For intestinal distress,
I have used iodine, nattokinase, digestive enzymes with extra pancreatic enzymes, ox bile, and L-Glutamine. Slippery elm and boiled okra have helped some too.
Also avoiding foods and other substances which I have found out cause me trouble.
Some of the things I avoid:
anything processed, additives, preservatives, etc.
grains, legumes (except green beans)
salicylates
anything that promotes growth of bacteria or fungi (the usual things: sweets and starches, dried fruit, nuts/nut butters, cheese)
nut and seed oils (due to Omega-6 and inflammation)
I use the FailSafe Diet from the Prince Albert Hospital Allergy Unit (in Australia) as a basis for eliminating the chemicals which naturally occur in foods, which might be problematic.
I don't eat food that other people make or cook.
I cook meat on low heat and not for too long.
----
Being careful about meal timing and amounts, being strict about food sources, and taking the supplements has helped a lot.
Being careful about washing dishes and cookware very thoroughly to rule out possible contamination.
Not eating food which is too old, or which might have been left too long in the temperature range of 45 - 150 degrees (Fahrenheit), which promotes growth of pathogens.
I have to stay careful or the intestinal distress returns.
For some time, I have to just eat beef, plain beef gelatin, and could add milk made more digestible with rennet tablets (Junket), and then added some yoghurt. Homemade yoghurt does better than store-bought. Then added green beans. Later okra.