• Calcium Q & A • calcium supplements • choices in calcium • calcium-rich foods •
Calcium is crucial to maintain life. 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. Calcium is found in three places in the
body, the skeleton and teeth, cells and blood. Because
calcium is so important, the body has a carefully
regulated system to ensure that a good supply is always-
and immediately-available. The body does it in
three ways: it absorbs calcium directly from the
food we eat, it takes calcium from our bones if there is
not enough available. When this happens, the bones
become less dense and more fragile. It slows down
the amount of calcium that leaves the body in the urine
by returning some to the blood stream where it remains
available to organs and cells. The main goal of
good calcium nutrition is to maintain an adequate supply
so that our bodies do not have to dip into our only
calcium reservoir- our bones.
The role of
calcium in building stronger bones:
In childhood, calcium is necessary
to grow a healthy skeleton to support a growing body. By
age 20 in men and age 16 in women, bones typically stop
growing in length and we are almost at our peak bone
mass. The density of our bones at this point depends a
lot upon our calcium intake as children and teenagers.
The greater this peak bone mass, the less likely our
bones are to become porous and fragile later in life.
Bone 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 foundations
of a building over time.
In our bodies, there are two groups of
specialized cells that perform the work of a
Osteoclasts excavate any areas of
crumbling or weakened bone and then osteoblasts fill in
the crevices with material that calcifies to form new
bone. This two-part process is called bone remodeling,
and is completed every three to four months in a healthy
young adult. As we age, the two groups of cells that
form the maintenance crew become less efficient in
working together - the osteoclasts remove old bone
faster than the osteoblasts are able to rebuild it. In
addition, calcium, like many nutrients, is absorbed less
effectively as we age. In people who have relatively
healthy bones, adequate calcium intake can help the
remodeling process stay balanced. Studies of older
adults show that adequate calcium intake can slow bone
loss and lower the risk of fracture.
Your body needs calcium.
If this is your age,
then you need this much calcium
each day (mg).
|0 to 6 months
|6 to 12 months
|1 to 3 years
|4 to 8 years
|9 to 18 years
|18 to 50 years
|Over 50 years
There are some
things which interfere with the absorption of calcium:
interferes with calcium absorption
Fiber contains phytic acid, which
combines with calcium in the intestines and
forms a compound that can't be absorbed
extremely high protein levels
increase urinary excretion of calcium
||increases the amount of urine you
excrete--which also increases loss of
also increases urinary excretion of
Oxalates and oxalic acid
compounds found in green leafy
vegetables--unite with calcium during
digestion and turn it into insoluble salts
Calcium is so demanding that it
refuses to work in the presence of some of the most
common components of the traditional healthy diet.
Certain kinds of fiber, for example, bind to the
mineral and blocks its absorption. Excess protein
also appears to interfere with calcium uptake and
can actually increase calcium loss.
Often the very foods that would seem
to be good calcium sources also contain substances
that keep you from absorbing the calcium they
contain. Spinach, for example, like other leafy
green vegetables, is high in calcium, but it also
contains high levels of oxalic acid, a substance
that interferes with calcium absorption. The result
is that your body doesn't get much of the calcium
in spinach at all.
Because most multivitamin supplements
recommended for women contain iron, which inhibits
calcium, you should take your multivitamin and your
calcium supplement at separate times of the day.
Calcium is best absorbed if consumed
in split doses throughout the day. Generally, our
bodies can only absorb about 500 mg of elemental
calcium at a time.
Aluminum-containing antacids, iron
supplements and some prescription medications will
interfere with absorption and retention of your
calcium supplement and vice versa.
Consult with your doctor about the possibility of
such an interaction.
Because calcium is so
important, the body has a carefully regulated system
to ensure that a good supply is always — and
immediately — available when needed.
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. When this
happens, the bones become thinner and more fragile.
It slows down the amount of calcium that leaves the
body in the urine by returning some to the blood
stream where it remains available to organs and
Phosphorus is a mineral people get from eating
protein rich foods such as meat and milk. Some soft
drinks, such as colas, also contain phosphorus.
