Protecting your bones
P H Y S I C I A N S C O M M I T T E E F O R R E S P O N S I B L E M E D I C I N E
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The bone-thinning condition called osteoporosis can 3. Get vitamin D from the sun, or supplements if you need them.
lead to small and not-so-small fractures. Althoughmany people think of calcium in the diet as good pro-
Vitamin D controls your body’s use of calcium. About 15
tection for their bones, this is not at all the whole story. In
minutes of sunlight on your skin each day normally pro-
fact, in a 12-year Harvard study of 78,000 women, those who
duces all the vitamin D you need. If you get little or no sun
drank milk three times a day actually broke more
exposure, you can get vitamin D from any multiple vitamin.
women who rarely drank milk.1 Similarly, a 1994 study of
The Recommended Dietary Allowance is 200 IU (5 micro-
elderly men and women in Sydney, Australia, showed that
grams) per day. Vitamin D is often added to milk, but the
higher dairy product consumption was associated with in-
amount added is not always well controlled.
fracture risk. Those with the highest dairy productconsumption had approximately double the risk of hip frac-
How to Keep It There
ture compared to those with the lowest consumption.2
To protect your bones you do need calcium in your
diet, but you also need to keep calcium in your bones.
It’s not enough to get calcium into your bones. What is
really critical is keeping it there. Here’s how:
How to Get Calcium into Your Bones
1. Reduce calcium losses by avoiding excess salt.
1. Get calcium from greens, beans, or fortified foods.
Calcium in bones tends to dissolve into the bloodstream,then pass through the kidneys into the urine. Sodium (salt)
The most healthful calcium sources are green leafy vegetables
in the foods you eat can greatly increase calcium loss
and legumes, or “greens and beans” for short. Broccoli, Brus-
through the kidneys.3 If you reduce your sodium intake to
sels sprouts, collards, kale, mustard greens, Swiss chard, and
one to two grams per day, you will hold onto calcium bet-
other greens are loaded with highly absorbable calcium and a
ter. To do that, avoid salty snack foods and canned goods
host of other healthful nutrients. The exception is spinach,
with added sodium, and keep salt use low on the stove and
which contains a large amount of calcium but tends to hold
onto it very tenaciously, so that you will absorb less of it.
Beans are humble foods, and you might not know that
2. Get your protein from plants, not animal products.
they are loaded with calcium. There is more than 100 milligramsof calcium in a plate of baked beans. If you prefer chickpeas,
Animal protein—in fish, poultry, red meat, eggs, and dairy
tofu, or other bean or bean products, you will find plenty of
products—tends to leach calcium from the bones and en-
calcium there, as well. These foods also contain magnesium,
courages its passage into the urine. Plant protein—in
which your body uses along with calcium to build bones.
beans, grains, and vegetables—does not appear to have this
If you are looking for a very concentrated calcium
source, calcium-fortified orange or apple juices contain 300milligrams or more of calcium per cup in a highly absorb-
3. Don’t smoke.
able form. Many people prefer calcium supplements, whichare now widely available.
Smokers lose calcium, too. A study of identical twins
Dairy products do contain calcium, but it is accompa-
showed that, if one twin had been a long-term smoker and
nied by animal proteins, lactose sugar, animal growth fac-
the other had not, the smoker had more than a 40 percent
tors, occasional drugs and contaminants, and a substantial
amount of fat and cholesterol in all but the defatted versions.
American recommendations for calcium intake are high,
2. Exercise, so calcium has somewhere to go.
partly because the meat, salt, tobacco, and physical inactivityof American life leads to overly rapid and unnatural loss of
Exercise is important for many reasons, including keeping
calcium through the kidneys. By controlling these basic fac-
bones strong. Active people tend to keep calcium in their
tors, you can have an enormous influence on whether cal-
bones, while sedentary people lose calcium.
cium stays in your bones or drains out of your body.
Hormone Supplements Have Serious Risks
Calcium and Magnesium in Foods
Some doctors recommend estrogen supplements for
women after menopause as a way to slow osteoporosis,
although the effect is not very great over the long run, and
they are rarely able to stop or reverse bone loss.
Many women find these hormones distasteful because
the most commonly prescribed brand, Premarin, is made from
pregnant mares’ urine, as its name suggests. What has many
physicians worried is the fact that estrogens increase the risk
of breast cancer. The Harvard Nurses’ Health Study found that
women taking estrogens have 30 to 80 percent more breast
Moreover, Premarin may aggravate heart problems. In a
study of 2,763 postmenopausal women with coronary dis-
ease followed for an average of four years, there were as manyheart attacks and related deaths in women treated with the
combined regimen of estrogens and a progesterone deriva-
tive, as with placebo, but the coronary problems occurred
sooner in women taking hormones. Hormone-treated women
were also more likely to develop dangerous blood clots and
gallbladder disease.7 Controlling calcium losses is a much safer
If you already have osteoporosis, you will want to speak
with your doctor about exercises and perhaps even medi-
Osteoporosis in Men
Osteoporosis is less common in men than in women, and
its causes are somewhat different. In about half the cases,
Source: J.A.T. Pennington, Bowes and Church’s Food Values of Portions
a specific cause can be identified and addressed:8
Commonly Used. (Philadelphia: J.B. Lippincott, 1994.)
• Steroid medications
, such as prednisone, are a common
cause of bone loss and fractures. If you are receiving ste-roids, you will want to work with your doctor to mini-mize the dose and to explore other treatments.
can weaken your bones, apparently by reducing
1. Feskanich D, Willett WC, Stampfer MJ, Colditz GA. Milk, dietary calcium,
and bone fractures in women: a 12-year prospective study. Am J Publ
the body’s ability to make new bone to replace normal
losses. The effect is probably only significant if you have
2. Cumming RG, Klineberg RJ. Case-control study of risk factors for hip
more than two drinks per day of spirits, beer, or wine.
fractures in the elderly. Am J Epidemiol 1994;139:493-503.
• A lower than normal amount of testosterone
3. Nordin BEC, Need AG, Morris HA, Horowitz M. The nature and signifi-
age osteoporosis. About 40 percent of men over 70 years
cance of the relationship between urinary sodium and urinary calcium in
of age have decreased levels of testosterone.
4. Remer T, Manz F. Estimation of the renal net acid excretion by adults
consuming diets containing variable amounts of protein. Am J Clin Nutr
In many of the remaining cases, the causes are excessive
calcium losses and inadequate vitamin D. The first part of
5. Hopper JL, Seeman E. The bone density of female twins discordant for
the solution is to avoid animal protein, excess salt and caf-
tobacco use. N Engl J Med 1994;330:387-92.
feine, and tobacco, and to stay physically active in order to
6. Colditz GA, Stampfer MJ, Willett WC, et al. Type of postmenopausal hor-
reduce calcium losses. Second, take vitamin D supplements
mone use and risk of breast cancer: 12-year follow-up from the Nurses’Health Study. Cancer Causes and Control 1992;3:433-9.
as prescribed by your physician. The usual amount is 200
7. Hulley S, Grady D, Bush T, et al. Randomized trial of estrogen plus proges-
IU (5 micrograms) per day, but it may be doubled if you
tin for secondary prevention of coronary heart disease in postmenopausal
get no sun exposure at all. If you have trouble absorbing
calcium due to reduced stomach acid, your doctor can rec-
8. Peris P, Guanabens N, Monegal A, et al. Aetiology and presenting symp-
ommend hydrochloric acid supplements.
toms in male osteoporosis. Br J Rheumatol 1995;34:936-41.
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