Much Caffeine May Weaken Bones
(HealthScoutNews) -- While
another cup of morning java may give grandma the jolt of energy
she needs, the benefits may not be worth the risks. A new study
shows too much caffeine can weaken bones in older women.
Post-menopausal women who consumed more than 300 milligrams
of caffeine daily (about three 6-ounce cups of American-brewed
coffee) were far more likely to have lower bone mineral density
-- a measurement of bone strength -- than women who consumed less,
says a study in this month's American Journal of Clinical Nutrition.
"It's important to realize we're not just talking about
coffee, but all forms of caffeine -- tea, soda, chocolate. When
the total amount goes over a certain limit, the risk of bone loss
increases," says study author Dr. J.C. Gallagher, director
of the Bone Metabolism Unit at Creighton University in Nebraska.
While the idea that caffeine could speed bone loss is not new,
Gallagher says a lack of scientific proof prompted the new study.
"We looked at 500 women over a period of three years, and
we could see the relationship between caffeine and bone loss quite
clearly," says Gallagher.
In addition, he says women who possessed a particular version
of a vitamin D receptor (VDR) appeared to have even greater bone
loss because of caffeine.
"The increase was significant -- at least several times
more bone loss was experienced by these women when caffeine was
consumed," says Gallagher. Vitamin D helps bones absorb calcium
and signals the kidneys to retain calcium.
Good bone density reduces the risk of osteoporosis, a painful
and potentially debilitating disorder that causes bones to thin,
become brittle and break easily.
For nutritionist Samantha Heller, however, the relationship between
caffeine and bone loss is not so cut and dried.
"Several studies have found little or no relationship between
bone density and caffeine consumption. There are other studies
that suggest differently," she says.
The only thing we really know for certain is that caffeine increases
urinary excretion of calcium, a mineral necessary for bone health,
she says. The new findings may indicate the effects of caffeine-related
calcium loss more than any direct effect of caffeine on bone health,
The study looked at the caffeine consumption of nearly 500 post-menopausal
women, aged 66 to 75, over three years. Each woman took a calcium
and a vitamin D supplement daily, while an additional 96 women
only took a placebo.
At the start of the study, doctors took bone density measurements
of the hip and spine and used complex genetic testing to determine
the presence of a particular type of vitamin D receptor.
The women were then asked to keep a diary of caffeine consumption,
including coffee, tea and other beverages.
After three years, the women were divided into two groups: those
who consumed more than 300 milligrams of caffeine daily and those
who consumed less. The two groups were then further divided according
to whether they had the specific vitamin D receptor cells.
"When the measurements were taken again, we found that the
women who consumed more than 300 milligrams of caffeine daily
had a significantly greater loss in bone mineral density than
those who consumed under 300 milligrams," says Gallagher.
Those with a particular type of vitamin D receptor cells had an
even greater loss when caffeine was consumed, he says.
The association between caffeine and bone loss prevailed even
after researchers adjusted results for other factors linked to
bone loss, including smoking, age, alcohol and calcium intake.
What To Do
In an editorial accompanying the study, Linda K. Massey of Washington
State University, in Spokane, writes that until doctors can readily
identify women who carry the genetic risk associated with vitamin
D receptors, it's too soon to advise all women to avoid caffeine
altogether. Instead, she suggests moderate caffeine intake with
adequate calcium consumption.
Gallagher endorses that suggestion.
"As is often the case, moderation is the key here. If caffeine
consumption is kept under 300 milligrams daily, a woman may have
some protection against bone loss," he says.
Moderate caffeine consumption in terms of coffee is about 16
ounces daily. The suggested amount for tea, which contains less
caffeine, is about 32 ounces daily.
And if you do consume a lot of caffeine, keep calcium intake
"Although peak bone mass is attained early on, a poor diet
and lack of exercise can diminish the calcium stores we do have
and increases our risk for osteoporosis," says Heller.
She says a woman's best defenses include eating lots of calcium-rich
foods, such as low-fat dairy products and leafy green vegetables,
and getting plenty of regular exercise.
For more information on bone health visit the
National Osteoporosis Foundation.
To learn if you're getting enough calcium in your diet, check
For more on caffeine and a guide to caffeine content in common
foods and beverages, visit
The McKinley Health Center.
Reference Source 101