Osteoporosis

Osteoporosis is a progressive disease of the skeletal system in which bones become so brittle that they break more easily than they should. According to the World Health Organization, this disease is characterized by a combination of two factors:

• Low bone mass, often referred to as low bone mineral density
• A “micro-architectural deterioration of bone tissue” that affects its structural quality

While this definition makes it clear that osteoporosis is not simply the consequence of low bone mass, there is no diagnostic test to assess bone’s structural quality. As such, osteoporosis is currently diagnosed and defined based on low bone mineral density (BMD) only.

There is no “cure” for osteoporosis, but there are measures you can take to prevent its onset or reverse its course—no matter what age you are—because bones continue to be renewed throughout life.

How Do Bones Change Over Time?

Although you can’t feel it happening, your bones are constantly undergoing a process called bone remodeling. Old and damaged bone tissue is continuously being cleared away (bone resorption) and replaced with healthy, new tissue (bone formation). As we age, our bodies become less efficient at constructing new bone, leading to a gradual but cumulative loss of bone strength.

Bone remodeling occurs in both the tough, outer core, which is high in minerals and the spongy, inner core, which is rich in marrow and blood vessels. Just as in home remodeling, quality materials (nutrients) and effective labor (cells involved in bone remodeling) produce the best results.

Exercise is also critical because it targets which bones are remodeled and how. Demands placed on certain bones trigger extra remodeling, so that limbs under repetitive stress, such as a pitcher’s throwing arm, become thicker and stronger over time. Weight-bearing exercise also engages muscles, which push and tug against bones, stimulating the growth of new bone tissue.

Bones continue to grow more dense and thick until peak bone mass is reached, which for most people is typically sometime in their early twenties. However, what is “peak” bone mass for one person may be very different than that of another. There are significant differences in the average peak bone mass between the sexes, and across races, ethnic groups and even people living in different geographical areas within the same country.

In most healthy people, the rate of bone formation keeps up with bone resorption until their late thirties or early forties, at which time the balance
shifts and bone “demolition” begins to outpace “construction” of new bone. At first, this shift is subtle and results in minimal bone loss. For women, bone loss accelerates at menopause due to declining levels of estrogen and other hormones essential to bone health. Genetics, hormones, exercise, nutrition, and other lifestyle factors all influence how dense our bones become and remain throughout life.

Why Do Bones Fracture?

Bone is living tissue with complex nutritional needs. New bone is formed by an interlocking matrix of the protein collagen, which is “cemented” into place by a mix of minerals. Calcium phosphate and calcium carbonate predominate in this mix, but it also includes magnesium and trace minerals, which are micronutrients found in extraordinarily small amounts in the body, yet are essential for many body functions including bone health.

Old or damaged bone is demolished (resorbed) by chemicals that dissolve the minerals and disrupt the collagen matrix. When the bone remodeling process favors demolition, bones become more porous (less dense). If the integrity of the protein collagen matrix is also compromised, bones become increasingly weak and brittle and are no longer capable of efficiently repairing the microscopic fractures that result from mild trauma.

Some bones are more fragile than others, to begin with. The vertebrae, pelvis, hip, wrist, flat bones, and the ends of long bones are a more porous, honeycomb-like bone that is highly sensitive to metabolic changes. These bones are also the most susceptible to loss of density and structural integrity as we age.

The geometry of the wrist, hip and spine also make them extremely susceptible to breakage. In the spine, vertebrae may collapse from the stress of the body’s own weight or from light lifting. Most wrist and hip fractures result from falls. In fact, the key risk factors for fracture revolve around an older person’s greater propensity to fall. Falls are often associated with the common effects of aging, including poor eyesight, reduced muscle strength and coordination, and/or mental confusion due to medications or dementia.

How Is Osteoporosis Diagnosed?

