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Comment by MarkusWandel | Hacker News Reader

One thing I didn't see in this. Probiotics. So you have an active culture yoghurt, for example, that has one or a small number of bacterial species in it. This is claimed to benefit your gut biome. But how? Surely [re]introducing these few species hardly matters, given the overall diversity?

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Some studies show bacteria from fermented foods colonizing the colon and others do not, although regular consumption does tend to marginally increase microbiome diversity (a generic and in many ways crude measure of GI health). In theory, an optimally functioning GI tract would be killing a majority of the live bacteria long before they reach the colon via a combo of enzyme activity, stomach acid, bile, pancreatic enzymes, and immune activity on the way down. What has been more consistently shown is fermented foods causing decreases in GI inflammation and other positive impacts. Some researchers now believe that many if not most of the benefits come from all of the microbial action prior to consumption.

Fermenters such as Lactobacteria do a lot of work for us ahead of time, such as breaking down so-called 'anti-nutrients' and converting low-bioavailability nutrients into high bioavailability nutrients, producing anti-inflammatory metabolites, outcompeting pathogenic bacteria and fungi, and so forth. Bacterial fermentation has even been shown to break down pesticides [0], aflatoxins [1], and other potential contaminants present in the raw food. I wouldn't be shocked if microplastics and/or PFAS gets added to that list, at least under certain conditions, in the coming years.

[0] https://www.tandfonline.com/doi/abs/10.1080/10408398.2012.67...

[1] https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3737493/

> Some researchers now believe that many if not most of the benefits come from all of the microbial action prior to consumption.

That seems counter to the whole idea behind modern research on the importance of the gut microbiome and a throwback to the thinking of the previous century.

Certainly some of the work of bacteria is done before but that’s well known as many foods are fermented but the cultures are killed or pasteurized afterwards. Classic American yoghurt was like this, but there’s clear benefits to yoghurt with live cultures. Even if many bacteria don’t colonize the gut their presence in the food or taken separately appears important.

In my opinion the evidence is overwhelming that actual probiotic bacteria themselves are important, not just their by products in the food. Our immune system detects healthy bacteria both living and dead and lowers inflammation in response, etc. There’s a lot of research on the topic and good summary research (1, 2). The presence of the bacteria also change the gene regulation in the intestines.

Fecal transplants can directly treat diseases, or trigger diseases with maladaptive bacteria (3).

1: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC8512487/ 2: https://www.sciencedirect.com/science/article/pii/S277250222... 3: https://www.frontiersin.org/articles/10.3389/fimmu.2022.9917...

Yeah but fecal transplant bacteria isn't comprised of the sort of transient bacteria generally found in probiotic sources. It leads to a kind of hard-reset for gut flora. There are few sources that offer bacteria that will persist in the gut, I think I read kefir is one of them, but to what extent I'm not certain.

Even transient probiotics provide benefits too. Even when killed by stomach acid they trigger certain beneficial pathways. Many, perhaps most, traditional diets from around the world featured some live-culture fermented dish as a staple. Likely our bodies evolved to expect large daily exposure to certain healthy bacteria, and societies that ate live cultures with those bacteria would have better health.

Fungi will start feeding on plastic in the environment relatively soon. Digesting plastic in an animal digestive tract is a tougher nut to crack, similar in principle to digesting celulose.

Citation?

yeah I always found it a little counter intuitive how eating bacteria would be good for my gut insofar as most the GI tract is meant to be major gauntlet for bacteria.

But I get dodgy IBS-like issues eating spicy food but consuming fermented foods in proximity really helps settle the stomach. ie Kimchi affects me less than other spicy dishes while eating natto after having a lot of spice can really help. Ditto for yoghurt but I'm lactose intolerent and so many lactose-free yoghurts are full of crap

What crap is in lactose-free yoghurt? Afaik they add lactase which lactose tolerant ppl still “produce” after weaning. So the lactose is simply “pre-digested” into glucose and galactose.

most dairy free yoghurts (and lactose free yoghurts) are full of stabilisers and sugar

Could be any other reason.

BTW, you can make your own yoghurt, it’s very easy.

From what I read and researched online is that probiotics aren’t the bacteria you need, but are sort of good neighbors to the needed bacteria and create an environment they need to thrive by balancing pH of the gut and outcompete the “bad” bacteria and yeast.

The only thing I have to say about that is that pH is probably not very clinically relevant. The rest more or less checks out.

Yeasts are pretty sensitive to pH levels

To say nothing of viruses, which make up a huge (but not well understood) portion of our microbiome. Current estimates put the number at over 100,000 unique species and perhaps a few hundred trillion viruses residing in the human microbiome, far eclipsing endogenous and bacterial cells.

(heard from probiotics researcher)

Probiotics can potentially be highly effective, but you must eat some specific probiotic that helps you. The science of figuring out what type of probiotic you need is not very advanced.

Pharmasies sell probiotics for consumers and there are also foods that claim to have benefits, but they don't usually work, or work only by accident.

If you have been taking antibiotics, your biome is likely out of order. Fecal transplants can help.

Almost all food can be considered "probiotics", as pretty much everything is covered in microbes and provides food for microbes when eaten. A diet that promotes a healthy microbiome is going to be much more effective than supplementing lactobacilli or whatever.

>A diet that promotes a healthy microbiome is going to be much more effective than supplementing lactobacilli or whatever.

This may be generally true, but there may be situations where it is significantly better to do both, if we are talking about probiotic pills. Needs more research before making definitive statements (other than the reasonable stance that careful refinement of diet should always be the starting point when possible).

Fermented foods are on another level, though. It appears that increasing consumption of fermented foods is just plain good for us as a general rule. May someday be a standard corollary to "eat your veggies" for overall health and longevity.

That's why so many ancient cultures made beer. Basically every culture that began eating grains immediately also started fermenting them into beer.

It wasn't for the alcohol, that was normally very low in c. 5000BC beer anyways. It was because people that consumed it were healthier than those that didn't. Fermentation is nutritius and beneficial beyond alcohol/calories/potable water.

One anecdote. I had a friend with ongoing gut problems for years and tried giving him probiotics in pill form and it didn't really do anything. But recently he's discovered taking garlic juice seems to make things better. Presumably it kills of whatever bacteria that were upsetting his gut.

Two thoughts:

a) By introducing a large number of one or a couple of particular species, you're influencing the demographics.

b) The type of creatures you find in fermented foods are exactly the type of creatures who can help you digest those foods.

My 2 cents hypothesis : as some food “kills” many organism (garlic for exemple is an excellent gut cleaner), you also benefit to re-fill “good” organism like those in yoghurt.

Garlic is both antimicrobial and a rich source of food (oligosaccharides) for many strains of gut bacteria. It happens to be a favorite additive to fermentation recipes for this reason.

I think you’d have to eat a colossal amount of garlic for its anti-microbial properties to have any measurable impact on your gut bacteria.

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