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Bone
density strategy dealt setback
By Shari Roan
Los Angeles
Times, September 22,
2003
Combining
two useful drugs doesn't make a more potent mix, one study shows, while
another casts an eye on effects of cola.
New medications can clearly help people with
osteoporosis. And because they work in different ways, scientists had
hoped to combine them using a double-barreled approach to fighting the
debilitating bone condition.
But hopes have been dashed for one especially promising combination.
A study reported last week at the annual meeting of the American Society
for Bone and Mineral Research found that using two popular drugs together,
alendronate and parathyroid hormone, are no better than either drug alone.
"The thought was that both would work better," says Dr. Bess
Dawson-Hughes, a professor of medicine at Tufts University and president
of the National Osteoporosis Foundation. "It's disappointing that
they don't. It's going to change the way doctors prescribe these
drugs."
Osteoporosis affects 10 million Americans and an additional 34 million
have low bone density and are at risk for the disease. Osteoporosis can
lead to hip fractures, physical decline and is a major cause of
nursing-home admissions among the elderly. The disorder is more prevalent
in women.
The study on the combination of parathyroid hormone therapy and
alendronate has been highly anticipated. Parathyroid hormone treatment was
approved late last year under the brand name Forteo as the first drug to
rebuild bone. Doctors had hoped it could be combined with existing
medications that slow bone loss, such as alendronate (brand name Fosamax)
or other biphosphonate drugs, such as risedronate (Actonel).
But in a study of 238 postmenopausal women, scientists from UC San
Francisco found that the combination worked no better than either drug
alone in strengthening bone in the spine and hip. Moreover, combining the
drugs may actually diminish the bone-building effects of parathyroid
hormone.
"What we usually see with parathyroid hormone is large increases in
bone formation," says Dr. Dennis Black, an epidemiology professor at
UC San Francisco and lead author of the study. "We didn't see that in
the combination therapy."
The study will be published this week in the New England Journal of
Medicine.
Doctors had believed that the drugs would work well together since each
acts differently on bone, says Dawson-Hughes. "There are lots of
patients who have been on alendronate and who still have
osteoporosis," she says. "The thinking was that maybe they'll
have a synergistic effect."
The new data should discourage doctors from prescribing parathyroid
hormone and biphosphonate drugs together but may also create some
confusion on which drug to use first, experts say. For example, doctors
don't know whether alendronate will interfere with parathyroid hormone if
one drug is given for a period of time before being stopped and the other
drug started.
"There's not real good data on what to do," Black says.
"Parathyroid hormone is very promising because it works so
differently than traditional therapies. But we don't know yet how to best
use it."
For now, doctors and patients should make individualized decisions on
which types of therapies to pursue; there are many treatments other than
parathyroid hormone and alendronate, Dawson-Hughes says.
Osteoporosis patients may also want to confer with their doctors about
their diets — especially soft-drink lovers. Health experts have long
suspected a link between soft drinks and reduced bone mineral density. But
research released Friday suggests that phosphoric acid in cola drinks may
be the problem.
Tufts University researcher Katherine Tucker examined the bone mineral
density readings of more 2,500 adult men and women and surveyed their
soft-drink consumption patterns, distinguishing among carbonated cola
drinks, carbonated non-cola drinks, and carbonated caffeine-free and diet
soft drinks. She found that women — but not men — who drank more than
three, 12-ounce servings of cola per day had 2.3% to 5.1% lower bone
mineral density in the hip compared with women who consumed less than one
serving of cola per day.
Similar results were seen with the diet and caffeine-free cola beverages
but not with non-cola carbonated beverages.
"This remains a very controversial area," says Tucker. "But
it seems that the phosphoric acid in cola drinks has a negative effect on
bone. When you have phosphoric acid in a cola beverage, the excess
phosphoric acid binds to calcium in the gut," which keeps the calcium
from being absorbed.
It's also possible that phosphoric acid can adversely affect parathyroid
hormone levels in the body, which regulate bone density, Tucker says.
Other studies are needed to test the theory, she adds, explaining that
some researchers doubt that the level of phosphoric acid in cola drinks is
high enough to contribute to low bone mineral density.
Experts have suggested that many people replace milk with soft drinks as
they grow older, which leads to lower bone mineral density because of the
loss of calcium from milk.
But in the new study, "we did not find that people drinking cola
beverages drank less milk than other people. Adults don't drink much milk
anyway," Tucker says.
Still, the interaction between diet and bone mineral density is complex,
she notes, as evidenced by the fact that no link between cola and lower
bone mineral density was found in men.
"Men have different beverage consumption patterns," says Tucker.
"They drink more alcohol, and alcohol can be protective of bone in
some ways." In research awaiting publication, Tufts researchers found
that beer appears to protect bone, possibly due to its silicone content.
In other research presented at the meeting, data from the Framingham
Study, an observational study of thousands of Framingham, Mass.,
residents, showed that a high level of the chemical homocysteine in the
blood is associated with future risk of osteoporosis and hip fracture.
Women with high homocysteine levels had double the hip fracture rate and
men with high levels had four times the increase compared with people with
low homocysteine levels. The levels can be influenced by diet,
particularly vitamin B-12 and folate, and by some medications.
Also, Holocaust survivors who were 17 or younger at the onset of World War
II are now reporting hip fracture rates that are more than 10 times higher
than individuals of the same ethnic group and age who did not live under
Nazi occupation. Researchers from Hadassah University in Jerusalem suggest
that poor diet and harsh conditions had an adverse effect on the amount of
bone accumulated during the growth period of childhood and adolescence.
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© 2002 Global Action on Aging
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