Not in winter if you live in northern latitudes: "If you live north of Atlanta (ahem, Boston), it’s impossible to produce vitamin D from the sun in the winter,

Not in winter if you live in northern latitudes: "If you live north of Atlanta (ahem, Boston), it’s impossible to produce vitamin D from the sun in the winter, because the sun ray’s never get high enough in the sky for the ultraviolet B rays (UVB) to penetrate the atmosphere. This can be a problem for most of us that aren’t lucky enough to have winter homes near the Equator." source: http://www.bostonmagazine.com/health/blog/2013/01/11/vitamin-d-sun-winter/ http://www.bostonmagazine.com/health/blog/2013/01/11/vitamin...