THE HEART OF THE MATTER
a special program of the National Emergency Medicine Association (NEMA) 

Week: 529.4 Guest: Dr. Joe Zerwekh, Univ. of Texas, Southwestern Medical Center at Dallas Topic: Sodium Encourages Osteoporosis Host: Steve Girard

NEMA: Today, we're with Dr. Joe Zerwekh of the University of Texas Southwestern Medical Center at Dallas. Doctor, I understand restricting the amount of sodium a post menopausal woman consumes helps battle osteoporosis.... how was this link discovered?

Zerwekh: Several years ago, when we were investigating some of the nutritional causes of kidney stone formation, we investigated the possibility that high dietary intake of sodium was promoting an increased loss of calcium in the urine.Then we began to wonder whether this loss of calcium might also represent the increased breakdown of the skeleton in order to maintain adequate calcium levels in the blood. And this indeed proved to be the case. In other words, if an individual eats a lot of salt, the amount of calcium that they lose from their body through urinary losses goes up, and in order to compensate for this loss, there is a release of para-thyroid hormone, which, as one of its primary mechanisms, is to stimulate the breakdown of skeletal tissue. And that acts to raise or to put calcium back in the blood to compensate for the calcium that was lost in the urine. So, if this continues, I think you can see that over a given period of time, there could be a substantial loss of skeletal mass.

But in the case of sodium induced loss, individuals don't want to cut back on their calcium intake, they've developed a habit of eating salty food, so they continue to use the salt shaker excessively, and as long as they do that, they're going to continue to lose excessive calcium in their urine, and this whole series of events will continue to transpire.

NEMA: Now, some people may say, "So, if increased sodium intake means the leeching of calcium from my bones, I'll just supplement calcium more heavily...or is there another complication in that reasoning?

Zerwekh: In general, that's a good idea, but you have to realize that some of the supplements that are out there may not provide an adequate amount of calcium that is lost from the urine. Secondly, the forms of calcium are going to provide different amounts of what we call bio-available calcium, and this is going to vary from individual to individual. Its probably a good idea to raise the calcium intake, particularly in any post-menopausal women. Their calcium intake should be in the neighborhood of 12 hundred to 15 hundred milligrams per day, both with supplements and dietary contributions. And many women are not that high, but the best bet would be to raise the calcium, and to reduce the amount of sodium in the diet.

NEMA: Dr. Zerwekh says sodium seems to cause calcium leeching particularly from the hips and ankles. And he advises women at risk for osteoporosis to watch the high levels of sodium which may be in canned goods like soups, and the so called convenient, pre-packaged meals. I'm Steve Girard.