I remember reading that the number one cancer ~100 years ago (e.g 1920's era) was stomach cancer.
The thinking was that everyone ate pickled or canned foods due to a lack of refrigeration. This in turn led to the stomach cancer.
I mention this in conversation when people talk about food being "better" back in the day.
It's also a reminder that "it's not the poison, it's the dose". Fermented/pickled foods are probably good for your gut biome up to some threshold but then can begin to have negative effects.
I have to check sources on this but to my recollection, the biggest reason for stomach cancer historically has been infection by Helicobacter pylori, which for decades caused duodenal/stomach ulcers in many adults with doctors only treating the symptoms instead of the underlying cause (the bacteria), because they simply didn't know how common it was as a cause of this problem. After Barry Marshall and Robin Warren showed in 1982 how it caused peptic ulcers, treatments for ulcers changed and gastric cancer rates fell from what I remember. Those two doctors even won a nobel prize for their discovery.
The thinking was that everyone ate pickled or canned foods due to a lack of refrigeration. This in turn led to the stomach cancer.
I mention this in conversation when people talk about food being "better" back in the day.
It's also a reminder that "it's not the poison, it's the dose". Fermented/pickled foods are probably good for your gut biome up to some threshold but then can begin to have negative effects.