A stark disparity exists in vitamin D insufficiency prevalence across North America, with Canadian populations experiencing rates as high as 97% compared to 40% in the United States. This nearly threefold difference is primarily attributable to geographic latitude and the intensity of UVB radiation reaching northern regions. Individuals living at 40 degrees north latitude receive virtually zero vitamin D synthesis capacity during winter months, a critical limitation for populations in Canada and northern U.S. states. The epidemiological data underscores how seasonal and latitudinal variation in UVB radiation intensity directly drives population-level metabolic health outcomes. These findings highlight the urgent need for evidence-based vitamin D supplementation strategies and public health messaging tailored to geographic risk. Populations in higher latitudes may require year-round supplementation or dietary fortification to prevent widespread metabolic bone disease and neuromuscular complications. Read the full article on GMJ Newsroom.
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