In most people, osteoporosis is a silent thief of the body’s structural support system. However, sometimes there are visible warning signs such as:

• Partially visible tooth sockets, resulting from deterioration of the jawbone and receding gums (the origin of the phrase “long in the tooth”)
• Translucent skin on the back of the hands and prematurely gray hair (due to poor vitamin D metabolism)
• Loss of height stooped posture or kyphosis—the hunchback posture characterized by progressive loss of muscle tone and vertebral crush fractures (known colloquially as “the dowager’s hump”)
• Arthritis-like pain in the bones and joints

Without any of these visible warning signs, the only way to “see” the porous bone that is the hallmark of osteoporosis is to perform a biopsy, which is impractical. The most common method of testing for osteoporosis is Dual Energy X-ray Absorptiometry (DEXA or DXA), which measures BMD via x-rays, usually of the hip or spine. The “normal” reference value is the peak bone mass of a healthy, 20-year-old Caucasian woman. A BMD measurement significantly below this peak value results in a diagnosis of osteoporosis. Osteopenia, or being at risk for osteoporosis, is the diagnosis for those with scores slightly below “normal.” Unfortunately, these diagnostic criteria do not account for either the natural biological variation that occurs or for normal age-related bone loss. “This means that unless women maintain their bone mass at peak levels throughout their life span, they will be labeled as at-risk or diseased,” points out Gillian Sanson, author of The Myth of Osteoporosis.

In addition, there are well-known issues with the accuracy of DXA machines because there are no international standards for their calibration. Using the same DXA machine for repeat tests is recommended to accurately detect changes in BMD over time. Despite these concerns, DXA measurement remains the leading diagnostic test for osteoporosis; and most research, treatment, and prevention efforts focus on increasing BMD.

Some practitioners prefer to screen for osteoporosis in lower-risk patients using lower radiation BMD methods, such as single-photon absorptiometry (SPA) of the wrist, which has proven effective in predicting spinal bone density. Another option for low risk patients is measuring BMD in the heel using SPA or ultrasound.

For a more complete picture of bone health, some practitioners may also request a urine test that measures biochemical markers released during the bone remodeling process. Whereas it may take years to show changes in BMD, repeated urine testing over just a few months can help identify if there is an increase or decrease in bone breakdown. This provides more immediate feedback on whether or not lifestyle changes or treatments are working to improve bone health.

Does Low Bone Density Cause Fractures?

Having low BMD does not cause fractures, but it is one of many risk factors. A low BMD score has not been shown to accurately identify which women will fracture as they age. Many people who fracture do not have osteoporosis and many people with osteoporosis never fracture. According to Sanson, the vast majority of the population will never fracture as a result of low bone density.

Who Is At Greatest Risk?

The chances of developing osteoporosis goes up with every year of life and some of the risk factors are beyond our control. For example, women are at greater risk than men because they typically have smaller, less dense bones. Caucasian women usually have greater bone loss than African American and Hispanic women. Yet, Asian women tend to have lower bone mass than Caucasian women but suffer fewer osteoporotic fractures, which tells us it is not strictly a matter of bone mineral density. Genetics, diet, nutrition, hormone balance, and other factors also play a role in bone health.

The following lifestyle choices, which are within our control, are associated with bone loss:

• Smoking contributes to poor metabolism and is also believed to cause women to enter menopause earlier, putting them at risk earlier.
• High alcohol intake limits the stomach’s ability to produce hydrochloric acid, which is necessary for the absorption of calcium and magnesium; when magnesium is lost in the urine, it takes calcium with it.
• Caffeine is a diuretic that also contributes to a high rate of calcium excretion for several hours after consumption.
• Salt consumption also contributes to calcium excretion because it affects the calcium-magnesium ratio. Some people are very sensitive to salt and will excrete excess amounts of calcium even on a diet with a moderate salt intake.
• Soft drinks, such as colas or soda pop (with or without caffeine) contain high levels of phosphoric acid. Consuming several servings per day disrupts the calcium-phosphorus balance, causing calcium to be leached from the bones and lost in the urine. Soft drinks with caffeine have an even higher rate of calcium excretion.
• Sugar consumption contributes to calcium depletion because it hinders calcium absorption and increases calcium excretion.
• Lack of exercise, especially weight-bearing exercise, accelerates bone loss.

