Discussion in 'Other Health News and Research' started by Kyla, Jul 2, 2016.
It's not clear to me how GABA-eating bacteria in the gut could affect the brain, since even if these bacteria lower GABA levels in the gut and in the blood, GABA does not normally cross the blood-brain barrier, so the brain would remain isolated from the lowered blood levels of GABA.
GABA is also active in the enteric nervous system, thus, it could follow a deficiency of GABA in the gut (due to bacteria metabolization or otherwise) could cause both GI issues and CNS effects and inflammatory disease due to involvement of the vagus nerve. Perhaps this lack of gabaergic signaling in the ENS could mean a lack of gabaergic signaling in the brain, because the brain neurons are wired in parallel with the ENS and something wrong on one end effects the other. Perhaps the same bacteria that metabolize GABA in the gut can enter the blood stream and enter the brain, where they also metabolize GABA.
It seems like these ideas could be an explanation for the fabeled somatic link between anxiety and GI issues, or even the more recent emphasis on GI issues leading to anxiety.
The vagus nerve detects inflammation in the gut (and in other organs) via receptors this nerve has for the inflammatory cytokines IL-1β and TNF-α. When the vagus detects inflammation in the gut, it signals this event to the brain, and in response, the brain the ramps up its own level of inflammation. In this way, inflammation in the gut can trigger inflammation in the brain.
Insofar as brain inflammation might be behind some neuropsychiatric symptoms such as depression or anxiety, gut inflammation may play a role in such mental symptoms.
If GABA in the gut could somehow reduce intestinal infection, inflammation or the levels of these cytokines in the intestines, then it might influence mood.
But most people who take high doses of GABA as a supplement find that it has very little effect on their mood and neuropsychiatric symptoms such as anxiety.
In my own case, I had severe anxiety that appeared after catching a suspected coxsackievirus B infection (and several other people who caught the same virus from me also developed very significant generalized anxiety disorder — details about this virus on my website).
I found that supplement (like prebiotics and probiotics) which reduce gut inflammation noticeably lowered my anxiety levels; and likewise, supplements like turmeric that reduced brain inflammation also decreased my anxiety levels. But I noticed no anxiolytic effects from GABA supplementation, even in oral doses of several grams.
Though now and then, you do hear accounts of oral GABA supplementation having strong anti-anxiety effects, such as @alice111's case (see here) of oral GABA supplementation making huge improvement to her severe anxiety.
So it's not clear what's going on in these cases where oral GABA does have an anxiolytic effect. If could be that in these cases, GABA is able to get into the brain due to a leaky blood-brain barrier. Indeed, it has been suggested that oral GABA can be used as a means to detect a leaky blood-brain barrier (see the GABA challenge test — though this test has not been scientifically validated).
I am not an expert, but I doubt if such gut bacteria could get into the brain without causing serious symptoms such as encephalitis. You do find chronic bacteria brain infections with Chlamydia pneumoniae (often in Alzheimer's patients), but that is a smoldering intracellular infection.
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