Low levels of certain bacteria in the Firmicutes phylum, including Blautia and Faecalibacterium, have been linked to the accumulation of trunk-fat specifically.23
Your Gut-Brain Axis Is an Information Highway
Gut microbes' effects don't only apply to your gastrointestinal tract. They interact with your central nervous system via the microbiota-gut-brain axis, a two-way information highway that involves neural, immune, endocrine and metabolic pathways.
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By promoting proinflammatory cytokines, bacteria may also play a role in damaging the integrity of the microbiota-gut-brain axis and the blood-brain barrier.25
There are also 10 gut microbiota genera with a significant link to Alzheimer's. Six are negatively associated with Alzheimer's, meaning they're less common in people with Alzheimer's than in those without the disease and may therefore have a protective effect.
The remaining four are positively associated with Alzheimer's, meaning they're more abundant in those with Alzheimer's disease, making them a risk factor for the condition. Specifically:26
Bacteria protective against Alzheimer's include Firmicutes phylum (Eubacterium nodatum group, Eisenbergiella and Eubacterium fissicatena group) as well as from
Actinobacteria (Adlercreutzia, Gordonibacter) and Bacteroidetes (Prevotella 9)
Bacteria associated with Alzheimer's include Firmicutes (Lachnospira and Veillonella), Actinobacteria (Collinsella) and Bacteroidetes (Bacteroides)