What a paper, just when we are worrying about levels of 20 ng/ml being too high, along comes Southern California, Dr. Simran Bhandari, and his associates at Kaiser Permanente. Using a now defunct Nichols Advantage analyzer, the Kaiser folks asked a question that Nichols Advantage cannot answer, what is the best absolute vitamin D level? However, it is a great question.
What they found was remarkable, the crude odds ratio (risk) of being hypertensive was almost five times higher for those with 25(OH)D levels less than 15 ng/ml compared to those above 40 ng/ml. The same was true for renal function. However, as Nichols Advantage was used, all we can say is look at the differences, not the absolute levels. If you believe Nichols, you believe that 1,812 of 2,722 patients tested had vitamin D levels higher than 40 ng/ml. I doubt it, even in Southern California.
No U-shaped curve in Southern California, not even a suggestion of one. Of course these patients were tested between 2004 and 2006 so some were already on pure vitamin D, not vitamin D contaminated with retinol (cod liver oil). Too bad the authors couldn’t tell us more about the sample, like how many were taking vitamin D? Some of the Kaiser hospitals are in the forefront of vitamin D supplementation. Kaiser Permanente seems to know that vitamin D is the answer to those vexing medical care cost questions.
Bhandari SK, Pashayan S, Liu IL, Rasgon SA, Kujubu DA, Tom TY, Sim JJ. 25-hydroxyvitamin d levels and hypertension rates. J Clin Hypertens (Greenwich). 2011 Mar;13(3):170-7. doi: 10.1111/j.1751-7176.2010.00408.x. Epub 2010 Dec 22. http://www.ncbi.nlm.nih.gov/pubmed/21366848