In this issue of American Family Physician, Drs. Casey, Slawson, and Neal review recent recommendations on vitamin D supplementation.¹ The authors focus on guidelines from the American Academy of Pediatrics (AAP) that recommend increasing the minimum daily intake of vitamin D from 200 to 400 IU in all infants and children, including adolescents.² When considering these guidelines, it is important to be aware of the evidence behind them.

As mentioned in the article,¹ the AAP guidelines are based on consensus opinion and indirect evidence rather than prospective, patient-oriented evidence. Additionally, several organizations are currently establishing guidelines on vitamin D intake, which will likely reveal a continuum based on available evidence, as well as other factors, such as the population being evaluated. For example, the U.S. Preventive Services Task Force has not issued a recommendation on routine vitamin D supplementation, although the Canadian Paediatric Society recommends 800 IU of vitamin D per day for breastfed infants during the winter months.³

The AAP recommendations may have been motivated by several factors. The main influences, although not all-inclusive, can be broadly categorized as follows:

• Potential limitations of previous recommendations. A dosage of 200 IU of vitamin D per day may be inadequate to increase 25-hydroxyvitamin D levels to a sufficient level of more than 20 ng per mL (50 nmol per L) or to prevent rickets, whereas 400 IU per day appears to be an appropriate dosage to reach sufficient levels.^4,5

• Safety of increased dosing. A dosage of 400 IU of vitamin D per day does not appear likely to cause toxicity; oral administration at dosages several times higher than this level has been shown to be safe.⁶

• Simplification of recommendations. Previous recommendations for vitamin D supplementation took into account multiple factors, including age, skin pigmentation, geography, nutritional status, and the need to limit sun exposure.⁷ To simplify incorporation, the updated recommendations apply a single increased dose for all infants, children, and adolescents, thus reducing the number of variables for physicians to consider during a typical clinical interaction.

• Discovery of additional benefits. A number of trials, mostly observational, demonstrate the potential long-term benefit of vitamin D supplementation in early childhood in lowering the risk of conditions such as type 1 diabetes.⁸ These findings are based on evidence beyond that taken strictly from prospective trials. As the AAP guidelines suggest, recommendations may require a compromise between currently available prospective data for larger populations, available evidence for particularly vulnerable groups, and emerging evidence that may need to be considered cautiously.

When reviewing recommendations, it is reasonable to expect differing conclusions depending on the organizing body issuing the guidelines and the complex factors under consideration. In many ways, the development of recommendations parallels the balance physicians must make when counseling patients on vitamin D supplementation. Physicians must consider variables such as patient and family history, as well as regional and seasonal variations. The right dose of an intervention requires a careful understanding of the evidence, the circumstances and, most importantly, the patient.