The Reminder is making its archives back to 2003 available on our website. Please note that, due to technical limitations, archive articles are presented without the usual formatting.
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: in the skeleton and teeth in the cells in the blood. Because calcium is so important, the body has a carefully regulated system to ensure that a good supply is always Ð and immediately Ð available. The body does this 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 Ð our 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 Òmaintenance crew.Ó 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 Ð 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.
