, weakens), should not take parathyroid hormone, since they are at higher than normal risk for bone tumors.

Hormone Replacement Therapy

Hormone replacement therapy (HRT) is sometimes used to prevent osteoporosis. A Women’s Health Initiative (WHI) study found that women who received estrogen, or estrogen plus progestin, therapy had fewer fractures than women who received placebo.

However, WHI studies have also shown that estrogen increases the risk for breast cancer, blood clots, strokes, and heart attacks. For this reason, women need to balance the benefits that HRT has on bone-loss protection, with the risks it carries for other serious health conditions. The Food and Drug Administration recommends that women first try other medications for prevention of osteoporosis.

HRT is available in many different forms, including pills and skin patches. [See In-Depth Report #40: Menopause.]

Investigational Drugs

New SERMs. Bazedoxifene (Viviant) is a new selective estrogen receptor modulator (SERM) that is in phase III clinical trials. In research presented at the 2007 annual meeting of the American Society for Bone and Mineral Research (ASBMR), bazedoxifene reduced new cases of non-spine fracture by 52% compared to placebo.
Biologic Drugs. Denosumab is a humanized monoclonal antibody injectable drug currently in phase III studies. It targets the RANK ligand, a protein involved with cells that break down bone (osteoclasts). Results presented at the 2007 ASBMR meeting indicated that denosumab may help increase bone mineral density by as much as 10.6%. Odanacatib is another biologic drug showing promise in phase IIB trials. Odanacatib inhibits cathepsin K, a protein that also plays a role in osteoclast activity.
Strontium. Strontium, a chemical element found in bone, may help increase bone formation and decrease bone resorption. NB S101 is a strontium drug currently in phase II trials.