Relatively fast onset gastro symptoms. Used to be fine with any beer but at about 21 started noticing the problem with a lot of largers. Asahi, Tsing Tao, seemed less of a issue. Not formula diagnosed.

Those are rice beers. You might have an issue with the grains used rather than yeast as there's no active yeast in the vast majority of beer.

And I suppose if someone really wanted to test out the beer-yeast theory, they could pasteurize the suspect beer and see if it causes the same issues.

You'd still get yeast peptides and glycans in there

All mass macro beer is pasteurized.

I don't know specifically about your symptoms, but one thing it could be is the carbonation.

All draught Guinness (including Guinness Draught cans) is not carbonated with just CO2, but with nitrogen and CO2 in a 70-30% (thereabouts) mix.

Additionally, when pouring a typically carbonated beer incorrectly (or not pouring it into a glass), a larger amount of CO2 remains in solution, leading to gastro bloat that can feel more uncomfortable than one would expect. You can experience bad pours even at bars, depending on who's behind the tap.

Lagers will have higher carbonation levels than most stouts, so that could be a factor.

I'm not your parent but similar issue. I doubt it's the CO2 if he's anything like me. I can drink coke all day long (well sugar free one anyway - but I don't drink pop except in rare cases)

Beer? Not much and it's worse the more days in a row I drink it. So 3 beers over 3 days total is worse than 3 beers one evening and then nothing.

And the alcohol doesn't matter. Same issue with alcohol free versions of the same beer. Hefeweizen like Erdinger which has lots of yeast on the bottom of the bottle is worse.

It's like the yeasty parts of the beer just take over my gut and wreak havoc.

I got things under control by both not drinking beer and switching to hard stuff if I'm after the alcohol part or just completely different drinks if I'm after the taste part as well as finding a probiotic that works for me.

Nota bene: for me I also got headaches with it all. Like really bad migraines and even with certain foods. The probiotics made it all go away as long as I don't overpower them with beer or Pizza for that matter. Ordered in Pizza, if I eat too much guarantees headache a day to two later.

Some yeast produce more msg than others? The way it accumulates for over time seems quite different than the gp that indicated fast onset. That sounds more like they have an active allergy. Perhaps to sulphites?

Interesting. I have what are basically eosinophilic esophagitis symptoms (feels like a food impaction) that seems to be acutely triggered by unfiltered wheat beers but I’m not bothered by rice beers. I had also homed in on yeast as a possible culprit.