Boning Up on Osteoporosis
Consider an insidious condition that drains
away bone--the hardest, most durable substance in the body.
It happens slowly, over years, so that often neither doctor
nor patient is aware of weakening bones until one snaps
unexpectedly. Unfortunately, this isn't science fiction.
It's why osteoporosis is called the silent thief.
And it steals more than bone. It's the primary
cause of hip fracture, which can lead to permanent disability,
loss of independence, and sometimes even death. Collapsing
spinal vertebrae can produce stooped posture and a "dowager's
hump." Lives collapse too. The chronic pain and anxiety
that accompany a frail frame make people curtail meaningful
activities because, in extreme cases, the simplest things
can cause broken bones: Stepping off a curb. A sneeze. Bending
to pick up something. A hug. "Don't touch Mom, she might
break" is the sad joke in many families.
Osteoporosis leads to 1.5 million fractures,
or breaks, per year, mostly in the hip, spine and wrist,
with the cost of treatment estimated at $17 billion and
rising, according to the National Institutes of Health (NIH).
It threatens 34 million Americans, mostly older women, but
older men get it too. One in 2 women and 1 in 4 men older
than 50 will suffer a vertebral fracture, according to the
NIH. These numbers are predicted to rise as the population
ages.
Osteoporosis, which means "porous bones,"
is a condition of excessive skeletal fragility resulting
in bones that break easily. A combination of genetic, dietary,
hormonal, age-related, and lifestyle factors all contribute
to this condition. The osteoporosis seen in postmenopausal
women is the most common and best-studied, but there are
other causes that may be treated differently.
Changing attitudes and improving technology
are brightening the outlook for people with osteoporosis.
Nowadays, many women live 30 years or more--perhaps a quarter
to a third of their lives--after menopause. Improving the
quality of those years has become an important health care
goal. Although some bone loss is expected as people age,
osteoporosis is no longer viewed as an inevitable consequence
of aging. Diagnosis and treatment need no longer wait until
bones break.
There is no cure or proven preventive treatment
for osteoporosis, but the onset can be delayed and the severity
diminished. Most important, early intervention can prevent
devastating fractures. The Food and Drug Administration
has revised labeling on foods and supplements to provide
valuable information about the level of nutrients that help
build and maintain strong bones. The FDA has also approved
a wide variety of products to help diagnose and treat osteoporosis,
including several in the last few years.
Osteoporosis has been described as a geriatric
disease with an adolescent onset, highlighting the importance
of beginning to take steps--in exercise and diet--early
in life to reduce its disabling impact in later years.
Bone Life
Bone consists of a matrix of fibers of the
tough protein collagen, hardened with calcium, phosphorus
and other minerals. Two types of architecture give bones
strength. Surrounding every bone is a tough, dense rind
of cortical bone. Inside is spongy-looking trabecular bone.
Its interconnecting structure provides much of the strength
of healthy bone, but it is especially vulnerable to osteoporosis.
"We tend to think of the skeleton as an inert
erector set that holds us up and doesn't do much else. That's
not true," says Karl L. Insogna, M.D., director of the Bone
Center at Yale School of Medicine in New Haven, Conn. Every
bit as dynamic as other tissues, bone responds to the pull
of muscles and gravity, repairs itself, and constantly renews
itself.
Besides protecting internal organs and allowing
us to move about, bone is also involved in the body's handling
of minerals. Of the 2 to 4 pounds of calcium in the body,
nearly 99 percent is in the teeth and skeleton. The remainder
plays a critical role in blood clotting, nerve transmission,
muscle contraction (including heartbeat), and other functions.
The body keeps the blood level of calcium within a narrow
range. When needed, bones release calcium.
A complex interplay of many hormones balances
the activity of the two types of cells--osteoclasts and
osteoblasts--responsible for the continuous turnover process
called remodeling. Osteoclasts break down bone, and osteoblasts
build it. In youth, bone building prevails. Bone mass peaks
by about age 30, then bone breakdown outpaces formation,
and density declines, since the volume of bone remains about
the same.
The skeleton is like a retirement account
for minerals, but in our skeletal "account" we can deposit
bone faster than we withdraw it only during our first three
decades. After that, withdrawals are greater than deposits,
and all we can do is try to minimize the net loss. Osteoporotic
fractures are the sign of the bankruptcy that occurs when
too little bone is formed during youth, or too much is lost
later, or both.
"You've got to get as much bone as you can
and not lose it," Insogna says. "The most important risk
factor for osteoporosis is a low bone mass."
