If you live in a place where sunlight is scarce for months at a time in the winter, and you have no other guaranteed source, Vit. D deficiency is worth consider

If you live in a place where sunlight is scarce for months at a time in the winter, and you have no other guaranteed source, Vit. D deficiency is worth considering. I tried 400IU's a day in winter for a couple of years along with coffee. I noticed it enhanced the coffee buzz with a pleasant glow. The rest of the year I'll take my chances with sunlight.