As a fourteen year veteran of the fitness industry, I have been telling others, for years, to exercise to increase bone density. The reason for increasing bone density is to help avoid developing the bone thinning disease, osteoporosis. This fact is stated over and over in numerous fitness articles, exercise text books, and other reading materials I receive regularly. However, none of the articles I have read, to date, have gone into depth on what exactly happens in your bones and body that causes osteoporosis. As a fitness instructor trainer and professional, I felt I needed to know more about this disease. I set out to learn all I could about osteoporosis. What I learned was shocking and disturbing.

Once thought to be an inevitable part of growing old, having brittle bones, and doing what I call the "Curly Shuffle" (the bent over, hunch-backed shuffle gait displayed by of some of the elderly) does not have to come with old age at all and can be prevented. The bent over, hunch-backed appearance called "Dowager's Hump" or "kyphosis," is due to compression fractures (caused by osteoporosis) in the vertebrae (bones) that make up your spine. The "Curly Shuffle" that often accompanies the Dowager's Hump, is due, mainly, to the sheer terror many of the elderly have of falling, that could possibly cause a debilitating fracture.

According to the National Osteoporosis Foundation (NOF), osteoporosis is a major public health threat for 28 million Americans, 80% of whom are women. In the US, 10 million individuals already have the disease, and 18.5 million more have low bone mass, putting them at increased risk for developing osteoporosis. As many as 1 out of 2 women over age 50, will suffer from a fracture due to osteoporosis. Men and women suffering just from broken hips alone, total some 300,000 per year. Fifty thousand of these individuals with a broken hip will die, directly resulting from complications with surgery to repair the fracture, or from becoming bedridden and unable to move around (NOF 1-2).

Known as the "silent disease" or "silent thief," osteoporosis has no symptoms since you cannot feel your bones becoming weak and brittle (NOF). Unfortunately for some, they find out they have the disease when a bone breaks. Therefore, finding out how strong your bones are and taking preventive measures against developing osteoporosis, are key.

These facts were shocking to me. I had no idea of the vast scope of this disease. To find out that almost 1 out of 2 women will be affected by the disease, is a very disturbing fact. What was even more disturbing to me is that being involved in a health related field, I did not know these things. Therefore, I can only guess that many others have no information regarding the seriousness of this disease (including many in the fitness industry).

"Osteo" refers to bone, as "porosis" refers to porous, thus, osteoporosis means, in a literal sense, "porous bone." Porous bones result from the reduction in the overall quantity of bone tissue, caused when the rate of bone resorption (breaking down of old bone) exceeds the rate of new bone being made (formation) (Seeley 176). This loss of tissue, meaning mass or density of the bone itself, leaves the bone brittle (porous), and weakened to the point that, just by sneezing or coughing, can cause a fracture. Osteoporosis is the cause of 1.5 million fractures each year in the hip, spine, wrist, and other bones (NOF 2).

What causes osteoporosis? Several factors are involved. Women, in particular, are more susceptible to the disease, due to having smaller, less dense bones than men (NOF 4). Also, the female hormone, estrogen, helps to regulate the rate of bone resorption (although, at this time, it is not fully understood how) (Weksler 2). Therefore, declining levels of estrogen in pre-menopausal and menopausal women, put women at a much greater risk of developing osteoporosis. This fact seems to be the main cause of the disease in women over age 50 (Rizzoli 2). This does not mean, however, women over 50 will inevitably develop osteoporosis.

The NOF includes these other risk factors involved in developing osteoporosis (besides being female):

• being tall, (a woman over 5'6'') or having a thin, small boned frame
• advanced age (bone loss increases with age)
• a family history of osteoporosis
• early menopause
• abnormal absence of menstrual periods (amenorrhea)
• anorexia nervosa or bulimia (eating disorders - starvation and binge/purge)
• low dietary calcium intake
• using certain medications (steroids, thyroid medication, anticonvulsants, and some others. For more information on these medications, the NOF has a publication called, "Medications & Bone Loss.")
• a sedentary lifestyle
• smoking
• excessive alcohol consumption
• malabsorption problems

Bone is living tissue within our bodies. According to Seeley, Stevens, and Tate, there are 206 bones that make up the skeletal system which performs the following functions:

• Provides support: Strong, healthy bones are the major supporting and weight bearing tissue of the body.
• Provides protection: Surrounding various organs in the body, bone is hard and provides protection for these soft tissues. Some examples are the brain, being encased by the skull, and protected by the rib cage are vital organs, the heart, and the lungs.
• Produces movement: Skeletal muscles are attached to the bones by tendons (strong bands of fibrous connective tissue). When skeletal muscles contract, they move the bones they are attached to, causing the body to move.
• Provides storage: Bone stores minerals, from the blood, the principal ones are calcium and phosphorus. Should the levels of these become low, the bone releases some of the minerals back into the blood. Bone cavities also store fat, that, if needed, is released into the blood as a source of energy for other tissues.
• Produces red blood cells: Located in cavities inside "spongy or cancellous" bone, is red bone marrow, which produces red blood cells and platelets (Seeley 155).

Bone consists of bone matrix (matrix - to surround or contain within), which is non-living, extracellular (outside the cells) material, that is responsible for the characteristics of bone (Seeley 159). Its' composition consists of collagen, for flexible strength, and minerals, mainly calcium, for compression strength, similar to concrete (159). Bone cells produce the matrix, maintain it, and break down old matrix and replace it with new.

When we think of our bones and picture them, it is usually as the hard, dry skeletons we see hanging around each year at Halloween. But as one can see by its' many functions, bone is very much living tissue that is extremely necessary to the lively-hood of our bodies.

There are three categories of bone cells, each having a different function, as discussed by Seeley (159-161). Osteoblasts remove calcium from the blood to form the mineralized bone matrix. This is known as ossification. The osteoblasts join together, similar to holding hands, and the matrix surrounds them. Parathyroid hormone (PTH), produced by the parathyroid glands that are embedded in the back part of each lobe of the thyroid gland, is the major regulator of blood calcium levels (173). Osteoblasts are receptive to messages sent from PTH signaling that calcium levels are low in the blood, and they then give out signals to other cells that release calcium into the blood (173-174).

Once the matrix surrounds the cells, osteoblasts are trapped inside the matrix and then become mature bone cells, known as osteocytes (Seeley 160). The osteocytes form a mold around which the matrix, in cylindrical or circular layers, forms an "osteon." The osteon includes a canal with blood vessels, osteocytes and the bone matrix surrounding it (163).

Osteoclasts are the cells responsible for bone "resorption," the breaking down of old bone (matrix). In the process called remodeling, old bone is replaced by new bone (NOF 3). Remodeling converts woven bone (newly replaced bone from a fracture site) into mature bone, known as lamellar bone, is responsible for bone growth, repair, and change in shape of bone, as well as the adjustment of bone to stress ( Seeley 169-170).

Osteoclasts break down bone and release calcium into the blood. These are the cells that were alerted by the osteoblasts, after they were affected by PTH signaling that more calcium was needed for bone formation (Seeley 173-174). Opposed to this, a secretion produced by the thyroid gland, calcitonin, inhibits the osteoclast activity when there is too much calcium in the blood (175).

Your bones increase in density up until approximately age thirty. At this point, density remains constant or begins to decline at the rate of 1% per year (NOF 2). What occurs to a person's bones when they have osteoporosis is the rate of bone resorption (breaking down) exceeds the rate of bone formation (new bone) (Seeley 176). This results in a loss of bone tissue, density, and mass, leading to a fragile, weak, and frail lattice-work of bone, extremely susceptible to fracturing.

So, now I know what causes osteoporosis and who is mainly at risk - women. Working in the fitness industry, as a fitness instructor trainer/certifier, 90 percent of the people I provide programs for are women. In this industry, the disease, osteoporosis, is mentioned often, and almost casually it seems (to me - now), as just another reason to make sure we all exercise. After learning all this amazing and startling information, I now, will definitely address this disease in more depth, to the women in my programs, so they will then understand the seriousness of osteoporosis.

Exercising and eating right, meaning a low-fat diet rich in calcium, play the largest role in the prevention of osteoporosis. Calcium is important in developing and maintaining bone. Therefore, getting adequate calcium in the diet, is a concern, especially for women, who are more susceptible to developing osteoporosis than men.

