The Owner's Manual
For Your Skeleton!
in the Body
is crucial to maintain life; without it we would die. Just
about every cell in the body, including those in the heart,
nerves and muscles, relies on calcium to function properly.
Bones require calcium to maintain their strength. In the
body, calcium is found in three places:
in the skeleton;
in the cells;
in the blood.
levels of calcium in the blood determines the availability
of calcium to the various organs and the skeletal structure.
control the amount of calcium in the blood. Everyone constantly
loses calcium through urine, sweat, and feces, and it is
renewed with calcium from the bones. In the process, the
body constantly breaks down and rebuilds bones. Ultimately,
the body's calcium is replaced by calcium from food or mineral
The body carefully regulates its calcium absorption. The
body does this in three ways:
It absorbs calcium directly from the food that you eat.
This is the preferable way for the body to get calcium.
It takes calcium from your bones if there is not enough
available when it is needed. This makes the bones
thinner and fragile, and is the major cause of osteoporosis.
It slows down the amount of calcium leaving via the urine,
returning some to the blood stream where it remains available
to organs and cells.
average person absorbs 30 to 70 percent of the calcium she
or he eats. While milk is a source of calcium, it
certainly is not the ideal way to get your daily dose. Dairy
products, with the exception of skim products, are loaded
with saturated fat. Fat is directly related to heart disease
and cancer. Dairy products are also high in protein. There
are other reasons to worry about milk, too. Cows are routinely
fed antibiotics. These are then passed directly on to the
milk drinkers; antibiotics are detectable in one out of
three cartons of milk. Many people are also allergic to
milk, and over three-fourths of the world's population is
lactose-intolerant, which means their bodies lack the enzymes
necessary to digest milk.
The Need for Calcium
Throughout life, people's calcium needs change. Until about
age 35, people consume more calcium that their bodies lose.
But around age 45, the body begins to slip into "negative
calcium balance", slowly the body loses more calcium than
it takes in. As shown above, how rapidly calcium is lost
depends, in part, on how much protein is in the diet, and
the kind of protein it is. The loss of too much calcium
can lead to "soft bones," or osteoporosis.
the 1920's researchers have known that diets that are high
in protein, especially animal protein, cause calcium to
be lost through the urine. In nations with high rates of
osteoporosis, protein intake is generally high, usually
more than twice the U.S.
recommended daily allowance. Vegetarians have lower rates
of osteoporosis than meat eaters. This may be due to the
lower protein intake of vegetarians. Different types of
protein also affect this loss.
and sodium also increase the rate at which calcium is lost
through urine. Alcohol inhibits calcium absorption and may
also be toxic to bone. Vitamin D, copper, zinc, manganese,
fluorine, and boron are all essential for good bone formation,
and weight-bearing exercise also increases bone mass and
helps to prevent osteoporosis. Boron appears to help stop
the loss of calcium. The best way to get boron is through
fruits, vegetables, and beans.
Calcium is essential to bone health for a number of reasons.
In childhood, it is necessary to grow a healthy skeleton
to support a growing body.
age 20, bones typically stop growing in length. It is the
current scientific thinking that peak bone mass is reached
around this time. The density of your bones at this point
will depend, in part, upon the extent of your calcium intake
as a child. The greater this peak bone mass, the less likely
your bones are to become porous and fragile later on.
is living tissue, constantly renewing itself. Although bone
is strong and relatively flexible, everyday wear and tear
causes tiny structural defects, much like those that occur
in the specialized cells that perform the work of a "maintenance
crew." The first group excavates the defects to remove any
crumbling or weakened bone, then leaves the "site."
they have left, the second group moves in to fill the crevices.
The material that they deposit calcifies to form new bone.
This two-part process is called bone remodeling. Remodeling
is an ongoing, natural process and the cycle is completed
every three to four months in a healthy young adult.
you age, several things happen that make good calcium nutrition
just as important. First of all, the remodeling process
changes. The two groups of cells that form the maintenance
crew become less efficient in working together — the ones
that fill in the crevices are not able to rebuild the bone
as quickly because they are having trouble keeping up with
people who have relatively healthy bones, adequate calcium
intake can help the remodeling process stay balanced. This
means that replacement of new bone will remain more efficient,
thus preventing a rapid decline in density.
is less efficiently absorbed as you age. You need to be
even more vigilant about your calcium intake to protect
your bones. Despite the slowdown of calcium absorption and
less efficient remodeling, studies of older adults show
that adequate calcium intake can slow bone loss and reduce
the risk of fracturing.
