Sunday, April 8, 2007

Calcium and Your Bones - Mini Medical School

One of my patients said she heard calcium supplements are not that important in post menopausal women. She couldn't be more wrong. Read this and you will be as informed as most physicians about calcium and bone health.

2/3 of our bone mass is made up of the mineral calcium phosphate. Because bone is alive, there is constant removal and replacement of calcium, called bone remodeling. The parathyroid gland secretes a hormone called PTH and that determines the amount of calcium that gets pulled from the bone into the bloodstream. When we have enough calcium in our bloodstream, it decreases PTH and more is absorbed to preserve bone. Vitamin D is also important to absorption of calcium into the bone mass. Inadequate amounts of calcium and Vitamin D cause reduced bone mass and weakness leading to fractures. Reduced bone mass is called osteopenia and severe bone loss is called osteoporosis. Have you noticed that older people seem to shrink with age? That is largely because the skeletal structure is collapsing due to weakened bone mass.

There is no scientific doubt about the importance of adequate calcium to build and preserve skeleton. But calcium alone does not prevent bone loss. Exercise, adequate protein and Vitamin D are also needed - especially after midlife.

We need to take in 1000mg/day of calcium up to age 50 and 1200-1500mg/day after that. Calcium is not well absorbed from the diet and we lose calcium in our urine and sweat. Calcium intake in North American post menopausal women is 550-650 mg/day below the recommended amount. At low intakes, bone mineral is being lost. At adequate intakes the bone is at steady-state, maintaining its integrity. However, at higher intakes, no further bone is built. We don't store calcium for later use by the skeleton. Since most adults don't get enough calcium from our food, if you are going to take any dietary supplements, calcium is the most important.

Despite the huge body of scientific evidence about calcium and bone strength, one study showed only 23% of physicians recommended calcium to patients with osteoporosis. The bisphosphonate drugs that are used to treat osteoporosis (Fosamax, Actonel and Boniva) all used supplemental calcium in the studies that showed effectiveness. Without supplemental calcium, we don't know if they work at all. Other studies showed 3/4 of patients taking bisphosphonates are not taking sufficient calcium supplements. The US Surgeon General said " Calcium has been singled out as a major public health concern today because it is critically important to bone health, and the average American consumes levels of calcium far below the amount recommended for optimal bone health."

Calcium in our diet comes from milk, hard cheese, yogurt, cottage cheese, broccoli, Chinese cabbage (bok choy), green leafy vegies, dried fruits, nuts and seeds. For an extensive list of calcium in foods go to food pyramid

The best calcium supplement to take is one that is easy and inexpensive. Calcium carbonate delivers more calcium than calcium citrate and taking with food also helps with absorption. Start slow with 500mg a day and add until you reach the recommended dose. For best absorption it is better to take calcium twice a day but all at once is better than none at all. There are some drugs that may interact with calcium and cause altered blood levels of the medication and they are:
*digoxin (a heart medication)
*levothyroxine (a thyroid pill)
*phenytoin (for seziures)
*thiazide (a common diuretic)
*glucocorticoids (cortisone)

For more detailed information on types of supplements go to calcium supplements

The Surgeon General said "The gap between what we know about calcium and its application in the community remains large and needs to be closed". Now we are narrowing that information gap. A calcium supplement may help make the difference in how healthy your bones are as you age.


Anonymous said...

Thanks, for writing on this. I do take calcium but not enough which I knew and you answered some of my questions on the amounts for the different ages. Valuable, informative article.

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