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July 2001
Vol. 10, No. 07,
pp 53–54, 56.
 
 
 
Health Perspectives
Densities and mysteries

Beyond milk: How to optimize bone health and minimize osteoporosis risk

opening art
DIGITAL VISION
Virginia Shook is a milk-drinking woman from her days growing up on a Midwest farm. So she was surprised when a fall during an exercise class broke both wrists. “They were very bad breaks because my bones were soft. I had osteoporosis and didn’t know it,” she says. Apparently her high calcium intake wasn’t enough. Then there’s the Wisconsin man who took a 20-mg dose of prednisone daily for 20 years—yet a bone scan showed normal density. He kept healthy bones despite taking a bone-leaching drug.

Just what sets us up for having healthy bones and keeping them healthy? Does a strong family history of osteoporosis lead us down a one-way street? Although osteoporosis is largely considered a women’s affliction, men make up one of every five cases of the disease, which is defined as an increased fracture risk due to a decrease in bone strength.

The Bone Equation
Let’s first understand what factors lay down optimal bone. During childhood, we all heard the adage, “drink milk for stronger bones”. It’s true. The bone mass attained early in life is perhaps the most important determinant of lifelong skeletal health. This crucial time extends until our mid- to late 20s, when our skeletons reach peak bone mass.

Genetic factors are the predominant influence during this time, but adequate nutrition, especially calcium and vitamin D, and physical activity play important roles. “You missed your best opportunity if, as a teen and young adult, you drank soda and played video games,” says Diane Feskanich, a Harvard University epidemiologist. Your “bone in the bank”, as they say, is probably low. Adequate body weight and sex hormones also contribute to higher bone mass, which is why anorexia nervosa and amenorrhea from under nutrition or strenuous athletic training can set the stage for osteoporosis.

There’s more to the skeletal equation than achieving optimal bone mass. In a process called bone turnover or remodeling, bone cells daily seek out damaged old bone tissue and churn out new bone, using minerals such as calcium and phosphorus. Around age 50, our bone loss begins to outpace bone growth at a rate of about 0.5% every year. Men are born with several advantages—they have stronger, thicker bones to begin with, and women go through an accelerated bone loss that jumps 2–5% a year during the five years around menopause. You would think the worst was over, but recent research indicates that men and women in their 80s undergo another acceleration in bone loss.

Preventive Diet?
Osteoporosis researchers agree that young people need adequate calcium for skeleton formation. But backed by clinical research, the daily recommendation for persons aged 51 and over was recently bumped up to 1200 mg, slightly less than the recommendation for children 18 and under. This requirement can be met by three servings of calcium-rich dairy products, but studies show that the average American consumes only 500–600 mg of calcium.

Many researchers disagreed with upping the over-51 recommendation, particularly for older men. “With so many people not eating dairy products, we’ll have a population taking supplements,” says Feskanich. “It doesn’t say that, but it’s implied by the recommended amount.” Nondairy eaters are encouraged to consume high-calcium sources such as fortified soy products, broccoli, spinach, dried beans, almonds, and bony fish.

Feskanich and others also cite population studies and prostate cancer research. “You don’t have osteoporosis in Asian countries where calcium intake is extremely low, but there are high fracture rates in the Scandinavian countries where there’s high calcium and dairy intake,” says Feskanich, who specializes in osteoporosis fracture research.

Harvard University physician Ed Giovannucci also recommends a lower amount for men. “Although controversial, there’s at least some evidence from our study and several others that high calcium intakes may increase risk of metastatic prostate cancer,” says Giovannucci. “While more work needs to be done in this area, it would be prudent to wait before increasing recommendations, particularly in men.”

Perhaps as important as calcium is vitamin D, called the sunshine vitamin since our skin produces it during exposure to sunlight. We require vitamin D to absorb calcium. If you’re homebound or live in the north during winter, your limited sun exposure may not produce adequate amounts of vitamin D. Few foods contain high vitamin D (milk, egg yolks, fatty fish), so unless you get plenty of sun or drink lots of milk, the amount of vitamin D in a standard multivitamin should be sufficient for people under 70. Older folks need slightly higher amounts.

History and Exercise
If you have a parent who exhibited the osteoporotic hump or suffered numerous fractures, a family history of osteoporosis does put you at higher risk, but no more than family history predicts heart disease. “It’s not known how much of this is genetics and how much is lifestyle being passed down,” says Feskanich. “Despite a family history, you can adopt a lifestyle that won’t doom you to osteoporosis.”