Although osteoporosis most often develops as a result of the aging process, in some cases it can be triggered by another illness or use of certain medications. In particular, the following treatments are associated with increased bone loss:

• Anticoagulants, such as warfarin (Coumadin) or heparin, are used for treating heart disease to reduce the risk of heart attacks and strokes, as well as to reduce blood clots in people undergoing or recovering from surgery. Anticoagulants work by reducing the effects of vitamin K, which helps calcium bind to bone tissue.
• Anticonvulsants, a class of drugs for treating epilepsy, are now also widely used for treating mood disorders such as bipolar disorder, as well as fibromyalgia, and nerve pain. Examples include carbamazepine (Tegretol) and pregabalin (Lyrica). These drugs interfere with vitamin D metabolism, reducing the body’s ability to absorb calcium and leading to bone loss.
• Anti-anxiety medications, such as clonazepam (Klonopin), diazepam (Valium), and lorazepam (Ativan), also inhibit vitamin D metabolism, leading to bone loss.
• Aromatase inhibitors are drugs used to treat breast and ovarian cancer in postmenopausal women. They work by disrupting the production of estrogens, which leads to accelerated bone loss as a side-effect of cancer treatment.
• Corticosteroids are used for chronic conditions such as rheumatoid arthritis, asthma, lung disease, and inflammatory bowel disease. In particular, corticosteroid drugs such as prednisone, prednisolone, and dexamethasone are very damaging to the bone, as they both reduce the body’s ability to absorb calcium and speed up bone resorption.
• Diuretics are prescribed for high blood pressure, congestive heart failure, liver disease, and kidney disease to increase urination to reduce fluid throughout the body. Some diuretics, such as the commonly prescribed furosemide (Lasix), cause the kidneys to excrete more calcium, which can lead to bone loss.
• Immunosuppressants stifle the body’s immune system reaction after a graft or organ transplant. They are also used to treat psoriasis, Crohn’s disease, and other autoimmune diseases. However, they also hinder the formation of new bone.
• Kidney dialysis solutions and many antacids contain aluminum, which disrupts the calcium-phosphorus balance necessary for bone formation, thereby contributing to bone loss. Other acid reflux drugs, such as Prilosec, Prevacid and Nexium for treating gastroesophageal reflux disease (GERD) and heartburn, reduce the acid in the stomach, thereby interfering with calcium absorption and contributing to bone loss.
• Dr. Irwin Goldstein, director of The Institute for Sexual Medicine cautions that oral contraceptives may have a negative long-term effect on bone health. Oral contraceptives elevate sex hormone-binding globulin (SHBG) levels, and those elevated levels persist even after the pills are stopped. Osteoporosis may develop as a result of impaired androgen activity due to the elevated SHBG levels.

How Does Nutrition Affect Bone Health?

Calcium balance is so important that the human body has evolved several mechanisms to compensate for fluctuations in diet, intestinal absorption, and excretion. For example, people with a low-calcium diet will have higher levels of calcitriol (a form of vitamin D) in their blood to improve calcium absorption.

However, contrary to popular belief, most Americans don’t have trouble getting enough calcium from their diets, but they do have trouble effectively absorbing calcium. Vitamin and mineral deficiencies, which are increasingly common as we age, inhibit our ability to make use of calcium to build bone. Nutrients that are known to affect bone health include:

• Vitamin A helps control the bone remodeling process to keep formation and resorption in sync. With a deficiency, bone cells form faster than the old ones can be resorbed, causing abnormal and sometimes painful bone formations.
• Vitamin B6 is necessary for the production of hydrochloric acid, which is essential for calcium absorption.
• Vitamin C helps to produce collagen for new bone formation, as well as for linking together some of the proteins that provide bone structure.
• Vitamin D (which actually gets converted to a hormone in the body) works in concert with other hormones and minerals to tightly control the amount of calcium that circulates in our blood. Without vitamin D, calcium cannot be absorbed and deposited into bone tissue. Vitamin D maintains the proper balance between calcium and phosphorus to build and maintain healthy bones.
• Vitamin K is required for the production of osteocalcin, a protein prevalent in the bone that facilitates calcium crystallization and provides structure during bone formation.
• Magnesium plays a key role in calcium metabolism and must be maintained in balance with calcium. When magnesium is in short supply, calcium does not make its way to the bones but instead collects in other parts of the body, where it can cause painful conditions such as kidney stones, gallstones, and gout.
• Manganese stimulates the production of protein-like molecules that provide a structure for calcification to take place.
• Phosphorus also requires a delicate balance with calcium to promote bone health. Too much or too little both contribute to osteoporosis, but having too much is more common. With too much phosphorus, calcium is leached from other parts of the body to maintain a phosphorus-calcium balance. With too little phosphorus, calcium is deposited outside the bone, collecting elsewhere in the body.
• Protein is essential for the collagen in our bones, but too much may promote bone loss. In Preventing and Reversing Osteoporosis, Alan M. Gaby, MD, explains that an excess of protein causes more calcium to be excreted in the urine, as a result of calcium leaching from the bones to buffer the acidic breakdown of protein. High phosphorus levels also result, as it is a byproduct of protein metabolism.
• Strontium (the stable form, not the radioactive form) promotes bone growth by enhancing calcium absorption, reducing bone turnover, and building high-quality bone tissue. Strontium has chemical properties similar to calcium and has been found to replace calcium in some biochemical processes, including bone remodeling.
• Trace minerals are also essential for bone health, including but not limited to
  • Boron, which is necessary to activate vitamin D
  • Silicon, which is necessary for the collagen protein mix during the initial stages of bone formation and also contributes to bone mineralization
  • Zinc and copper, which need to be balanced, and are believed to stimulate bone formation.

Another major digestive factor that affects nutrition is stomach secretions, specifically hydrochloric acid, which is necessary for the breakdown of foods so nutrients can be absorbed. As we age, the cells in our stomach lining produce less hydrochloric acid, hampering the absorption of nutrients such as calcium and the other vitamins and minerals essential for bone health.

Most stomach problems stem from too little digestive acid, instead of too much. However, many people reach for over-the-counter antacids to treat stomach upset, not realizing that these antacids block the action of hydrochloric acid, further aggravating the source of the stomach pain, and contributing even more to osteoporosis by blocking calcium absorption.

Digestive disorders such as celiac disease and Crohn’s disease, as well as eating disorders like anorexia also interfere with nutrient absorption.

How Do Hormones Affect Bone Health?

Hormones are important players in bone remodeling throughout life, especially sex hormones. Abrupt declines in sex hormones produce rapid bone loss in both men and women. For example, women who have a hysterectomy, especially younger women, are at high risk of osteoporosis, while men with low testosterone, at any age, are far more likely to suffer fractures.

The estrogen hormones promote bone health primarily by inhibiting bone resorption. After menopause (and its accompanying decrease in estrogen levels), the bone turnover rate accelerates leading to more rapid bone loss, which is one reason estrogen therapy is so often recommended. However, estrogen coupled with progesterone provides added benefits for bone health because progesterone stimulates bone formation and contributes to bone strength, typically resulting in a significant net gain in the bone.

Women who experience rapid bone loss are typically deficient in both estrogen and testosterone, which is believed to stimulate bone formation, increase calcium absorption, and increase bone’s ability to retain calcium. It is clear that combined sex hormones play an important role in maintaining bone health.

DHEA (dehydroepiandrosterone) contributes to bone health in a variety of ways. It binds to estrogen receptors to block the resorption effects of estrogen; it increases progesterone levels, aiding bone formation; and it works with testosterone to stimulate bone formation and calcium absorption. It appears to be the only hormone that is capable of both inhibiting bone resorption and stimulating bone formation. It is also a precursor hormone that can be converted by the body into other hormones, including estrogen and testosterone. So, not only does it have direct effects on bone remodeling, but it also increases the levels of other major hormones that affect bone health.

