Pretty much if you live in a northern part of the northern hemisphere (above 49 degrees latitude) you need a vitamin D supplement.
I recall reading about a researcher in Boston (I think) who said after about mid October you could be sprawled buck naked on a rooftop all day and not get enough vitamin D from (brief winter) sun exposure.
I recall reading about a researcher in Boston (I think) who said after about mid October you could be sprawled buck naked on a rooftop all day and not get enough vitamin D from (brief winter) sun exposure.
http://www.cbc.ca/news/health/story/2008/05/16/f-health-vita...