"The upper limit of bone mass that you can
acquire is genetically determined," says Mona S. Calvo,
Ph.D., a calcium expert in the FDA's Center for Food Safety
and Applied Nutrition. "But even though you may be programmed
for high bone mass, other factors can influence how much
bone you end up with," she says. For instance, men tend
to build greater bone mass, which is partly why more women
face osteoporosis.
But there's another reason. With the decline
of the female hormone estrogen at menopause, usually around
age 50, bone breakdown markedly increases. For several years,
women lose bone two to four times faster than they did before
menopause. The rate usually slows down again, but some women
may continue to lose bone rapidly. By age 65, some women
have lost half their skeletal mass.
Diagnosis
Because the changes at menopause increase
a woman's risk, many physicians feel it's a good time to
measure a woman's bone mineral density, especially if she
has other risk factors for osteoporosis.
"The best way to gauge a woman's risk for
osteoporotic fracture is to measure her bone mass," says
Insogna.
Routine X-rays can't detect osteoporosis until
it's quite advanced, but other radiological methods can.
The FDA has approved several kinds of devices that use various
methods to estimate bone density. Most require far less
radiation than a chest X-ray. Doctors consider a patient's
medical history and risk factors in deciding who should
have a bone density test. The method used is often determined
by the equipment available locally. Readings are compared
to an internationally accepted standard based on young Caucasian
women. Different parts of the skeleton may be measured,
and low density at any site is worrisome.
Bone density tests are useful for confirming
a diagnosis of osteoporosis if a person has already had
a suspicious fracture, or for detecting low bone density
so that preventive steps can be taken.
"There's a profound relationship between bone
mass and risk of fracture," says Robert Recker, M.D., director
of the Osteoporosis Research Center at Creighton University
in Omaha, Neb.
Readings repeated at intervals of a year or
more can determine the rate of bone loss and help monitor
treatment effectiveness. However, estimates are not necessarily
comparable between machine types because they use different
measurement methods, cautions Joseph Arnaudo, in the FDA's
Center for Devices and Radiological Health. "You always
want to go back to the same machine, if you can," he says.
A newer technique for evaluating bone strength
is ultrasound, and the FDA has approved several instruments
for this purpose. "These machines use the same principles
that are employed when using ultrasound to look at fetuses
during pregnancy," says Leo Lutwak, M.D., Ph.D., of the
FDA's Division of Reproductive, Abdominal, and Radiological
Devices. "Although this measurement examines different properties
of bone than do X-ray-based bone densitometers, the results
are also useful for prediction of fracture." The devices
for ultrasound measurement are cheaper and easier to use.
This makes them available in more locations and allows evaluation
for osteoporosis in many more subjects. "Because they don't
use X-rays, they are safer and may be used for repeated
examinations, even in pregnant women and children, so they
provide a means for better public health practice," Lutwak
says.
Another new test provides an indicator of
bone breakdown. In 1995, the FDA approved a simple, noninvasive
biochemical test that detects in a urine sample a specific
component of bone breakdown, called NTx. Clinical labs can
get results in about 2 hours. The NTx test, marketed as
Osteomark, can help physicians monitor treatment and identify
fast losers of bone for more aggressive treatment, but the
test doesn't measure bone metabolism specifically, so it
may not be used to diagnose osteoporosis.
Expanding Treatment Options
Physicians and patients now have more treatment
options. Under FDA guidelines, drugs to treat osteoporosis
must be shown to preserve or increase bone mass and maintain
bone quality in order to reduce the risk of fractures.
An important treatment option became available
to women in November 2002. Forteo (teriparatide) is the
first treatment that stimulates new bone growth to increase
bone mass. Forteo is a portion of human parathyroid hormone,
which works in the body to regulate the metabolism of calcium
and phosphate in bones. The treatment is given in daily
injections and is approved for postmenopausal women who
are at high risk for bone fractures.
The approval of this treatment comes with
a strong caution from the FDA: In the pre-approval studies
of Forteo using rats, there was an increase in the incidence
of osteosarcoma, a rare but serious cancer of the bone.
Because it's possible that women treated with Forteo could
have increased risk for developing this cancer, doctors
are advised to discuss this risk with their patients and
be sure that it's the best treatment. Women who are prescribed
Forteo receive an FDA-approved medication guide that explains
the benefits and risks and gives other advice about how
to use the treatment properly.
All other drugs approved for osteoporosis
treatment act by slowing the turnover of bone, rather than
stimulating new bone formation. Increases in bone mass are
most pronounced in the first year or two after treatment
with the drugs begins, then taper off. Any gain is helpful,
even if it doesn't continue, because increases in bone mass
help reduce fracture risk.