There are two types of vegetarians: vegans, those who
do not eat any animal products whatsoever, and lacto-ovo
vegetarians, those who do not eat animal flesh (meat, poultry
or fish) but do eat animal products such as dairy foods.
on the relationship between vegetarianism and osteoporosis
have been done on lacto-ovo vegetarians; some studies with
lacto-ovo vegetarians with high calcium intake have shown
that this type of vegetarian has better bone density than
meat eaters on a low calcium diet. However, these vegetarians
are generally health conscious so it is difficult to determine
whether it is the diet-related aspect alone that is responsible
for these findings.
D for Calcium Absorption
Vitamin D is
crucial to calcium absorption. In fact, it increases calcium
absorption by as much as 30% to 80%. Adults should receive
400 IUs of vitamin D per day (older adults should receive
between 400 and 800).
easiest and most natural way to get Vitamin D is from exposure
to sunlight, which causes the body to manufacture its own.
Just 15 minutes a day of summer sun exposure, even if only
on the arms, face and hands, will greatly enhance Vitamin
Canada, where there is little sun intensity in the winter
months, Vitamin D production in the skin ceases from early
October until the end of March. If you are house-bound and
don't get out into the sunlight much, you are not able to
produce Vitamin D.
make up for a lack of sunlight, you must try to find other
sources. Although there are few food sources of Vitamin
D, milk does contain significant amounts. (Fortified with
Vitamin D, it contains 100 IUs per 250 ml glass). Foods
such as margarine, eggs, chicken livers, salmon, sardines,
herring, mackerel, swordfish, and fish oils (halibut and
cod liver oils) all contain small amounts.
it may be difficult to get enough Vitamin D from food alone,
you may wish to consider supplementation. Most multivitamins
provide 400 IUs of Vitamin D.
is not necessary to have vitamin D added to your calcium
supplement as long as you have the recommended daily intake
sometime during the day.
and Bone Health
Minerals like manganese, copper, and magnesium are important
for bone health as they play a part in bone remodeling.
Each has different activities, but deficiency in any of
them can lead to stunted growth and bone deformity. However,
you do not need a lot of these minerals every day and they
are widely available in many foods. Deficiency in those
with a varied diet would be quite unlikely.
also is available in the food that you eat and a serious
deficiency would be unlikely. There is no evidence to support
a role for zinc supplementation in the maintenance of good
calcium absorption in otherwise healthy adults. In fact,
high doses of zinc have been shown to inhibit calcium absorption
when calcium intake is low.
has been some research to show that the mineral boron may
play a role in bone metabolism but there is currently not
enough information to define just what that role is. Eating
a varied, healthy diet that provides adequate calcium intake
will usually ensure that your body gets the minerals that
maintain strong, healthy bones, you need to make a "lifetime
commitment" to getting enough calcium, warn experts from
the US Department of Agriculture (USDA). They report that
bone loss associated with aging climbs to pre-therapy levels
soon after calcium supplements are abandoned.
and osteoporosis experts have long advocated that individuals
meet recommended dietary allowances (RDAs) for calcium —
preferably from food — in order to build and maintain healthy
bone density. Calcium is especially important for adolescents,
who are building bone density to peak levels, and for post-menopausal
women, who lose bone density at about 1% per year. Loss
of bone density can cause osteoporosis and increase the
risk of fractures in the elderly.
a special study, doctors examined calcium intake and bone
density in nearly 300 men and women over the age of 65 for
a period of 2 years. All of the subjects had taken calcium
supplements for 3 years previous to the study.
large number of subjects told the researchers that they
had stopped calcium supplementation. The doctors reported
that "by 1 year after they stopped treatment," women who
had stopped the therapy "had no residual benefit in terms
of bone density."
other words, they resumed losing bone density at pre-treatment
rates. Men who abandoned supplements took a little longer
to see treatment effects vanish, but after 2 years of not
taking extra calcium, they, too, saw levels of bone loss
rise to pre-treatment levels. The bottom line, is
that there appears to be "no sustained benefit from calcium"
once treatment stops.
results were found in adolescents. Dr. Steven Abrams, a
pediatric researcher at the USDA/ARS Children's Nutrition
Research Center, in Houston, Texas, reviewed findings from
four 1-to-2-year trials in girls and boys aged 6 to 14 years.
benefit from calcium supplementation wasn't really held
once you stopped it," Abrams said, with bone development
(that is, increases in bone density) in adolescents who
stopped supplementation slowing to levels similar to those
seen in untreated children.
