'D' is for Dilemma: Two Vitamin Guidelines, Two Recommendations

Best Evidence Review

Charles P. Vega, MD


January 05, 2011

In This Article


These recommendations are built on evidence and take into account important variables, such as the differential synthesis of vitamin D across the population and the aging of the population as a whole. Although they advocate more aggressive supplementation with vitamin D than what is currently recommended, Osteoporosis Canada's guidelines seem reasonable.

It is therefore remarkable how these recommendations differ from those of the Institute of Medicine.[8] The Committee to Review Dietary Reference Intakes for Vitamin D and Calcium evaluated over 1000 studies and considered the full potential of vitamin D to improve health and decided that there was little to recommend supplementation with calcium and vitamin D other than maintenance of bone health. The evidence for vitamin D in the prevention of other health outcomes, such as falls and cancer, was considered mixed and inconclusive.

The Committee was not only less enthusiastic regarding the benefits of vitamin D, but they were also more sanguine about the potential epidemic of vitamin D deficiency in North America. Even among persons with minimal sun exposure, they recommend supplementation at a dose of 400 IU per day, with a dose as high as 800 IU reserved for persons 71 years and older.

However, the Committee also notes that the risk for harms in vitamin D supplementation do not increase until the dose surpasses 4000 IU per day. And this wide range of doses, from 400-4000 IU daily, allows physicians and patients to follow their own conclusions regarding the best dose of vitamin D supplementation. Some physicians will examine the evidence for themselves, conclude that vitamin D levels seem to be important determinants in a number of health outcomes, and recommend high-dose supplementation with vitamin D. Other physicians will agree that the evidence regarding the efficacy of vitamin D supplementation in preventing disease unrelated to bone health is mixed, and they may recommend less aggressive supplementation. There does not seem to be a single correct answer when it comes to vitamin D, but the broad safety index of these supplements allows room for physicians to follow more aggressive or conservative approaches to therapy.

Regardless of the treatment decision, it is important that physicians remain aware of vitamin D and its role in health and disease. Patients are monitoring the debates regarding vitamin D and are sure to have questions. It is up to all of us to provide reasonable, albeit possibly divergent, answers.

Clinical Pearls

  • Many adults, particularly those at the highest risk for fracture, have evidence of vitamin D deficiency.

  • Vitamin D supplements seem to be important in the maintenance of bone health, although doses of 400 IU or less may not be effective in preventing fracture.

  • The current guidelines from Osteoporosis Canada call for vitamin D supplementation with 400-1000 IU per day among low-risk adults. There is no need to monitor 25-OH-D levels in these patients.

  • The Osteoporosis Canada guidelines also recommend vitamin D supplementation at 800-2000 IU per day among moderate-risk individuals, with possibly higher doses for high-risk individuals.

  • The guidelines regarding vitamin D supplementation from Osteoporosis Canada contrast with those from the Institute of Medicine, which recommends a dose of 400 IU daily for most adults.


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