Vitamin D study


   Vitamin D, the "sunshine vitamin", plays a critical role in bone metabolism and many cellular and immunological processes (Click here to watch a video from Barbara Brehovsky, a graduate of our Biomedical Communications M.Sc. program, summarizing the important endocrine and autocrine roles of vitamin D). Recent studies in Canada have indicated that the prevalence of vitamin D insufficiency in healthy adults is surprisingly high, particularly during the winter months. In collaboration with investigators from the University of Toronto (Dr. Reinhold Vieth and Dr. David Cole) and the University of Saskatchewan (Dr. Susan Whiting), we have evaluated the seasonal variation of vitamin D levels in healthy young adults of diverse ancestry living in the Greater Toronto Area. This study, which was the Ph.D. research project of my student Agnes Gozdzik, explored the role of relevant factors (skin pigmentation, vitamin D intake, sun exposure) in vitamin D concentrations. Many of the participants in our study had suboptimal vitamin D concentrations (i.e. serum 25(OH)D concentrations lower than 50 nmol/l): 50% in the fall and 75% in the winter. We found that there were differences in vitamin D status between population groups, and also strong seasonal variation in vitamin D levels, with winter concentrations substantially lower than fall concentrations. For more details about this study, please see the paper published in the Journal of Nutrition (Gozdzik et al. 2010. J. Nutr. 140:2213-2220). The results of our study strongly support the vitamin D recommendations of the Canadian Cancer Society, which take into account known factors affecting vitamin D levels, such as season, skin pigmentation and UV exposure. Specifically, the Canadian Cancer Society recommends that adults living in Canada should consider taking 1,000 IU/day of vitamin D supplementation during the fall and the winter, and adults at higher risk of having lower vitamin D levels (people who are older, those with dark skin, those who don’t go outside very often, and/or people who wear clothing that covers most of their skin) should consider taking 1,000 IU/day all year around (http://www.cancer.ca/Canada-wide/Prevention/Vitamin%20D.aspx?sc_lang=EN)


Serum 25(OH)D concentrations during the fall and the winter in young adults of diverse ancestry (East Asians, Europeans and South Asians) living in Canada