I have been taking vit D for several years now after reading a number of articles as posted on the Globe and Mail website. Turns out the leading researcher in Canada for vit D takes 8000 iu's a day and I have been mimicking this now for some time. No colds, flu, elevated mood, lower cancer risk (cancerous tissue has been shown to be lacking in vit D)-studies involving millions shows the closer one is to the equator the less likely the chance for developing cancer no matter what one is exposed to. Being in Canada we need all the help we can get.