In the mid-1990s, the FDA approved the first
nonhormonal treatment for osteoporosis. Alendronate, marketed
as Fosamax, falls within a class of drugs called bisphosphonates.
In clinical trials, Fosamax increased the bone mass as much
as 8 percent and reduced fractures as much as 30 percent
to 40 percent, depending on skeletal site.
To avoid damage to the esophagus, Fosamax
should be taken according to the instructions. These instructions
include taking the drug in the morning upon awaking and
at least half an hour before eating. The drug should be
taken with a glass of water, and the person should remain
upright for half an hour after taking it. Fosamax should
not be taken by people who cannot stand or sit upright or
who have disorders that prevent esophageal emptying into
the stomach.
Other drugs recently approved for the prevention
and treatment of osteoporosis are Actonel (risedronate),
a bisphosphonate similar to Fosamax, and Evista (raloxifene),
a drug in a class known as selective estrogen receptor modulators,
or SERMs. Both drugs have been shown to reduce the risk
for fracture of the spine.
Calcitonin is a hormone that plays a role in calcium and
bone metabolism. When used regularly, it can slow the loss
of bone. Available for many years as an injection, calcitonin
treatment became much easier when FDA approved a nasal spray.
Fluoride, known for fighting dental cavities,
stimulates bone building, but studies in osteoporosis patients
have found that the structure of the new bone was abnormal
and weaker than normal bone.
While estrogen may be a good option for some
women, new guidelines developed in 2003 by the FDA advise
doctors to consider alternative treatments. These changes
were prompted by studies indicating that women who take
estrogen or estrogen with progestin products after menopause
are at higher risk for other conditions, including cardiovascular
disease and breast cancer. Because of this, estrogen-containing
products should only be considered for women at significant
risk of osteoporosis.
Drugs Not Enough
Calcium and vitamin D supplements are an integral
part of all treatments for osteoporosis. At the same time,
people who take supplements should keep in mind that it
is possible to consume excess amounts of these and other
nutrients. Attention to diet and exercise are important
not only for treatment, but also for prevention.
"If you go to the doctor and get a prescription,
and that's all you do, you're probably not going to be helped
very much," Recker says.
Calcium intake is critical, and those who
need it most--younger women and girls--may not get enough.
(See "Calcium (Ac)Counts.") But calcium
alone can't build bones. Vitamin D is needed to help the
body absorb calcium. Most people appear to get enough vitamin
D because the skin produces it in sunlight. And many foods,
such as milk products and breakfast cereals, are fortified
with vitamin D. But older adults and people with little
exposure to sunlight may need a vitamin D supplement.
A lifelong habit of weight-bearing exercise,
such as walking or biking, also helps build and maintain
strong bone. The greatest benefit for older people is that
physical fitness reduces the risk of fracture, because better
balance, muscle strength, and agility make falls less likely.
Exercise also provides many other life-enhancing psychological
and cardiovascular benefits. Increased activity can aid
nutrition, too, because it boosts appetite, which is often
reduced in older people. The biggest reason older people
don't get enough calcium, Recker says, is that they simply
don't eat much.
"The truth is, you don't have to do very much
to get most of the benefits of exercise," Recker says. He
suggests 30 minutes of brisk walking five days a week. Add
a little weightlifting, and that's even better. It's always
smart to ask your doctor before starting a new exercise
program, especially if you already have osteoporosis or
other health problems.
Brighter Horizons
The search for bone-building drugs continues.
Some naturally occurring bone-specific growth factors have
been identified and their use as drugs is being investigated.
"The way I visualize the ideal future is that we'll be able
to give Drug X that builds up bone to where it's stronger
and the risk of fracture is no longer present, then Drug
Y maintains it by preventing breakdown," says Paula Stern,
Ph.D., a pharmacologist at Northwestern University Medical
School in Chicago.
The study of risk factors also continues.
"We consider that to be the research that has the greatest
public health significance," says Sherry Sherman, Ph.D.,
of the National Institute on Aging.
Reducing Your Risk
Many factors can affect your chances of developing
osteoporosis. The good news is that you control some of
them. Even though you can't change your genes, you can still
lower your risk with attention to certain lifestyle changes
that will help build and maintain bone mass. The younger
you start, and the longer you keep it up, the better.
Here's what you can do for yourself:
- Be sure you get enough calcium and vitamin D.
- Engage in regular physical activity, such as walking.
- Don't smoke.
- If you drink alcohol, do so in moderation.
A sedentary lifestyle, smoking, excessive
drinking, and low calcium intake all increase risk.
