This article gives a great overview of a fascinating field, and does so fairly responsibly, which is unusual in the popular press.
From the end:
'“Too many large-scale, spurious claims are being made,” Dinan said, mostly by people with something to sell. Although we have “very good data” from animal studies, he said, there’s nothing that could be described as solid clinical data linking the gut microbiome to depression or anxiety in people.'
This research is super exciting. It's also super new. The technology for sequencing gut bacteria on a large scale has only been around in a real sense for about 10 years, and only been affordable for about 3-5. We'll get there, and almost certainly gut flora matters massively for all sorts of biology, but it's important to temper excitable headlines.
> Although we have “very good data” from animal studies...
This is a pretty important thing to keep in mind. There are a lot of studies that I've seen, extending connections to humans from mice [1], even though understanding of the suitability of these mouse models has just recently (or hasn't) been studied [2].
So... "In humans, the data are more limited. Researchers have drawn links between gastrointestinal pathology and psychiatric neurological conditions such as anxiety, depression, autism, schizophrenia and neurodegenerative disorders — but they are just links." [3]
Absolutely. Humans aren't mice. That doesn't mean mouse studies aren't enormously helpful, but it does mean that we should take things with a grain of salt. The complexity of even a mouse is pretty enormous, and humans are that much more confusing.
As for gut to brain transmission, the first thing that comes to mind is being hangry but that's probably a different thing :)
For one, we have twice the number of bacterial species. But it seems more important to me that only 4% of the microbiome is shared between humans and mice.
That second argument does not imply that humans are more confusing than mice, just different.
My reaction was only against the apparently underlying assumption that humans, biologically, are more complex than mice, a remain of the idea that they are more evolved or a biased perspective due to the fact we study them in more detail.
From the end:
'“Too many large-scale, spurious claims are being made,” Dinan said, mostly by people with something to sell. Although we have “very good data” from animal studies, he said, there’s nothing that could be described as solid clinical data linking the gut microbiome to depression or anxiety in people.'
This research is super exciting. It's also super new. The technology for sequencing gut bacteria on a large scale has only been around in a real sense for about 10 years, and only been affordable for about 3-5. We'll get there, and almost certainly gut flora matters massively for all sorts of biology, but it's important to temper excitable headlines.