Medicine For People!

December 2010: Vitamin D Update

The Headlines

"Expert Committee says very high levels of vitamin D recommended by doctors in testing laboratories are unnecessary and could be harmful!"

"Most people have adequate amount of vitamin D in their blood"

A new government report was released last week and the media ran with it. The medical media game of "Whack a Mole" has abandoned vitamin C, vitamin E, and estrogen. Now the game has moved on to the sunshine vitamin. What gives?

Why This New Report?

In recent years there has been a sea change in our understanding of vitamin D. Evidence has emerged that vitamin D plays a wide-ranging role in our immune system, spurring some people to take thousands of units of the supplement a day. As a result, the governments of the United States and Canada commissioned a report to determine what, if any, changes need be made in national policy regarding vitamin D. Vitamin D is added to different foods and sold as supplements, so governments need guidance on how to regulate this. Hence this report commissioned from the Food and Nutrition Board of the Institute of Medicine. The report runs about 1000 pages. I focused on the

  • Initial Summary
  • Vitamin D portion of the Tolerable Upper Intake Level chapter and
  • Implications of Special Concerns chapter

Time allows me to address only the vitamin D aspect of this story, not the calcium issues which they addressed as well.

Goal of the Report

The report had as one goal the establishment of a recommended dietary allowance or RDA which meets the needs of 97.5 percent of the population, or 39 out of 40 people. The committee was also tasked with establishing a Tolerable Upper Intake Level, above which the potential for harm increases. This is a level that our government could publicize that would apply to un-monitored, free living people who might take that recommendation and follow it for a lifetime without further thought or attention to changes in the guidelines.

If I may set the scene then, this committee was tasked with coming up with numbers that would be bulletproof for the foreseeable future and cause no embarrassment to the government agencies involved. Those who commissioned this report and the people preparing it knew that if there was any advice that led to headlines in the future, then big heads would roll. Errors had to be on the side of caution. A similar report prepared over a decade ago by the same committee arrived at a recommended daily allowance of 200 units, 1/3 of what they chose to be the minimum this time. They lost no points for being too low. Such is nutritional politics.

Methods Used

They did not undertake new research, but rather reviewed hundreds of papers and studies looking at the relationship of vitamin D to bone health, cancer, heart disease, diabetes, kidney stones, and many other conditions. Upon evaluating all this, they decided that the only rock solid, beyond-a-doubt benefit of vitamin D that they would accept is for bone strength.

The committee did not accept the flood of reports of effects of vitamin D tissues other than bone. They noted that the results were sometimes conflicting, that the studies were not as large as they would like, the methodology was imperfect, and that the benefits might not extend to an entire population.

Setting Blanket Levels for Vitamin D

Once they made the decision to use only bone health as their measure of vitamin D adequacy, they looked at how much vitamin D it took to maintain bone health. They decided that a blood level of 16 ng/ml of vitamin D would meet the needs of half the population and that 20 ng/ml would meet the needs of most of us. Therefore they set their minimum acceptable blood level of vitamin D at 20 ng/ml and looked at the amount of supplemental vitamin D it would require to produce that. This comes out to 600 international units of vitamin D daily for adults, and this they set as the RDA for adults. Time does not permit me to critique their hundred page analysis.

In terms of safe upper levels of vitamin D intake, the committee again took an extremely conservative stance. Since we can create vitamin D with exposure to sunlight and the ability to do this varies greatly among individuals, the team discounted vitamin D from the sun. They seemed to accept all published reports of toxicity from vitamin D uncritically. While they noted that "Most reports suggest that the toxicity threshold is between 10,000 and 40,000 IU of vitamin D per day" they ended up revising that down to 5000 IU daily, then took 80% of that,4000 IU daily, as a tolerable and safe level under any conceivable condition.

Responsible Authorities Differ

Most authorities regard the American Society for Nutrition as the leading nutritional authority in North America and their publication, the American Journal of Clinical Nutrition (AJCN) as the leading peer-reviewed journal in the field of nutrition. In the most recent AJCN review of vitamin D requirements ("Estimation of the dietary requirement for healthy adults" published in 2008 Vol 8, pages 1535-42) they reported a daily minimum requirement of between 300 and 1600 IU daily, the variance attributed to food choices and sunlight exposure. This recommendation is for people who are judged to be vitamin D sufficient. Someone deficient in vitamin D will require more than the recommended daily allowance to get back up to normal.

