I saw Dr. Andrew Weil on Dr. Oz awhile back and he said that you must take your Vitamin D with a meal that has fat. It needs the fat to break it down. He specifically said do not take it with breakfast as there usually isn't enough fat in our breakfasts and recommended taking it with dinner.
My daughters and I all were tested and we are all quite deficient in D. We are supposed to be taking supplements and my dr. said not to take the calcium with D as that doesn't have enough of the D. She said take plain calcium and plain Vitamin D. As soon as my bottle of calcium with vitamin D added is empty I'm going to do as my dr says.
I sure hope it helps me with my energy levels and depression!