Robert P. Heaney, MD, Creighton University
Comments on Kidney Stones & Vitamin D
We frequently get questions based on a 'myth' that vitamin D causes kidney stones. I asked Dr. Heaney to provide us some information that we could share with all of us health conscious people as well as to the clinicians in our audience. Please feel free to copy/distribute to all! We need to get the word out about the facts! (That's why we have a section called 'D*Facts' as well.) Have a super lovely day.
Dr. Heaney's Comments:
- Kidney stones are of many types and have many causes.
- The most common types in the US are calcium oxalate stones.
- The stone should be analyzed so as to determine the approach to treatment.
- Whatever the stone type, stone formers have a defect in kidney production of a solution stabilizer, normally secreted into the urine. This keeps the commonly supersaturated urine from forming precipitates (which then aggregate into stones).
There are two basic approaches indicated in most cases.
- One is to drink large amounts of water each day to keep the urine diluted
- The second is to reduce the urine content of components that form precipitates. For example, if the stone is a urate stone, medicines will be prescribed that reduce the body's production of uric acid. Or if the stone is calcium oxalate, large quantities of calcium should be ingested to block absorption of oxalic acid from the intestinal contents, thereby reducing the amount of oxalate that will have to be excreted through the kidneys. While high calcium intake sounds counter-intuitive, there is a solid scientific base for the recommendation, and persuasive clinical trial data showing that it works. Placing patients on low calcium diets will actually double the risk of having a second stone.
- There are several other approaches that might be taken, but the foregoing hit the main points. It's important to remember that the basic defect (absence of a solution stabilizer) persists, so whatever strategy works will have to become permanent.
- Vitamin D, in doses producing desirable serum levels of 25(OH)D (40-60 ng/ml or 100-150 nmol/L), does not adversely affect any of the components of this system