Calcitonin and parathyroid hormone (PTH) are two hormones that work together to “manage” calcium levels. When calcium is ingested, some is absorbed into the bloodstream, and some is stored in bone. If blood calcium levels are low, PTH signals the bones to release calcium. This is in opposition to calcitonin, which acts to reduce calcium in the blood and is a potent inhibitor of bone resorption.

Thyroid hormone influences the bone remodeling process. Because the thyroid hormone boosts the energy of all cells in the body, it speeds up both bone resorption and formation. Too little thyroid hormone stunts growth in children, while too much can weaken the skeleton because bone resorption occurs faster than formation.

Cortisol, produced in the adrenal gland, also has complex effects on bone and needs to be in balance. Small amounts are necessary for healthy bone development, but large amounts serve to block bone formation, leading to bone loss and a very high risk of fracture. Therefore, stress is detrimental to bone health, just as it is to other parts of the body because it leads to an excess of cortisol.

Human growth hormone (HGH) is believed to promote bone health by boosting bone formation, although studies show mixed results. Proponents say growth hormone resorbs more bone in the first 12 to 18 months and then acts to build bone, eventually raising bone mineral density over a longer period of time.

Even oxytocin often referred to as the “cuddle hormone,” is believed to play a role in bone health, with recent research demonstrating a relationship between low oxytocin levels and severe osteoporosis.

Can Medications Prevent Fracture?

Osteoporosis medications may benefit those with a high risk of fracture, but concerns exist about their side effects and long-term safety. Individuals at different ages are likely to come to different conclusions about whether the benefits outweigh the risks.

The most common treatment for osteoporosis is currently a class of powerful, anti-resorptive drugs known as bisphosphonates, including Fosamax and Actonel, which bind calcium to bone tissue. While they do increase bone mineral density and appear to reduce the risk of vertebral, hip, and other fractures in the short term (five or fewer years), they may have long-term effects that may not be reversible. For this reason, Sanson argues that the risk of treatment for younger women is likely to dwarf the benefits.

Bone biopsies of women who suffered fragility fractures while on Fosamax show that bone formation is nearly 100 times slower. By suppressing bone turnover, bisphosphonates seem to reduce the bone’s ability to bend under pressure without breaking. In other words, bisphosphonates may not build bone so much as harden it. If the high risk of fracture justifies this treatment, exercise can boost effectiveness by promoting bone renewal.

Recently, bisphosphonates have been linked to a few negative outcomes, including:

• Osteonecrosis of the jaw (ONJ) or “jaw death,” which develops when bone tissue in the jaw fails to heal after mild trauma, such as a tooth extraction. Patients taking bisphosphonates should inform their dentist before undergoing procedures.
• Esophageal cancer, which is not surprising considering that irritation of the upper gastrointestinal (GI) tract is a major complaint of oral bisphosphonate users.
• Adverse effects on heart function, including a higher risk of developing atrial fibrillation, a form of heart arrhythmia, which can lead to serious consequences, including stroke.

Alternatives to bisphosphonates have shown limited effectiveness in preventing fractures, or lack of reliable proof of safety.

Conclusion

It’s never too late—or too early—to work on optimizing bone health. Preventing osteoporosis and bone fracture requires paying attention to multiple facets of bone health including:

• Maintaining a well-balanced diet, including vitamin and mineral supplements, as needed.
• Facilitating the absorption and metabolism of calcium and other nutrients
• Preventing the loss of calcium and other essential bone nutrients
• Minimizing interference with the bone remodeling process
• Maintaining hormone balance throughout life’s stages
• Engaging in a lifelong fitness plan that includes weight-bearing exercises.
• Exercise is the single most important action you can take to promote healthy bones. Vigorous, weight-bearing exercise stimulates bone renewal and increases bone density, at any age.