This may or may not apply to those of you with headaches, but I'll just mention it anyway. On one of my Whole 30s, I decided to add fermented foods to help with gut issues. I normally get a migraine (same mechanism as a headache) one or twice a year. That month I got TWO within two weeks. So fermented foods can be a migraine/headache trigger for some, even though I believe most of the paleo fermented foods are compliant.