Tim Spector’s mother no longer recognizes him, and that personal loss became the catalyst for his radical rethinking of brain health.
The world-renowned microbiologist and co-founder of ZOE has spent over 15 years studying the gut, and now argues that many conditions we attribute to the brain — including depression, anxiety, and dementia — may actually originate in the digestive system. In a recent interview on ‘Diario de un CEO’, Spector cited studies showing that regular flossing could reduce dementia risk by nearly half, a claim rooted in the emerging science of the gut-brain axis.
This idea is not new, but it is gaining urgency. As early as the 20th century, Columbia University’s Professor Gershon demonstrated that the digestive tract contains a vast neural network — what he termed the “second brain” — capable of operating independently of the skull-bound organ. More recently, Mario Alonso Puig, a Harvard-trained surgeon and fellow, expanded on this in his book *El camino al despertar*, arguing that metabolic imbalances in the gut directly influence mental health, and that nutritional changes can profoundly alleviate anxiety and depression.
Supporting this, researchers at Stanford Medicine and the Arc Institute found that in ageing mice, shifts in intestinal bacteria trigger immune responses that disrupt vagus nerve signaling to the hippocampus — the brain’s memory center. When they stimulated this nerve in older mice, memory performance improved to youthful levels, suggesting cognitive decline is not purely neurological but can be modulated by gut health.
Further reinforcing the connection, a 2026 University of Cambridge study identified a specific bacterial group, CAG-170, that appears far more frequently in healthy individuals and is diminished in those with chronic illness — offering a potential biomarker for a “healthy gut.”
Together, these findings challenge the long-held assumption that brain ageing and mental illness are isolated neurological phenomena. Instead, they position the gut as an active regulator of cognition and mood, with implications for prevention strategies ranging from oral hygiene to dietary intervention and vagus nerve stimulation.
The human dimension remains central. Spector’s personal journey — from studying twins to questioning the foundations of ageing after his mother’s dementia — underscores how deeply this science resonates beyond data. It is not merely about mechanisms; it is about redefining what it means to age well in an era of longer lives but not necessarily better ones.
How does gut health affect mood and mental health?
Research shows the gut contains a complex neural network — the “second brain” — that communicates with the cranial brain via the vagus nerve. Imbalances in intestinal bacteria can trigger inflammation that disrupts this signaling, contributing to conditions like anxiety and depression, while improvements in gut flora through diet or probiotics may help restore balance.
Why might flossing reduce dementia risk?
Poor oral hygiene can lead to gum disease and systemic inflammation, which may negatively affect the gut microbiome. Since gut health influences brain function through immune and neural pathways, reducing oral inflammation via flossing could help protect cognitive function, with studies suggesting a potential reduction in dementia risk of almost 50%.