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Bone density, also known as bone mineral density, is the measurement of density of minerals, such as calcium, present in an individual's bones. It is typically measured in units of matter per area of bone. Bone density tests are often taken to determine the strength of an individual's bones and to determine the risk of various bone density disorders, such as osteoporosis. It should be noted that such tests do not give an actual density, as density is measured in mass per volume; these tests merely measure the amount of specific substances in a given area of bone.
The strength of one's bones is closely related to his bone density. Those with low bone mineral density tend to have brittle bones, while those with high bone mineral density tend to have strong bones. Much of the formation of bones takes place in one's childhood and teen years, so it is important to ingest the right nutrients from a young age. Low density can lead to a variety of unpleasant problems; bones can become brittle and break much more easily. It is particularly important for those who lead very active lifestyles to maintain healthy bone density.
A common condition called osteoporosis occurs when one's bone density decreases. It leads to a great increase in the chance of bone fractures. The disease is much more common in women than in men, but it can and does appear in men. The disease is preventable; the combination of a healthy diet, active lifestyle, and vitamin supplements, such as vitamin D and calcium, can greatly reduce the risk of osteoporosis. Those who have osteoporosis must do their best to avoid falling, as their bones tend to be quite brittle.
Bone density can be measured through a bone mineral density test, which can be taken in many different ways. X-rays and ultrasounds are two methods commonly used to measure one's bone mineral density. The process of measuring bone mineral density is known as densitometry.
Bone density naturally declines as people age. The production of new bone slows down and can't keep up with the rate at which old bone breaks down. Bones become thinner and more porous as their density decreases. They tend to lack important minerals, such as calcium, that keep them strong. This greatly increases the chance of breakage; as such, people who are advanced in age must be careful to prevent falling and breaking their thin and brittle bones.
@Kat919 - I'm glad you pointed that out. It's another reason why we need to keep young people moving, since they are building their bones at that age. Get them off the couch and into whatever they like - running, karate lessons, etc.
A friend of mine who is a vegan told me something interesting that people might not realize. Apparently, eating high levels of animal protein (as from meat and dairy) causes your body to *lose* more calcium in your urine than you otherwise would. The calcium recommendations from the USDA are very high to compensate for that.
So vegans and vegetarians may not need as much calcium as omnivores, and calcium from vegetable sources is fortunately just as
well absorbed by the body. If you have a teenager who goes through one of those vegan phases (and you never know, it could stick like it did for my friend), educate him or her about broccoli, dark leafy greens, etc. to make sure s/he gets enough calcium.
Fortunately, people with active lifestyles - those who most need bone density - are already at an advantage in maintaining their bone mass density.
You see, it's not just a matter of eating enough calcium, it's also about getting certain kinds of exercise. Weight-bearing exercises (anything in which you're on your feet, from tennis to dancing to walking) and strength training will help encourage your body to maintain strong bones. If you are sedentary, your body will think that you do not need strong bones and that trying to maintain them would be a waste of valuable resources.
So after you take your calcium supplement, head out the door for a walk, pick up a resistance band, or put on your favorite song.
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