with the way research is going i'd expect to find it's something else in conjunction with D3 that causes that, and not merely D3. like D3 and a high sodium diet

with the way research is going i'd expect to find it's something else in conjunction with D3 that causes that, and not merely D3. like D3 and a high sodium diet, or D3 and <some local thing>. as mentioned though, i only think that 500-1000iu is not enough for most people. I'm not a doctor though, but it is one avenue of alleviating SAD as well as lethargy and stuff that most people vape/smoke/caffeinate to deal with.