References

This is an area that is changing rapidly, but with many redundant articles and misleading or unsubstantiated claims. Priority has been given to articles that are credible and provide useful links to academic references.

Further reading

An excellent and credible review series on vitamin D was published in The American Journal of Clinical Nutrition in December 2004.  This remains an excellent starting point for further study.  It is accessible for free online and importantly has active links to more recent related articles.  I recommend starting with these articles from that series.   

Hector F DeLuca
Overview of general physiologic features and functions of vitamin D
Am J Clin Nutr 2004 80: 1689S-1696S. [Abstract] [Full Text]

Robert P Heaney
Functional indices of vitamin D status and ramifications of vitamin D deficiency
Am J Clin Nutr 2004 80: 1706S-1709S. [Abstract] [Full Text]

The National Academy of Science Dietary Reference Intakes for Calcium and Vitamin D 2010 is a 1016 page report that deserves credit for containing reviews, assessments and references that serve as a good introduction to many aspects of vitamin D and its role in human health.

** Please read the introduction BEFORE drawing any conclusions from the summary.
The report is available for free review or download at:

http://www.iom.edu/Reports/2010/Dietary-Reference-Intakes-for-Calcium-and-Vitamin-D.aspx

Some personal comments/editorial: 

There were constraints within which the committee was required to respond.  The recommended vitamin D doses are expected to prevent overt bone disease (but not necessarily other conditions) in the general population and expected to be considered safe if ingested over long periods of time.  The recommendations are not adequate for high risk persons or persons with specific conditions. 

It should be noted that concern was also voiced that many adult females may be ingesting calcium in higher than healthy amounts.

Supporting comments and references which you are not necessarily expected to find of interest:      All references are from:  Dietary Reference Intakes for Calcium and Vitamin D Food and Nutrition Board A. Catharine Ross, Christine L. Taylor, Ann L. Yaktine, and Heather B. Del Valle, Editors PREPUBLICATION COPY: UNCORRECTED PROOFS

The 2010 report was prepared during a period when the explosion of information about and public attention to vitamin D lacked cohesive understanding, and was often misrepresented and exploited by commercial and pseudo-authoritarian sources.

It was fair and important that the committee restate the concern that the bulk of information available about vitamin D would indicate that a lack of adequate vitamin D is harmful to many organ systems, but that the concept of “more is better” is not well supported and that very large amounts may be harmful.

Having said that, the current summary findings of that report, and more disappointingly many quickly published reviews, poorly represent the information available in the report.  In addition there is a great deal known about vitamin D and the committee seems to have been constricted regarding the recommendations they were  willing or allowed to put forward.

The report was developed using a risk assessment model.  The chairperson takes pains to point out in the introduction to the report.  “Such a framework is not one that committee members would naturally have been familiar” (ix) and recommendations were meant to address improving “the health of the general population of the United States and Canada - they provide recommendations for adequate and safe daily intakes of nutrients consumed over many years, possibly a lifetime, not just for days, weeks, months, or a year.”  (x)  The recommendations are not targeted to persons at high risk or with specific medical conditions.   And recognize only measures related to bone health. (S-3) 
Only data on osteomalacia was used to support recommended target levels.  (S-8)  (Very conservative intake is defended by the statement “The ULs for vitamin D were especially challenging because available data have focused on very high levels of intake that cause intoxication and little is known about the effects of chronic excess intake at lower levels.” (S-8))

Worthy of mention is another overlooked remark by the committee

“However, when supplement use was taken into account (United States only), women at the 95th percentile of calcium intake appeared to be at risk for exceeding the UL. The data underscore the possible need to modestly increase calcium intake among older girls; among older women, a high calcium intake from supplements may be concerning.“  (s-9) 
(As an introduction for further reading I recommend - Heaney RP. Phosphorus nutrition and the treatment of osteoporosis. Mayo Clin Proc 2004;79:91-7.) ... http://www.mayoclinicproceedings.org/article/S0025-6196%2811%2963261-8/abstract http://www.mayoclinicproceedings.org/article/S0025-6196%2811%2963261-8/fulltext

In summary

The current report attempts to draw together a very wide, incomplete, sometimes inconsistent and often not understood body of data.  Much of this data is epidemiological.  Such information can suggest associations, but not prove causality.  It ends with a statement regarding the need for more and higher quality data. 

An oversimplified conclusion would be:

Vitamin D is important for the development or regulation of many tissues, most not having anything to do with calcium regulation.  We don't know enough about either calcium or vitamin D and we should know more. 

Given the constraints within which the committee was required to respond, the recommended vitamin D doses are expected to prevent overt bone disease (but not necessarily other conditions including osteoporosis) in the general population and expected to be considered safe if ingested over long periods of time.  The recommendations are not reliably adequate for high risk persons or persons with specific conditions. 

Concern is also voiced that many adult females may be ingesting calcium in higher than healthy amounts.

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