|MadSci Network: Biochemistry|
Lisa, I know that high-protein diets put a strain on the kidneys in their attempt to excrete the excess waste matter that is the product of protein metabolism. I couldn't find a specific answer to your question, but I would guess that it is something like this. The kidneys basically filter out and keep the blood proteins and cells and "excrete" everything else, and then recover all the nutrients (glucose, vitamins, minerals like potassium and calcium, etc) from what goes through the filter except what they don't want, ie, urea and other waste products. Everything that is recovered is recombined with blood proteins and cells and put back into circulation. So the "loss" of things like urea, calcium, and potassium is passive and the recovery is active. I suspect that one of the things that happens when the kidneys are strained is that they operate at less than their usual efficiency and aren't as good as recovering the things like calcium that the body needs, but the passive loss of those things has nothing to do with how well the kidneys are functioning. Thus the loss of calcium stays the same but the recovery decreases, and overall you have calcium depletion. Again, this is a total guess on my part because I couldn't find any information on this sort of thing myself. This may be completely more work than you want to do, but you could call a local hospital or medical school and get connected to the renal/nephrology department and ask one of them as well.
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