What’s so special about vitamin D?
Roles of vitamin D
Vitamin D deficiency versus insufficiency
It’s estimated that, depending on the season and latitude, exposure to the sun can provide 80%-90% of the required vitamin D. In the Northern Hemisphere, however, exposure to the sun is only maintained year-round south of the 35th parallel (a line that passes through northern Georgia and Alabama, then southern Nevada).
Because Quebec is located north of the 45th parallel, there’s not enough sunlight in the winter to allow the skin to produce sufficient amounts of vitamin D.
This means we have to rely on reserves accumulated in the liver during the summer months, on food intake and, if necessary, on supplements. This data must obviously be put in perspective with other factors, including age, skin type and pigmentation, clothing habits, time spent outdoors, etc.
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- Langlois K. et al., “Vitamin D status of Canadians as measured in the 2007 to 2009 Canadian Health Measures survey” https://citeseerx.ist.psu.edu/viewdoc/download?doi=10.1.1.620.8334&rep=rep1&type=pdf (source consulted November 10, 2020)
- Perry Wilson, F., “Vitamin D for COVID? We’ve Been Burned Before” https://www.medscape.com/viewarticle/939759?nlid=138015_5404&src=wnl_dne_201029_mscpedit&uac=268698PK&impID=2645348&faf=1#vp_1 (source consulted November 8, 2020)