In a recent article, John Cannell, MD — Executive Director of the nonprofit Vitamin D Council — explains how the organization arrived at its recommendation that all adults should take at least 5,000 IU/day of vitamin D for the rest of their lives [see blogpost here]. Previously, we had described research surrounding the potential benefits of oral vitamin D3 supplementation for various pain conditions; however, some may believe that 5,000 IU/day is too much, while it could actually be inadequate for many patients with chronic pain.
As Cannell acknowledges, the U.S. Institute of Medicine’s Food and Nutrition Board claims that merely 600 IU/day of vitamin D is enough for most adults, while the Endocrine Society says 2,000 IU/day is sufficient. However, he notes, “We think the safest thing to do while all the research is going on is to maintain natural vitamin D levels.”
By “natural,” Cannell is recommending vitamin D levels obtained by persons with daily sun exposure, such as lifeguards, some construction workers and gardeners, and others who regularly work outside, exposing significant areas of their skin to sunshine. “This is how our ancestors behaved throughout our evolutionary history,” Cannell observes.
Cannell references a relatively good study examining the vitamin D levels of people who get plenty of sun exposure, which was published by Luxwolda et al.  in the British Journal of Nutrition. The researchers discovered that healthy persons with traditional outdoor lifestyles, living around the African equator (the “cradle of mankind”), have average circulating vitamin D levels — ie, 25(OH)D — of 46 ng/mL (115 nmol/L).
Cannell remarks that most people do not have their blood tested regularly for vitamin D, so a recommended daily dose of supplemental vitamin D is needed that (a) is easy to obtain at pharmacies, (b) will get at least 97% of people above 30 ng/mL of 25(OH)D and most persons at 40-to-50 ng/mL, and (d) will not cause anyone to reach toxic levels. Besides those 4 goals, Cannell also takes into account body weight; since, apart from genetics, body weight is a significant determinant of vitamin D levels. The more a person weighs, the more vitamin D they need to take.
In support of this, Cannell describes a large study by Robert Heaney and colleagues that examined the relationship of body size and vitamin D status [see, Drincic et al. 2012]. These investigators found that, for a normal weight adult, 5,000 IU/day of total vitamin D input was needed to obtain a 25(OH)D level of 40 ng/mL. Cannell emphasizes that this pertains to an “average adult” and the final vitamin D level obtained by any dose also depends on baseline level, sun exposure, diet, and genetics.
More specifically, the researchers calculated from their data that a total input of 70-80 IU/day/kg-of-body-weight is needed to achieve 25(OH)D of 40 ng/mL. That works out to be about 35 IU/day/pound; so, a 100 pound woman would need 3,500 IU/day of total input, whereas a 300 pound man would need 10,500 IU/day. Note: this is total input from all sources, including sunlight, diet, and supplements.
Taking all of the above factors into account — and considering that most persons in modern society do not acquire much vitamin D from sunlight or diet — Cannell concludes that 5,000 IU/day of vitamin D supplementation is about right for the average adult.
In his brief article, Cannell does not address specific health or medical benefits to be gained by more optimal 25(OH)D levels; although, from an evidence-based perspective, his organization has explored the potential of vitamin D in a variety of preventative and therapeutic roles. Additionally, he does not state whether vitamin D3 or D2 is preferred, but in prior writings oral vitamin D3 supplements, taken daily, have been emphasized by Cannell (as well as by our own research on the subject).
In 2008, we published ground-breaking research review papers focusing extensively on the potential benefits of vitamin D supplementation in patients with various chronic pain conditions, particularly those musculoskeletal in nature. These papers have now been archived and are still accessible as follows:
Vitamin D – A Neglected 'Analgesic' for Chronic Musculoskeletal Pain:
An Evidence-Based Review & Clinical Practice Guidance
> Full Report [50-pages; PDF Here]
> Practitioner Briefing [7-pages; PDF Here]
PPM Journal Article: Vitamin D for Chronic Pain [13-pages; PDF Here]
Vitamin D: A Champion of Pain Relief — Patient Brochure [6-pages; PDF Here]
Since publication of those papers, a number of followup Pain-Topics UPDATES articles have examined and summarized the latest relevant research findings and commentary on the subject [click here for a listing of those articles]. Several points are worth repeating…..
- Vitamin D deficiencies have been associated with a variety of chronic pain conditions, such as back pain, osteoarthritis, fibromyalgia, inflammatory bowel disease, and others. In many cases, research has demonstrated the efficacy and safety of vitamin D3 supplementation in helping to alleviate pain and to improve functionality and quality of life.
- At the same time, much of the research has been of relatively poor quality and biased in one way or another. Larger-scale, randomized, controlled trials with higher vitamin D dosing and adequate followup times are still needed.
- Unfortunately, there are inconsistencies in the quality and quantity of vitamin D content in over-the-counter supplements, and higher oral dosages (eg, 1,000 IU D3 tablets) are not available in some countries. Daily oral dosing of vitamin D is more consistent with “natural” intake than once-weekly or less frequent megadoses administered orally or via injection.
- The optimal dose of vitamin D3 supplementation and subsequent 25(OH)D levels in persons with pain have not been determined. While the 5,000 IU/day and ≥40 ng/mL 25(OH)D recommended above by Cannell may be adequate for healthy persons, this could be suboptimal in most cases for helping to ameliorate painful conditions. Research to date has not fully explored effects of more adequate dosing, long-term in pain management.
- Blood tests for vitamin D — ie, 25(OH)D serum-level assay — can be costly and inconsistent from one laboratory to another, but this test is the only way to know if supplementation frequency and amount are adequate for individual patients.
- Aside from the other factors that may ultimately influence 25(OH)D levels, possible interactions with medications — eg, antacids, anticonvulsants, corticosteroids, and others — may reduce the potency of vitamin D. Malabsorption syndromes and bariatric procedures have been associated with vitamin D insufficiency, as have alcohol consumption and tobacco smoking.
- Most persons get adequate calcium from their diet and do not need extra calcium in conjunction with vitamin D supplementation, unless specifically indicated.
Clearly, there is still much to learn about the role of vitamin D supplementation as an adjunct in the management of chronic pain conditions, which can only be answered by high-quality research trials. Meanwhile, there is ample credible evidence for practitioners and patients to learn more and consider this relatively safe and inexpensive therapy.
> Drincic AT, Armas LA, Van Diest EE, Heaney RP. Volumetric dilution, rather than sequestration best explains the low vitamin D status of obesity. Obesity. 2012;20(7):1444-1448 [abstract here].
> Luxwolda MF, Kuipers RS, Kema IP, et al. Traditionally living populations in East Africa have a mean serum 25-hydroxyvitamin D concentration of 115 nmol/L. Br J Nutr. 2012;108(9):1557-1561 [abstract].