Re: A Predictive Equation to Guide Vitamin D Replacement Dose in Patients

To the Editor: Singh and Bonham's¹ study concluded that a majority of patients require higher vitamin D treatment and maintenance doses than are currently recommended. Their statement regarding the need for higher vitamin D doses and serum concentrations is important, especially considering the morbidity and mortality that adequate vitamin D intake can prevent. Their statement claiming that sunscreen prevents the absorption of vitamin D from ultraviolet radiation, however, contradicts previously published studies.

Multiple studies found that typical sunscreen use does not limit the absorption of vitamin D to a clinically significant extent. Farrerons et al² found that although vitamin D concentrations were lower in users of sun protection factor 15 versus placebo, concentrations were still sufficient to prevent a decrease in bone density or result in secondary hyperparathyroidism. Young³ found that adequate vitamin D concentrations were still obtained with appropriate sunscreen application despite higher vitamin D concentrations in nonsunscreen users. In addition, although sunscreen users' vitamin D concentrations did not increase during the study by Marks et al,⁴ they did remain within the therapeutic range and did not decrease.⁴

Pharmacists and physicians should be aware that vitamin D supplementation beyond 800 IU is often necessary. Despite sunscreen use, patients can absorb vitamin D; therefore, supplementation and lifestyle modifications may work together to increase, or at least maintain, therapeutic concentrations of vitamin D. It is essential that pharmacists and physicians counsel patients on lifestyle opportunities, either in place of or in addition to supplementation with medication for patients who prefer nonmedication regimens, and for patients who need an additional boost in their vitamin D concentration despite recommended supplementation.