Other factors are beyond your control. Being
aware of them can provide extra motivation and can help
you and your doctor to make health care decisions. These
risk factors are:
- being female
Women are at five times greater risk than men.
- thin, small-boned frame
- broken bones or stooped posture in older family members,
especially women, which suggest a family history of
osteoporosis
- early estrogen deficiency in women who experience
menopause before age 45, either naturally or resulting
from surgical removal of the ovaries
- estrogen deficiency due to abnormal absence of menstruation
(as may accompany eating disorders)
- ethnic heritage
White and Asian women are at highest risk; African-American
and Hispanic women are at lower, but significant, risk.
- advanced age
- prolonged use of some medications
These medications include some antiseizure medications,
glucocorticoids (certain anti-inflammatory medications,
such as prednisone, used to treat asthma, arthritis
and some cancers), certain cancer treatments, some treatments
for endometriosis, excessive use of aluminum-containing
antacids, and excessive thyroid hormone. It is important
to discuss the use of these drugs with your physician,
and not to stop or alter your medication dose on your
own.
- growth hormone deficiency in children and youth.
Risk factors may not tell the whole story.
You may have none of these factors and still have osteoporosis.
Or you may have many of them and not develop the condition.
It's best to discuss your specific situation with your doctor.
Calcium (Ac)Counts
Your skeletal calcium bank has to last through
old age. Frequent deposits to this retirement account should
begin in youth and be maintained throughout life to help
minimize withdrawals. Recommendations for daily calcium
intakes were established a few years ago by the Institute
of Medicine.
Nutritionists recommend meeting your calcium
needs with foods naturally rich in calcium. Adequate calcium
intake in childhood and young adulthood is critical to achieving
peak adult bone mass, yet many adolescent girls replace
milk with nutrient-poor beverages like soda pop. "Bone health
requires a lot of nutrients and you're likely to get most
of them in dairy products," says Connie Weaver, Ph.D., who
heads the department of foods and nutrition at Purdue University.
"They're a huge package rather than just a single nutrient."
With so many low-fat and nonfat dairy products available,
it's easy to make dairy foods part of a healthy diet. People
who have trouble digesting milk can look for products treated
to reduce lactose. A serving of milk or yogurt contains
about 350 milligrams of calcium. Fortified products have
even more.
"People who don't consume dairy foods can
meet their calcium needs with foods that are fortified with
calcium, such as orange juice, or with calcium supplements,"
says Mona S. Calvo, Ph.D., a calcium expert in the FDA's
Center for Food Safety and Applied Nutrition. Other good
sources of calcium are dark-green leafy vegetables like
kale and turnip greens, tofu (if made with calcium), canned
fish (eaten with bones), and fortified cereal products.
The food label can help you identify foods
that are a good source of calcium and other nutrients important
for bone health, such as vitamin D. You can use the Nutrition
Facts found on the label to see if a food is a good source
of these nutrients--that is, if it has at least 10 percent
of the Daily Value (DV) per serving. Also, if a food has
at least 10 percent of the DV, the label may bear a claim
that it is a good source of a nutrient. If it has 20 percent
or more, the label can say that it is "high" in or an "excellent
source." Some foods that are excellent sources of calcium
may also bear a health claim about the role of diet and
other factors in reducing the risk of osteoporosis.
But keep in mind that foods with smaller amounts
(such as between 5 percent and 10 percent of the DV) can
still make significant contributions to your daily calcium
intake. This may be especially true if you often eat more
than one serving of the food in a day, or if your actual
serving size is typically larger than the one on the label.
Finally, remember that label values are based
on a single Daily Value established by the FDA for food
labeling purposes--1000 milligrams in the case of calcium.
They do not take into account that some age groups have
lower or higher recommendations for intake.
What about too much calcium? A few years ago,
the Institute of Medicine established a level of 2,500 milligrams
as an upper intake level for calcium for most people. While
intakes considerably above this level may be safe for many,
others may be particularly susceptible to calcium's potentially
harmful effects at these levels. Those with higher sensitivities,
such as people at risk of kidney stones, should discuss
calcium with their doctors.
Calcium is critical, but even a high intake
won't fully protect you against bone loss caused by estrogen
deficiency, physical inactivity, alcohol abuse, smoking,
or medical disorders and treatments.
How Much Calcium Do You Need?
| Age |
Recommended Intake |
| 1-3 |
500 mg |
| 4-8 |
800 mg |
| 9-18 |
1300 mg |
| 19-50 |
1,000 mg |
| 51 and older |
1,200 mg |