The most recent AJCN consideration of vitamin D toxicity1 concluded that 10,000 IU daily is a safe upper limit for adult intake of vitamin D.

A Difficult Task

Everyone in nutritional research acknowledges that it is difficult to isolate the effects of a single nutrient among the many nutrients we consume each day, and this report echoes that. As well, individuals synthesize the various forms of vitamin D at different rates depending on sun exposure, age and kidney function. Finally, vitamin D, calcium, and probably other nutrients interact with each other so requirements for one are influenced by the amount of the other that a person is taking.

Finally, the authors are not giving advice to physicians treating real people, they are setting public policy. In a medical practice we can't rule out the role of vitamin D in preventing disease besides osteoporosis. There are vitamin D receptors in bone, potential cancer cells, brain, skin, and several elements of the immune system. Those receptors have functions. Attention to this emerging information allows us to improve health and well-being on an individual basis.

Not the Last Word

One of the major areas of contention over this report will be their conclusion that the only proven benefit of vitamin D is to bone, and that a 20 ng/ml blood level satisfies that need. This they cover in a 187 page analysis that would take many weeks to analyze. I know two authorities who are probably deep into that task already. One is Michael F. Holick, the author of the vitamin D chapter in the standard textbook of nutrition; "Modern Nutrition in Health and Disease" (edited by Maurice Shills of Cornell University) and the other is Reinhold Veith PhD, director of the Bone and Mineral Laboratory at the University of Toronto. There will be debate over the next year or two about the findings and conclusions of this report and I would especially pay attention to comments from these two.

Some take home points

  • This report involves no new research, merely analysis of current research to set government policy in very specific arenas.
  • Journalists catch readers when they have an "angle" on a story, so the temptation is to either sensationalize or discredit this report. Nature is not so simple.
  • As time passes, other workers in the field of vitamin D in human nutrition will critique some of the findings, judgments, and conclusions of this report, just as happened with the large study of estrogen some ten years ago.
  • To the extent that this report advances our current understanding of vitamin D, we can only welcome that. The report does raise the RDA from 200 to 600 IU daily, itself acknowledging our changing understanding over time.

My Recommendation

Don't experiment with high doses of vitamins. Unless your doctor suggests otherwise, for maximum safety stay within the recommendations given in this report.

A Holiday Wish

All of us at the Monroe Street Medical Clinic wish you a happy holiday season. We thank you for your support of our clinic.

For more information on Vitamin D, check out our previous newsletters:

September 2009
November 2009
November 2008
February 2004
March 2004


Full text. Hathcock JN, Shao A, Vieth R, Heaney R. Am J Clin Nutr. 2007 Jan;85(1):6-18. Council for Responsible Nutrition, Washington, DC 20036-5114, USA.

The objective of this review was to apply the risk assessment methodology used by the Food and Nutrition Board (FNB) to derive a revised safe Tolerable Upper Intake Level (UL) for vitamin D. New data continue to emerge regarding the health benefits of vitamin D beyond its role in bone. The intakes associated with those benefits suggest a need for levels of supplementation, food fortification, or both that are higher than current levels. A prevailing concern exists, however, regarding the potential for toxicity related to excessive vitamin D intakes. The UL established by the FNB for vitamin D (50 microg, or 2000 IU) is not based on current evidence and is viewed by many as being too restrictive, thus curtailing research, commercial development, and optimization of nutritional policy. Human clinical trial data published subsequent to the establishment of the FNB vitamin D UL published in 1997 support a significantly higher UL. We present a risk assessment based on relevant, well-designed human clinical trials of vitamin D. Collectively, the absence of toxicity in trials conducted in healthy adults that used vitamin D dose > or = 250 microg/d (10,000 IU vitamin D3) supports the confident selection of this value as the UL.



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Medicine for People! is published by Douwe Rienstra, MD at Port Townsend, Washington.