Yes, I've recently become a vitamin D convert and have learned quite a bit about it through William Davis' Heart Scan Blog: <a href="http://heartscanblog.blogspot.com/" rel="nofollow">http://heartscanblog.blogspot.com/</a><p>It turns out that as you age, your ability to absorb vitamin D through sunlight decreases, so past 40, you probably need supplementation.<p>I simultaneously did two things starting Jan 1: I stopped eating wheat and started taking vitamin D. Although I can't pinpoint which of these is the determining factor, I can report that I have much more energy (no post lunch drag, nor desire to nap after work) as a result. I also seem to sleep better. Check out:<p><a href="http://heartscanblog.blogspot.com/2010/01/getting-vitamin-d-right.html" rel="nofollow">http://heartscanblog.blogspot.com/2010/01/getting-vitamin-d-...</a><p><a href="http://www.thevitamindcure.com/blog/" rel="nofollow">http://www.thevitamindcure.com/blog/</a>