Tea Consumption, Gut Microbiota Modulation, and Cognitive Health: An Integrated Review of the Microbiota-Gut-Brain Axis

Abstract

Abstract Tea (Camellia sinensis) is the second most widely consumed beverage in the world after water, and interest in its role in brain health has grown alongside the rising global burden of dementia and mild cognitive impairment (MCI). This narrative review synthesizes epidemiological, mechanistic, and gut-microbiome literature examining how habitual tea consumption may protect cognitive function, with particular attention to the microbiota-gut-brain axis as a candidate unifying pathway. Cohort studies and meta-analyses consistently associate regular tea intake with reduced risk of cognitive decline, MCI, and dementia, with evidence for a dose-response relationship 1-3. Mechanistically, tea catechins such as (−)-epigallocatechin-3-gallate (EGCG) exhibit measurable, if limited, blood-brain barrier permeability and exert direct antioxidant, iron-chelating, and anti-amyloidogenic actions 4-7, while the majority of ingested polyphenols reach the colon unabsorbed, where they reshape gut microbial communities, increase short-chain fatty acid (SCFA) production, and strengthen gut-barrier integrity 8-14. These microbial changes are proposed to reduce systemic and neuro-inflammation via vagal, endocrine, and immune signaling along the microbiota-gut-brain axis 15,16. Six figures summarize tea-processing chemistry, dose-response data, vascular and cognitive outcomes, direct neuroprotective mechanisms, gut-microbial taxa shifts, and a dual-pathway mechanistic model, alongside a summary table of key studies. We conclude that tea consumption is a promising, low-risk dietary strategy for supporting cognitive and gut health, while highlighting methodological limitations that must be addressed before firm clinical recommendations can be made.