The easiest way to get the right amount of Vitamin D is by sunlight.
Sounds good except in the critical winter months when there is overcast for days at a time and cold when the sun is bright.
There other studies that show that Winter illness is directly related to lack of vitamin d. The study found that folks who take 2,000 units are unlikely to get flu and if there is lots of flu, 4,000 units/ day make flu unlikely at all. Further, pneumonia and other respiratory problems disappear.
To blow it off, is putting your self at risk during the winter