The most essential supplement

[Bruunhilde]

Someone posted that recently they heard if there was one single thing you supplemented, it should be X.

I can't remember who said it, or what it was! Help, anyone? I wanted to add this essential item to my repetoire of supplements. It's something I've never heard of and it's not one of the supplements used for AL recovery.

Thanks in advance if anyone knows what I'm talking about!