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Calcium: An essential element for life
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.
In the body, calcium
is found in three places:
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 this in three ways:
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It absorbs calcium directly from the food we eat.
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It takes calcium from our bones if there is not enough available. When
this happens, the bones become less dense and more fragile.
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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
"maintenance crew." 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.
Learn more about nutrition and
osteoporosis:
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