[hollerith]

>Food is eaten in our stomachs by bacteria. If the bacteria in our stomachs can’t (or won’t) eat something, that means it’s not digestible.

Both of these are false. Bacteria are not needed for the proper function of the human stomach (or the small intestine). The human body produces digestive enzymes, HCl and bile (and maybe bicarbonate) which combined will digest most foods without any help from bacteria.

Bacteria are needed in the large intestine to convert fiber into short-chain fatty acids (SCFAs), but a person can live for many years without any of these SCFAs' being produced in the large intestine, although the person probably would be less healthy.

[josephg]

There’s more and more content these days talking about “the new science of gut bacteria” and talking about how important it is to our health and wellbeing.

Do you think all that is bunk / pseudoscience?

[hollerith]

Gut bacteria in the large intestine are generally considered (including by me) important for human health although again you would not starve to death or die of malnutrition if they all went away because the vast majority of the calories a person in the developed world gets are from foods that bacteria is not needed at all to digest and make use of those calories. Our ancestors 1000s of years ago however probably went through lean periods in which most of their nutrition came from very fibrous plant material with very little starches and free sugars in them, and in that situation, the calories from the SCFAs produced by gut bacteria might have often made the difference between survival and starving to death.