If you are healthy, your body automatically determines how much dietary calcium your bones should use, how much should remain in your blood and how much you should excrete. If you have low kidney function, your body has a harder time making such determinations. All too often, calcium is leached from the bones, which has dangerous consequences. You can control this problem by working with your nephrologist and diligently following whatever dietary suggestions he makes.
Phosphorus
If your kidney function is low, your phosphorus levels tend to creep up. High levels of phosphorus leach calcium from the bones. This can permanently weaken bones and cause calcium deposition on blood vessels, organs and other tissues. Nephrologists recommend low-phosphorus diets to control this problem. They often prescribe some type of phosphorus binder, as well. Phosphorus binders are a type of drug that you take with meals. They bind to phosphorus in the gut and cause it to be excreted before it gets into the bloodstream.
Parathyroid Hormone
The parathyroid glands are also involved in regulating calcium levels. These four glands in the neck secrete parathyroid hormone, or PTH, into the bloodstream. In healthy people, PTH regulates the balance of calcium in the bones and in the blood. Nephrologists routinely measure PTH levels in kidney patients because high levels of PTH leach calcium from the bones. A drug called cinacalcet hydrochloride can treat high PTH levels.
Vitamin D
The kidneys convert the vitamin D you get from sunlight and food to calcitriol, also known as 1,25-dihydroxyvitamin or calciferol. Scarred kidneys are unable to perform this function, so calcitriol levels often drop, which causes PTH levels to soar, which in turn causes calcium leaching from bones. Specially formulated renal vitamins contain calcitriol, which helps prevent this problem.
Managing Calcium Issues
While calcium and bone health are not issues if you have normal or nearly normal kidney function, managing this problem is a major aspect of taking care of people as they approach renal failure. In addition to maintaining bone health, doctors try to prevent calcium deposits. Not only do calcium deposits in cardiac tissue cause heart attacks, but deposits in the joints can be extremely painful, as well.
References
- National Kidney & Urologic Diseases Information Clearinghouse; Vitamin D and Chronic Kidney Disease; February 2009
- Davita: Phosphorus Binders (Phosphate Binders) and the Dialysis Diet
- "Kidney International"; An Introduction to Phosphate Binders for the Treatment of Hyperphosphatemia in Patients with Chronic Kidney Disease; E.A. Friedman; July 2005
- DaVita: Vitamin D and Chronic Kidney Disease
