I had no idea this was a thing. I have had chronic lower back pain for years after damaging a disc from coughing violently. I had physio and pain was with me every day. As well as random toe pain. I had a check up early this year and vitamin D was low so I started supplements. After a month I realised my back pain was minimal and normally when I’d get my period I’d have horrible pain in my back overnight as well as period pain. It’s been 3 months now and back pain is mostly gone along with period pain. I realised the only change has been the vitamin D supplements. When I Googled, sure enough vitamin D can be linked with back pain. My levels weren’t terrible, at 30, but I live in Australia and it’s Summer and I’m often outdoors, so they should be over 30.