> You don’t need gut bacteria at all if you’re only eating food humans can efficiently metabolize on their own. You don't know what you're talking about. See h

> You don’t need gut bacteria at all if you’re only eating food humans can efficiently metabolize on their own. You don't know what you're talking about. See https://link.springer.com/article/10.1007/s00726-017-2493-3 https://link.springer.com/article/10.1007/s00726-017-2493-3 as an example (one of many). Specifically: Research has indicated that the profile of the gut microbiota is the key determinant of the levels of tryptophan catabolites (TRYCATs) in the systemic circulation. Consequently, the profile of the gut microbiota is an indirect contributor to the degree to which serotonin is present in the brain. As serotonin is a fundamental neuro-transmitter at every signaling terminus of the gut–brain axis (O’Mahony et al. 2015), this is a consequential fact. Aberrances regarding TRYCATs are known to play a role in the onset and progression of depression, chronic fatigue syndrome, and somatoform disorder (Maes et al. 2007, 2011; Maes and Rief 2012), and aberrances in the levels of neurotoxic and immunomodulatory TRYCATs have been observed in several neurodegenerative and neuroimmune diseases (Morris et al. 2016). As evidence regarding the impact of the human gut microbiota on the health of the gastrointestinal tract continues to grow, the significant correlation between these factors is becoming indisputable (Klose et al. 2010). Moreover, it is becoming clear that a highly responsive and mutual connection exists between the resident species of the gut microbiota and the host, primarily insofar as the host metabolome status is regulated by the microbiota locally and systemically (Zhang et al. 2015). Disruptions to the human gut microbiota have widespread implications. For instance, they are associated with diseases external to the intestine, including the systemic immune system, the genital system, the central nervous system, and adipose tissues (Ciarlo et al. 2016)