Rethinking what we know about optimal vitamin D dosing.
There is no debate about the any benefits of vitamin D. The “sunshine vitamin” supports muculoskeletal system by governing calcium for optimal bone strength and density, in addition to enhancing muscle tone. Vitamin D also supports a robust immune response, reduced levels of certain inflammatory cytokines, and reduced risk of heart attack.
Vitamin D has even been shown to support the production of serotonin in the brain by activating the enzyme tryptophan hydroxylase-2.
The Institute of Medicine (IOM), part of the National Academies of Sciences, Engineering, and Medicine, citing evidence on bone density and the reduction of falls in the elderly, recently set recommendations of 600 international units (IU) of vitamin D for daily intake, increasing the dose to 800 IU for those over age 70.
Calculations by researchers at the University of California, San Diego, and Creighton University have shown that these doses are only about one-tenth those needed to support vitamin D levels linked to reducing incidence or risk of diseases related to vitamin D deficiency.
How did the IOM get vitamin D dosing so wrong and how does the clinician make a more appropriate suggestion?
To begin with, the current vitamin D recommendations are inadequate due to mathematical error.1 There are two issues with respect to the IOM stance on vitamin D requirements: The IOM chose 20 nanograms per milliliter (ng/ml) of serum concentration of 25-hydroxy vitamin D to be an adequate level, but vitamin D researchers now believe that’s too low.
Most laboratories that perform vitamin measurements use a value of 30–100 ng/ml as the normal range. The IOM appears to indicate that 20 ng/ml is the beginning of adequacy, a level that the vitamin D community feels is insufficient.
In addition, to maintain a level of 20 ng/ml, the IOM says you need to take 600 IU a day up to age 70, and 800 IU if you’re over 70. But research indicates this is wrong, and likely due to the result of a mathematical error.
Taking another look
In 2014, two investigators from the University of Edmonton published a paper in the journal Nutrients, in which they showed that the IOM had made a calculation error in defining the intake needed to reach and maintain a vitamin D level of 20 ng/ml.2 Had the IOM calculated it correctly, the recommended dietary allowance (RDA) would have been 10 times greater.
The RDA is the intake considered necessary to meet the nutritional needs of 97.5 percent of the population.
Nearly half the people who get 600 IU of vitamin D a day do not reach the 20 ng/ml level, and thus are deficient. The Edmonton investigators, using the same studies on which the IOM had based its calculation, determined an intake of 8,895 IU per day would be necessary to achieve 20 ng/ml in 97.5 percent of the population. Robert Heaney, MD, is a prominent vitamin D researcher, and his group Grassroots Health has been compiling a vitamin D research database to determine more appropriate dosing levels for vitamin D. Using the same set of IOM studies, Heaney’s group found that 7,000 IU would bring 97.5 percent of people above 20 ng/ml. As a clinical endocrinologist, Heaney has spent much of the last 50 years doing clinical research, most of it in the field of vitamin D, working on quantifying the level of vitamin D intake needed for optimal health.
Until the IOM’s error resulted in an inadequate vitamin D dosing recommendation, 20–30 ng/ml levels were considered insufficient. For some reason, now the IOM feels that 20 ng/ml should be the new minimum range.
Fortunately, as a doctor you are free to disregard bureaucratic confusion with regard to vitamin D dosing.
Given the absence of evidence that vitamin D levels greater than 30 ng/ml are harmful, and given the many studies showing 40–60 ng/ml as being more physiologically ideal, you are free to recommend more clinically relevant doses.
In general, the vitamin D community of clinicians suggests that 4,000–5,000 IU daily is appropriate dosing, with an upper limit of 10,000 IU. Many physicians recommend a 50,000 IU weekly dose for a few months to bring up levels in patients who are beneath 20 ng/ml. And routine measurement of serum 25-hydroxy vitamin D is an efficient way to assess an individual’s response to the dose you recommend.
Jolie Root is the senior nutritionist and educator for Carlson Laboratories in Arlington Heights, Illinois. She travels throughout North America attending medical conferences, lecturing, and educating the public about the role of nutrition in integrative medicine. Root can be followed on Twitter @jolieroot, and contacted through jolieblogs.com.
1 Creighton University. Recommendation for vitamin D intake was miscalculated, is far too low, experts say.” ScienceDaily. http://www.sciencedaily.com/releases/2015/03/150317122458.htm. Published March 2015. Accessed August. 2015.
2 Veugelers PJ, Ekwaru JP. A Statistical Error in the Estimation of the Recommended Dietary vitamin D. Nutrients. 2014;6(10):4472-4475.