Mayo Clinic finds vitamin D toxicity rare

Reprinted with the kind permission of Life Extension.
May 6 2015. The May 2015 issue of Mayo Clinic Proceedings reported the outcome of a retrospective population-based study that found little incidence of vitamin D toxicity among a large sampling of subjects over a ten year period.
For their study, family medicine expert Thomas D. Thacher and his associates utilized information obtained from the Rochester Epidemiology Project’s database—a medical record linkage system of Olmsted County, Minnesota residents. Of 20,308 25-hydroxyvitamin D [25(OH)D] test results available, 1,714 that documented levels greater than 50 nanograms per milliliter (ng/mL) were included in the current investigation.
Among subjects with 25(OH)D test results that were greater than 50 ng/mL, there were only four cases that were temporarily associated with elevated serum calcium levels (an indicator of possible toxicity) within the three month period before and after testing. “We found that even in those with high levels of vitamin D over 50 ng/mL, there was not an increased risk of hypercalcemia, or elevated serum calcium, with increasing levels of vitamin D,” stated Dr Thacher.
Another finding was a rise in the number of 25(OHD) test results that were higher than 50 ng/mL over the ten year period examined in the study. “We were surprised by that degree of dramatic increase in vitamin D levels,” Dr Thacher remarked.
In an accompanying editorial, vitamin D authority Michael F. Hollick, PhD, MD, asks whether the slight increase in mortality associated with higher 25(OH)D levels by some research might be attributable to lingering effects of chronic deficiency that preceded treatment with vitamin D rather than to increased vitamin D levels.
“The evidence is clear that vitamin D toxicity is one of the rarest medical conditions and is typically due to intentional or inadvertent intake of extremely high doses of vitamin D,” he concluded.

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