Both Vitamin D and Magnesium have a calming effect. For me it's amazing how Vitamin D gives me that drained feeling you get when you're on the beach in the sun all day. Feels just like it. So I'm guessing if you go to high a dose on the D it can really wipe you out. Combine that with large amounts of absorb-able Magnesium and I think, yeah, anyone's going to feel pretty wiped out.