All throughout human history until recently, if you killed an animal and harvested its organs and meat, or stumbled on a bounty of wild berries or other tree or bush fruit, or managed to squeeze some of the products of mammary glands from a ruminant like a goat, you would ferment the food to keep it from becoming inedible or poisonous. Surely the earliest humans, hungry and desperate at times, learned that many foods not consumed would ferment but remain edible.
Fermentation is essentially controlled rotting: the production of lactic acid by bacteria, the production of ethanol by fungi. You could, for instance, store milk or cream in the stomach of an animal you killed and used as a portable bag, and the rennet in the stomach lining would convert it to cheese. Or you would bury the excess meat and organs, fish, vegetables, eggs or other foods in the ground, allowing it to ferment and retrieved in a few weeks or months, especially when fresh food fell into short supply. Sauerkraut, fermented cabbage, was known to last for months and became one of the foods of choice to bring along on long ocean voyages to prevent scurvy. Such fermented foods persist to this day as garum (fermented fish), natto (fermented soybeans), of course, yogurt.
Then came refrigeration. Aside from the sporadic and relatively short-lived practices of saving ice from the winter (as long ago as 10,000 years ago in China) or shipping it from cold to warmer climates, large-scale refrigeration changed the way we ate. At first only available as a commercial process, by 1927 home refrigerators got their start, with a big boost when Frigidaire developed the refrigerant, freon. Then everything changed.
Refrigeration meant that foods like vegetables, meats, and fruits could be stored for extended periods and would not ferment or rot. In fact, as with so many modern habits, people started to view the products of fermentation with some distrust, as it seemed just a step away from being rotten (the exception being the products of fungal fermentation, beer and wine). Most people, upon viewing the cloudy, slimy bacterial soup that develops in veggies submerged in water, for instance, would promptly toss it in the trash, not recognizing it as edible and actually healthier. It means that our intake of Lactobacillus, Bifidobacteria, Leuconostoc and other bacterial species dropped way down to nearly nothing except from minimal surface contamination. And, even if you consumed common fermented foods like yogurt, most commercial preparations are fermented for the briefest period to hasten production or don’t even contain live cultures.
Combine our near century-long failure to consume fermented foods with practices like taking antibiotics, being exposed to herbicide and pesticide residues in commercial food, emulsifying agents in processed foods, and GMOs with glyphosate and Bt toxin, and we have a sure-fire way to create dysbiosis, massive disruption of bowel flora, and small intestinal bacterial overgrowth, SIBO.
My point: Return to the foods that humans consumed for millennia before refrigeration made us squeamish. It is part of your effort to regain health, in this case through restoration of a healthy oral and gastrointestinal microbiome.