Vitamin D plays a critical role in bone metabolism and many cellular and immunological processes, and low vitamin D levels have been associated with several chronic and infectious diseases. Previous studies have reported that many otherwise healthy adults of European ancestry living in Canada have low vitamin D concentrations during the wintertime. However, individuals of non-European ancestry are at a higher risk of having low vitamin D levels. This thesis examined vitamin D status in a sample of young adults of diverse ancestry living in the Greater Toronto Area. In my research I found that: 1) vitamin D levels (measured as 25(OH)D concentrations) are low in Canadian young adults, particularly in those of non-European ancestry; 2) vitamin D intakes, which were estimated to be on average higher than current Health Canada recommendations of 200 International Units (IU) per day, were inadequate to maintain optimal vitamin D levels year-round; 3) vitamin D levels undergo large seasonal changes. Winter 25(OH)D concentrations are substantially lower than those observed during the fall; 4) vitamin D intake is an important year-round predictor of 25(OH)D concentrations, but skin pigmentation and sun exposure are also important predictors during the times when UVB is adequate for cutaneous synthesis; and 5) vitamin D binding protein (VDBP) polymorphisms are significant predictors of 25(OH)D concentrations, but their effects vary by ancestry and season, indicating gene-environment interaction effects. My research shows that higher vitamin D intakes are needed to offset the seasonal drop in vitamin D levels and to ensure adequate vitamin D levels year-round for those at higher risk of insufficiency.
| Identifer | oai:union.ndltd.org:TORONTO/oai:tspace.library.utoronto.ca:1807/29730 |
| Date | 30 August 2011 |
| Creators | Gozdzik, Agnes |
| Contributors | Parra, Esteban J. |
| Source Sets | University of Toronto |
| Language | en_ca |
| Detected Language | English |
| Type | Thesis |
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