Physical activity is one of those lifestyle suggestions. High-impact exercise, such as jogging, weight training, or anything that involves jumping, stimulates bone mass the most as bone-building quickens in an attempt to reinforce the skeleton. But researchers suggest that any type of activity is beneficial.

“As muscles pull on the bones, they stimulate the bone. Walking three times a week is much better than doing nothing,” says Feskanich. It’s not too late if you weren’t active as a kid. Research continues to show that exercise and weight training build bone at all ages.

Besides the positive effect on bone, exercise helps us avoid falls as we age. Less fit and sedentary people are more likely to fall in the first place, says pharmacologist Mary Elliott of the University of Wisconsin, who studies osteoporosis in men. “You’re not as coordinated and, when you fall, you’re less likely to catch yourself. You also don’t have as much muscle tone to give you padding.”

Secondary Causes
Men develop secondary osteoporosis primarily as a result of medications or diseases. “The men I tend to worry about most are the little old skinny guys who smoke,” says Elliott. “Smoking affects their bone structure, and their smaller weight means less pressure on bones when they walk or exercise.”

The more common secondary causes for both men and women are hypogonadism (too little testosterone or estrogen), alcoholism, glucocorticosteroid use (primarily prednisone) and, for women, early menopause and thyroid medication. The use of anticonvulsants and certain diuretics (Furosemide, Lasix) also increase osteoporosis risk.

Of the medications, chronic prednisone use is a concern because it tears down the more active meshwork “trabecular” bone. Recent research shows as little as 2.5 mg of daily oral prednisone for 2 months or longer increases bone loss. “The key thing is for the patient to be maintained on the lowest dosage possible,” says Elliott. Those on thyroid replacement therapy should also be checked regularly to make sure their dosage isn’t too high. Regarding alcohol, as with the recommendations for heart disease, moderate consumption appears to maintain bone density while heavy use has a negative effect.

Latest Treatments
In the past, hormone replacement therapy (HRT) was the best hope for reducing bone fractures in women. But that picture has changed in the past five years with the addition of medications specifically for osteoporosis, along with a lack of research on the ability of HRT to reduce fractures. Bruce Ettinger of the University of California–San Francisco, who has studied estrogen since 1972, is looking forward to definitive answers from the Women’s Health Initiative about estrogen and fractures in older women, which will be available in about three years.

Current drug therapies all work on the bone loss part of the skeletal equation; they slow down breakdown, allowing bone replacement to exceed bone loss. Shook’s doctor put her on Fosamax (alendronate), a bisphosphonate drug. Other common medications include Evista (raloxifene), the first in a new class of drugs called selective estrogen receptor modulators that work like estrogen but apparently without the risk of breast and uterine cancer. Miacalcin (calcitonin) is a nasal spray used to reduce spinal fractures. And, of course, any drug therapy should include adequate calcium and vitamin D. Calcium citrate supplements are absorbed slightly better than calcium carbonate.

One problem with all these medications is that you need to take them for life. They hold osteoporosis at bay, but they don’t give you back the bones of a 20-year-old. How fast bone loss resumes after discontinuation depends on the drug. According to Ettinger, the rate of bone loss is higher after women stop taking HRT and Evista than with bisphosphonates such as Fosamax.

Hormone Builds Bone
With new drugs in development, the options undoubtedly will be different five years from now. Of these, parathyroid hormone excites many doctors because it actually builds bone. However, it currently needs to be injected—not a popular method among potential users. “Pharmaceutical companies will move heaven and earth to get it into another form, even a nasal spray,” says Elliott.

So in the meantime, do what your mother told you: Drink your milk, get out in the sun (but not too much), and move your body. Those tips just may help you keep moving your body into a healthy old age.

Further Reading

  • Bemben, D. A. Osteoporosis and exercise. Med. Sci. Sports Exerc. 1995, 27, i–vii.
  • Feskanich, D. Moderate alcohol consumption and bone density among postmenopausal women. J. Women’s Health 1999, 8, 65–73.
  • Fox, K. M.; Cummings, S. R.; Powell-Threets, K.; Stone, K. Family history and risk of osteoporotic fracture. Study of Osteoporotic Fractures Research Group. Osteoporos. Int. 1998, 8, 557–562.
  • Layne, J. E.; Nelson, M. E. The effects of progressive resistance training on bone density: A review. Med. Sci. Sports Exerc. 1999, 31, 25–30.
  • Osteoporosis prevention, diagnosis, and therapy. JAMA 2001, 285, 785–795.


Linda Richards is a freelance writer living in Flagstaff, AZ. Send your comments or questions regarding this article to tcaw@acs.org or the Editorial Office 1155 16th St N.W., Washington, DC 20036.

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