As chronic kidney disease becomes more advanced, nutrition becomes a problem as the kidneys lose the ability to remove excess nutrients from the blood. For example, potassium, phosphorus, calcium and vitamin A levels often elevate. When your system is this out of balance, taking calcium and vitamin D supplements can have unintended consequences. Always consult your nephrologist before taking any supplement if you have kidney disease.
Vitamin D
The vitamin D you get from your diet or from the sun undergoes two conversions before you can use it. Enzymes in the liver convert vitamin D to 25-hydroxyvitamin D, also known as calcidiol and 25-hydroxyvitamin D. Enzymes in the kidneys convert 25-hydroxyvitamin D to 1,25-dihydroxyvitamin D, also known as calcitriol and 1alpha,25-dihydroxyvitamin D. The kidneys of people with very poor kidney function are often unable to perform this second conversion. Consequently, they have high levels of the vitamin D precursor, but not the biologically active vitamin.
Calcium
Kidney patients often have elevated levels of phosphorus in their blood, which leaches calcium from the bones. This can cause serious bone disease in kidney patients. Serum levels of calcium increase when it is leached from the bone, which in turn, causes calcium deposits in blood vessels, muscles and organs. Nephrologists try to control this by prescribing phosphorus binders and recommending a low-phosphorus diet.
Recommendation
You should never take calcium or vitamin D without consulting your nephrologist first. If your 25-hydroxyvitamin D levels are low, your nephrologist might prescribe a special form of biologically active vitamin D. However, since vitamin D is essential to calcium uptake, nephrologists often intentionally ignore low levels 25-hydroxyvitamin D because correcting this problem could cause other problems related to high calcium levels.
Renal Vitamins
Renal vitamins are specially formulated to address the unique needs of kidney patients. These vitamins contain small amounts of needed vitamins and minerals, while omitting vitamin D, calcium, potassium, phosphorus and vitamin A. End stage patients need such a supplement because they are often malnourished and suffer from muscle wasting. Talk to your nephrologist and see if these vitamins are appropriate for you.
References
- Linus Pauling Institute; Vitamin D; Jane Hidgon; March, 2004
- DaVita; Calcium and Chronic Kidney Disease; Sara Colman
- DaVita: The ABCs of Vitamins for Kidney Patients
- DaVita: Vitamin D and Chronic Kidney Disease
- National Kidney & Urologic Diseases Information Clearinghouse; Chronic Kidney Disease-Mineral and Bone Disorder; September 2010
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