Calcium, k2, vit D and magnesium are a good combination. I take all of them now. Years ago I was always, permanently tired and thought I needed 12 hours sleep at least a night!! Since taking this combination I literally have troubles sleeping! I sleep just from 12.30 till 6.20 every night. Even when wanting to go to sleep I don't feel tired! I'm bright when I wake and not tired.
I take the combination of these as I had cancer and have bowel problems as well and magnesium citrate is meant to help both as is calcium. Then calcium should be balanced with vit D3 and k2. I also take the purest d3 in liquid form and the purest vit d as many have aspartame in.
I haven't got proof it's down to these as I also changed to having 3 small meals a day and pretty much plant based foods except a wee bit of chicken or fish.
Something has dramatically changed my sleep and I am sure it's this combination. (Could of course just be a placebo effect of wanting to feel better and thinking they are working-lol!!!)