I eat canned sardines (with skin and bones intact) either packed in water or extra virgin olive oil.  I've noticed they cause mild belching.  I've read that with respect to fish oil supplements, this reaction could mean rancidity.  Any thoughts as to whether this could be the same with canned sardines?  My husband thinks the bones are causing the issue because calcium can have this side-effect.  Thoughts?  It would be hard to give up my beloved sardines -- so tasty and economical.