While phosphorus is needed to form bones and teeth,
medical studies have shown that too much phosphorus
in the diet may upset the calcium balance in humans.
A good guide is not to go over twice the RDA of
protein, and to limit the intake of carbonated
Fiber should be part of a healthy diet. There are
certain types of fiber that can affect the amount of
calcium the body absorbs. Rhubarb, spinach, chard,
and beet greens contain oxalate, which may decrease
the absorption of calcium. Phytic acid, found in
wheat bran, combines with calcium and also decreases
its absorption. Fiber, however, is very helpful to
the digestive tract, so it is important to balance
the level of calcium intake with the amount and type
of fiber in the diet. A diet containing up to 35
grams of fiber per day should be adequate for
healthy bowel movements, without adversely affecting
- Caffeine increases the loss of calcium through
the kidneys and intestines. While a moderate amount
of caffeine per day (300-400 mg) has only a small
effect, more caffeine may cause a much greater loss
of calcium. Therefore, avoid drinking more than
three cups of regular coffee or other high caffeine
beverages a day.
- Excessive alcohol intake may lead to loss of
calcium in the bone. Poor nutrition is often related
to abuse of alcohol. It has also been shown that
alcohol has a toxic effect on the formation of bone
cells. Do not have more than one or two drinks per
day. One drink would be 12 oz of beer, 5 oz of wine,
or 1.5 oz of 80 proof distilled spirits.
- Lifestyle can have an effect on the risk of
developing osteoporosis. Cigarette smoking increases
bone loss, and it may cause lower estrogen levels.
Regular exercise, including moderate weight-bearing
exercise, helps prevent bone loss and increases the
total amount of bone in the body. This is especially
important for the elderly who tend to become
sedentary. Examples of weight-bearing exercises
include walking, cross-country skiing, jogging,
aerobic dancing, and weight-training. The use of
estrogen replacement therapy is very helpful for
women who are no longer producing estrogen. Estrogen
replacement must be prescribed by a physician.
- Food sources of calcium include milk and dairy
products, which are the best sources of absorbable
calcium. About 25% to 35% of the calcium in dairy
products is absorbed in normal healthy people. Dark
green leafy vegetables also contain moderate amounts
of calcium, but their content of oxalate and fiber
may cause less of the calcium to be absorbed. Whole
grain flours contain more calcium than milled white
flours; however, whole grain flours contain more
fiber and phytic acid. Fish and tofu (processed with
calcium) are also good sources of calcium. Foods
such as orange juice, breakfast cereals, breads,
milk, and yogurt are often fortified with calcium.
Product labels should be checked for the amount of
calcium the foods contain.
- Calcium supplements may be necessary to get
adequate calcium intake. A physician or registered
dietitian should be consulted about the need for
calcium supplements. Several different forms of
calcium supplements are available. Calcium carbonate
is generally recommended because it contains the
highest percentage of absorbable calcium, 40%.
Calcium citrate is 21% calcium; calcium lactate is
13%; and calcium gluconate is only 9% calcium. Bone
meal and dolomite are not recommended because they
may contain toxic substances such as lead, mercury
and arsenic. Chelated calcium is expensive and has
no advantage over other forms. Long-term ingestion
of excessive amounts of calcium can lead to
unhealthy side effects, but taking 1000 mg to 2000
mg of calcium a day should not produce any serious
more calcium better?
- If you consume more calcium than
recommended, there is no proof that it
will benefit your bones.
- High calcium intakes consumed on a
regular basis may be harmful. It is
important to get your daily recommended
daily calcium and not to consume more
than 2500 milligrams of calcium per day.
The adverse effects of excessive calcium
intake may include high blood calcium
levels, kidney stone formation and
taking too much
- has been associated with a decreased iron
absorption, with the possible side effect of anemia
- will interfere with the absorption of
zinc--important for both bone and immune system
- may interfere with the synthesis of vit K which
is not only important for appropriate blood
clotting, but also plays a key role in bone health
- can cause kidney disorders in susceptible
people, if you have a history of kidney stones, make
sure your doctor knows this before you start a
regimen of calcium supplements
- will block the uptake of manganese and interfere
with the absorption of magnesium, which is also
important for bone health