US government RDAs for calcium are 800 mg for children aged
4 to 8, 1300 mg for children aged 9 to 18, 1000 mg a day
for adults aged 19 - 49, and 1200 mg per day for adults
over age 50. Calcium is found in dairy products and in produce
such as collards, turnip greens, rhubarb, broccoli and kale.
Reduces Bone Loss, Fracture
Rate for Older People
The National Institute on Aging
September 3, 1997
of calcium and vitamin D can significantly reduce bone loss
and the risk of fractures in older people, according
to a new report from scientists at Tufts University. The
research, the first to show that these supplements can help
older men fight osteoporosis, also demonstrates that the
benefits of these low cost and easily available supplements
can be maintained over several years.
findings by Bess Dawson-Hughes, M.D., and colleagues of
the Jean Meyer U.S. Department of Agriculture Human Nutrition
Research Center on Aging at Tufts University appear in the
September 4, 1997, The New England Journal of Medicine.
The research was funded by the National Institute on Aging
(NIA) as part of its STOP/IT (Sites Testing Osteoporosis
Prevention/Intervention Treatments) initiative.
people can benefit from this therapy at essentially no risk
and at low cost," said Dawson-Hughes. "Our
research underscores the importance of calcium and vitamin
D supplementation in helping healthy and active older people
stay that way."
scientists noted the importance of the finding for older
men. "Until recently, osteoporosis has been considered
to be a women's problem," said Sherry Sherman, Ph.D.,
Director, Clinical Endocrinology and Osteoporosis Research,
NIA, and project officer for the study. "We know that
older men do experience considerable bone loss over time.
With people living longer than ever, increasing the intake
of calcium and vitamin D can be an important lifelong strategy
for both sexes."
researchers chose a combination of calcium and vitamin D
to take advantage of the vitamin's influence in helping
the body absorb and utilize calcium. As people age, the
absorption of calcium and, it is believed, vitamin D, declines,
as does production of vitamin D by the skin. This reduced
ability to absorb calcium contributes to bone loss as people
age, and low bone density is an underlying cause of increased
hip fracture among the elderly.
amounts of calcium and vitamin D used in the study are in
keeping with recent recommendations of a National Academy
of Sciences (NAS) panel, which recommended changes in current
dietary requirements for calcium and related nutrients.
The NAS group suggested that people over 50 increase their
daily intake of calcium to about 1,200 milligrams and found
that about 400-600 International Units of vitamin D (cholecalciferol)
would be adequate.
followed 389 men and women age 65 and older for 3 years.
The study participants kept to their usual diets, in which
they were generally getting the old recommended dietary
allowances of calcium and vitamin D. At bedtime, about half
of the study participants took placebo pills of no nutritional
value. The other half took two separate pills, one containing
500 milligrams of elemental calcium (calcium citrate malate)
and the other 700 International Units of vitamin D. All
participants visited Tufts every 6 months for measurements
of bone mineral density and other tests. Researchers also
noted the number of fractures that occurred during the study
the 3 years, the calcium/vitamin D group lost significantly
less total body bone, and, in some areas, gained
bone mineral density. In men, where the findings
were more pronounced, those taking placebos lost about one
percent of their bone density at the hip over 3 years. Men
taking the calcium/vitamin D combination increased their
bone density by about 1 percent. The benefit at
the hip for men, therefore, totaled a 2 percent improvement
in bone density for the supplemented group. For women, the
positive effects were most notable in the total body bone
density, with lesser effects at the hip and spine.
addition, the supplements may be effective in maintaining
the skeleton over the long term, Dawson-Hughes said. The
researchers found that the supplements were beneficial to
bone density at the hip, spine, and total body in the first
year, and further improved bone density of the total body
during the second and third years of the study. The initial
effects of supplementation at the hip and spine during the
first year held steady, but did not change appreciably,
over the next two years.
small losses of bone mass each year are important, scientists
say. The losses are cumulative and add up to significant
decreases in bone mineral density over time. "If we
could retard bone loss in older people, we could make a
lot of headway in preventing the devastation of osteoporosis
and the fractures that commonly come with it," said
group taking supplements did considerably better in avoiding
fractures. Some 5.9 percent of the participants
taking the calcium and vitamin D suffered fractures, compared
with 12.9 percent who did not take the supplements. Most
of the fractures occurred in women.
