From what I have read on these forums, the effects of probiotics in ME/CFS patients can change over time. Some people report that at once stage probiotics were helpful for their ME/CFS, but then 5 or 10 years later, they find they cannot take probiotics at all, because it worsens their ME/CFS.
So the effects of probiotics on ME/CFS seem quite variable over time.
The old formulation of AOR Probiotic-3 from 2013 you can see
here, and the current formulation
here. I've coped the ingredients below. As you can see, the main changes are the replacement of Enterococcus faecium with Streptococcus faecalis, and the replacement of Bacillus subtilis with Bacillus mesentericus.
But the Clostridium butyricum in the AOR Probiotic-3 remains the same, except that there is a little less of it in the new formulation.
So maybe that made a difference to the effects you experienced.
A cunning plan! I had the same thought myself about eating lots of butter for the butyrate.
This study found that butyrate from Clostridium butyricum down-regulated the expression of TLR4 in the colon. TLR4 is the same receptor that low-dose naltrexone blocks, so the benefits of Clostridium butyricum for ME/CFS may come from the same TLR4 mechanism.
Butyrate is absorbed in the small intestine though,
1 so will not reach the colon in high concentration. Whereas Clostridium butyricum lives in the colon, so delivers the butyrate into the colon. Maybe that makes a difference.
Interestingly enough, two other supplements that down-regulate TLR4 are oxymatrine and hyaluronic acid. We know that oxymatrine is often effective for ME/CFS; but hyaluronic acid is broken down by the stomach acid, and so not much enters the circulation, thus oral hyaluronic acid may not help.
I did at one point try transdermal hyaluronic acid, but did not notice much. However, I am a non-responder to Clostridium butyricum, oxymatrine and LDN, so I am not the best person to try hyaluronic acid.