Hello Anne,
I agree with you and I also started making my own kefir after I was diagnosed with IBS, I developped IBS after withdrawal from AD, but that might have been a coincidence.
Gut produces 95% of serotonine so our mood is definitely linked to our gut health.
Another good book to recommend is 'Gut' by Giulia Enders.
I would just like to add that acid reflux does not always have to be linked to high acid, it can be also low. I suffered badly, adjusted my diet what did not help much and the only thing the GP prescribed was Omeprazole, they did not wish to do more checks. I read somewhere online about sodium bicarbonate test for checking whether the stomach acid is low. I did the test and it seemed that mine was actually very low. I started drinking some cider vinegar with water before a meal and chewing my food properly, not drinking during the meal. In addition to this I read that the sphincter that connects stomach with oesophagus might not be closing properly due to diaphragm being weak, therefore acid is released towards the throat. I am doing twice daily breathing exercise to strengthen diaphragm. I feel much better now.