28 million middle-aged and older people are at risk
of osteoporosis, and hip fractures related to low
bone mass are a leading cause of nursing home entry for
NIA leads the Federal effort conducting and funding basic,
clinical, social, and behavioral research aimed at maintaining
independence and improving lives of older people and their
families. For more information on NIA and aging in general,
visit the NIA website
is one of the most common diseases of aging, occurring when
bone reabsorption by osteoclasts exceeds bone deposition
by osteoblasts. The disease afflicts 1 woman in 4
and 1 man in 40, causing more than 1.5 million fractures
a year at a cost exceeding $10 billion.
supplementation to prevent bone loss in post menopausal
women has been the subject of intense scrutiny. Since 1988,
43 studies have been published on the relationship between
calcium intake, bone mass, and bone loss. Results have been
confusing, in part because actual calcium intake cannot
be determined. In 19 of the 43 studies, however, the investigators
were able to control calcium intake, and in 16 of the 19,
calcium slowed or stopped bone loss.
reason for conflicting data is failure to segregate data
for women within 5 years of menopause. According to endocrinologist
Robert Heaney, during this period bone loss is due predominantly
to estrogen withdrawal, not to whatever calcium insufficiency
may also be present. In 12 of the 19 studies in which calcium
intake was controlled, women were excluded who were within
5 years of menopause; all 12 studies showed that calcium
conferred a significant benefit. A final problem
with clinical studies is that follow-up is usually too short
to provide meaningful data.
Reid et al. reported the results of their long-term (more
than 2 years) placebo-controlled study of calcium intake
and bone mineral density in 122 normal woman (average age,
58 years) at least 3 years after they had reached menopause.
Mean dietary calcium intake was 750 mg a day, and the supplemented
group received an additional 1000 mg elemental calcium (5.24
g calcium lactate-gluconate and 800 mg calcium carbonate,
formulated as an effervescent tablet).
control group received an identical-appearing placebo. Subjects
were evaluated 3 and 6 months after beginning therapy and
then every 6 months for 2 years. Bone densitometry (total
body, lumbar spine, and proximal femur) showed that calcium
supplementation had a beneficial effect on bone
loss that was consistent and statistically significant throughout
placebo group lost bone at a rate of about 1% a year at
most sites. On average, the rate of loss of total- body
bone mineral density was reduced by almost half (43%) in
the calcium group, and loss was eliminated entirely in the
trunk. The only adverse event was the development of a kidney
stone in one patient at 6 months. (Reid IR et al. N Engl
J Med. 1993; 328: 460-464.)
much calcium is enough to prevent postmenopausal bone loss?
The 1984 Consensus Conference on Osteoporosis recommended
a total intake of 1500 mg per day for women with estrogen
deficiency. This is about the average amount of calcium
required to keep a post menopausal woman in calcium balance.
This intake is probably two or three times that of most
adult women in the United States. The data from Reid et
al. indicate that a higher daily calcium intake -- 1750
mg total -- may be more effective for reducing bone loss.
And, as Heaney noted, studies suggest that it is never
too late to start treatment; reductions in fracture
rates can occur in as little as 18 months. Vitamin D levels
are commonly low in this age group, and supplementation
promotes calcium absorption. Preventing osteoporosis is
a worthy goal. A reduction of just 20% in the US hip fracture
rate would reduce the number of hip fractures by 40,000
to 50,000 annually, for an average saving of $1.5 to $2
studies have determined that the quality of the calcium
supplement, the times taken throughout the day, and adherance
to continued supplementation far outweigh the amount taken
om individual doses..
other words, if you take a high quality calcium supplement
several times throughout the day (not one mega dose per
day), and continue with this treatment indefinatly, your
benifits would be far greater then a hit or miss treatment.
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