Only Liquid Vitamin D. No way, over 63, this far north can I get/make enough Vitamin D without eating seals. Fine in the summer with shorts and t-shirts, but no way in the winter. Greens and other sources are fine, but orange flavored D drops are just too easy. Every other day is fine.
EDIT: Everyone should get their D levels checked, especially if over 50-60 or so. It's really is the only vitamin I have ever taken that I can feel. Mood, energy, general well being. If you have taken pills and nothing changes, try the liquid drops. For many, the pills just are excreted or not absorbed, but for whatever reason don't work, and won't raise D levels. A couple drops (depending on concentration/dosage) of some food (a bit oily food is best) in the AM is best (at night it can and will disturb sleep)