Please note, that calcium alone will not prevent osteoporosis, but will help as one part of taking preventative action against developing the disease. The NOF recommends the following calcium intakes for adults:
Women
25-49 years - (premenopausal) - 1,000 mg/day
50-64 years - (postmenopausal, taking estrogen) - 1,000 mg/day
50-64 years - (postmenopausal, not taking estrogen) - 1,500 mg/day
65+ years - 1,500 mg/day
Men
25-64 years - 1,000 mg/day
65+ years - 1,500 mg/day

If you are concerned about your calcium intake, you should speak to your doctor or dietitian about this. One or both of these professionals can explain what foods are calcium rich besides low-fat dairy products, and will be able to tell if you are getting enough calcium in your diet. Should you need to use a supplement, your doctor can also recommend which one is best for you, and which type of supplement is most readily absorbed.

Vitamin D is important in order for the body to be able to absorb calcium in the intestine (Seeley 173). Calcium must be absorbed adaquately in the body in order to ensure proper bone formation. This is the reason for most milk being Vitamin D fortified. Vitamin D is produced in the skin from exposure to sunlight. Sources conflict on the amounts of Vitamin D that are required daily. They ranged from 200 IU (International Units) to 800 IU. The most popular recommendation seemed to be 400 IU per day for adults. Keep in mind that milk has Vitamin D added, most calcium, and other supplements also have Vitamin D included. High doses of Vitamin D are not recommended as they can be harmful. Again, consult with your doctor or dietitian regarding your intake of Vitamin D.

Weight bearing exercise, such as walking, running, sports, weight training, aerobic dance, etc. is extremely important in preventing osteoporosis. As described by Seeley, mechanical stress applied to bone, such as in weight bearing exercise (swimming is not considered weight bearing, although an excellent exercise), osteoblast (bone forming) activity increases, and when the stress is removed, osteoblast activity decreases. However, osteoclast (resorption) activity continues at a nearly normal rate (170). This shows the importance of exercise in increasing bone density and, also shows what happens without activity, such as being bedridden for long periods or having a sedentary lifestyle.

As discussed earlier, menopause, a transition in women's bodies where levels of estrogen drop, is the major cause of the disease in women over age 50. Women should discuss with their doctor the possibilities of prescribing estrogen (the hormone that helps to regulate the rate of bone resorption) replacement therapy (ERT) or other options regarding prevention of osteoporosis. If you feel you are at risk for developing osteoporosis, speak with your doctor regarding a bone mineral density test (BMD). This is done several ways, but the most accurate devise, suggested by the NOF, is a Dual Energy X-ray Absorptiometry (DXA or DEXA). This device can scan the whole body, as opposed to others that can only scan the wrist, spine or heel. This test by a DEXA, uses little radiation, is painless and takes 10-20 minutes. Results of your bone density are determined by a comparative analysis with bone density of someone your age, with healthy bones, and the density of someone's bone at peak bone mass.

Osteoporosis is a serious disease that affects millions, but does not have to. Prevention of this disease, and many others, is just as important (if not more important) than finding a cure. Taking preventive measures including: exercising, eating a healthy diet rich in calcium, not smoking, and keeping in touch with your doctor regarding osteoporosis (especially menopausal women, or others with several risk factors), are definite ways that you can avoid developing this debilitating disease.

WORKS CITIED
How Strong Are Your Bones? Washington, D.C. National Osteoporosis Foundation, 1994 (Revised 1997).

Rizzoli, Rene, and Jean-Philipe Bonjour. "Hormones and Bones." Lancet (March 2, 1997): 4p. Online. Internet. 22 April 1998.

Seeley, Rod R., Trent D. Stevens, and Philip Tate. Anatomy and Physiology Fourth Edition. Boston: McGraw-Hill Companies, 1998.

Weksler, Marc E. "Osteoporosis: Up-to-Date Stratagies For Prevention and Treatment." Geriatrics Vol 52, Issue 1 (April 1997): 5p. Online. Internet. 22 April 1998.

Copyright 1998 Sabrina Ellen Svard