Eli5: If people have different types of gut bacteria what is the point of probiotics?
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Attempting to seed your gut with good bacteria makes sense after you’ve been on antibiotics
Antibiotics is a bit like like dropping a nuke on a city and hoping more”good” people survive than “bad” people. Probiotics helps boost the part of the population which you consider the”good” people.
The concept is that not all gut bacteria is as good. Some bacteria works very well in your gut while others will make you bloated, hurt and fart a lot. Probiotics is bacteria which generally works well in your gut. The theory is that by eating these bacteria they will take over from the bad bacteria making your digestion better. In reality though probiotics does nothing in healthy humans, even with gut flora issues. There is just too little bacteria making its way through the upper digestion system and the few that gets to your lower intestines gets out-competed by the existing bacteria. It may have some impact in people with reduced gut flora, for example people on general antibiotics. However this is also not proven.
Probiotics (the ones that make sense*) are very specific species of bacteria or yeast that are proven to be beneficial for you. The population of your gut depends on 3 things: what you’ve been exposed to, what you’re feeding it, and what works well together. Probiotics can aid with the first and the third one, introducing some beneficial folk that will boost the general positive population. Makes 0 sense if you don’t feed it though, or if it’s not the proven, registered strain that is produced in pills surviving the stomach acid. Regarding what to feed them: some probiotics are enhanced with prebiotics – kind of a starter meal for them, the rest relies on your diet. Good bacteria generally team up and fight the bad ones, usually not to kill off completely but to keep them in check (barely anything in nature is so black and white that it’s good or bad, what matters is the proportion). You are constantly bombarded by harmful microorganisms that will make you ill, and your gut is your second (after stomach acid) line of defence against the ingestible ones. In addition to that, how well you will process your food, absorb nutrients, and turn the food into beneficial and not harmful compounds (see: https://nutritionfacts.org/video/how-to-develop-a-healthy-gut-ecosystem/) depends on it. So you want to keep the population nice and healthy.
To conclude: people have different bacteria in the first place because of exposure differences, antibiotics usage, and their diets. Two people exposed to the same bacteria and having the same diet will have very minor differences in their gut flora. Imagine a garden in a non-sealed jar that you have to take care of for a pretty accurate analogy. With probiotics we can make sure everyone has been exposed (or re-exposed) to the bacteria & yeast strains we know for sure we all want to have.
*Most of them do not and are ineffective or even harmful – the market of dietary supplements is unregulated, if you want a good product pick one with registered medication status. For more info see: https://www.worldgastroenterology.org/UserFiles/file/guidelines/probiotics-and-prebiotics-english-2017.pdf
The efficacy of probiotics was disproven back in the 50’s. They don’t work, they’ve never worked.
Specifically for probiotics supplements: To generate profit.
Any time a company wants to claim that their product has a specific medical effect, they have to go through a stringent testing and safety screening process known as FDA Premarket Authorization (commonly known as FDA Approval). This is required by law.
No probiotics has any sort of FDA approval. This means that they can only be marketed as a supplement (an extra amount of a thing, bacteria in this case), and can’t make any specific claim of efficacy.
The variation in gut bacteria between individuals is similar to the variation in chicken noodle soup recipes between individuals. No matter how unique your recipe might be, you still need to start with chicken broth.
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