Vitamin D supplementation

I was very impressed with Dr Schwalfenberg’s article on vitamin D in the May issue of Canadian Family Physician.1 Certainly vitamin D deficiency is common in northern regions, such as Canada, and its association with elevated risk of cancers, multiple sclerosis, osteoporosis, and other conditions is concerning. This is an important health issue about which our colleagues should be well informed, and the review contributes substantially to this end. The only point I’m concerned about is the implication that prescribing vitamin D2 (ergocalciferol) might be unsafe in managing deficiency. The papers referred to regarding vitamin D2 toxicity describe unusual cases of clear overdose, lack of monitoring, and ingestion of unregulated supplements. I have prescribed vitamin D2 dozens of times over the past few years and have found it to be effective in correcting vitamin D deficiency. Appropriately prescribed and monitored, vitamin D2 therapy doesn’t, in my experience, result in a follow-up blood level of 25-hydroxyvitamin D (25[OH]D) higher than desired. To correct a deficiency, I prescribe Ostoforte (1 capsule weekly for a few months, depending on the degree of deficiency). I check 25(OH)D levels after treatment (aiming for at least 80 nmol/L, but ideally 100 to 110 nmol/L), and then recommend an over-the-counter vitamin D3 supplement for maintenance and prevention (typically 1000 to 2000 IU per day). Once again, I commend you for an excellent review and for elevating awareness of this topic.

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