A few cups of green tea a day can protect your brain? But what about coffee?

Both tea and coffee are known for their neuroprotective compounds, and previous studies have linked tea and coffee consumption to cognitive benefits, but few studies have investigated their direct link to changes in brain structure in older adults.

Recently, a study led by the Graduate School of Medical Science at Kanazawa University in Japan reported that there was a significant link between drinking more green tea and less white matter damage in non-demented elderly people. The results showed that drinking 3 or more cups of green tea a day may help protect brain health, while drinking coffee has no significant effect.

The study, published in npj Food Science, is part of the Japan Prospective Study on Aging and Dementia Collaboration, a large-scale, multi-site observational study involving eight research centers in Japan.

Aging is a major risk factor for dementia and leads to brain changes such as brain atrophy, hippocampal shrinkage, and increased white matter lesions. White matter lesions often indicate small vessel disease and are associated with cognitive decline, vascular dementia, and Alzheimer's disease. The current study aimed to evaluate the effects of green tea and coffee consumption on white matter lesion volume, hippocampal volume, and total brain volume using magnetic resonance imaging data.

Study data collection was conducted between 2016 and 2018 and included dietary assessments, MRI scans, and cognitive assessments of 8,766 participants aged 65 years and older, and daily green tea and coffee intake was measured using a food frequency questionnaire divided into 4 levels: 0-200 ml, 201-400 ml, 401-600 ml, and ≥601 ml.

Brain MRI scans provided data on white matter lesion volume, hippocampal volume, and total brain volume. In addition, the researchers applied advanced statistical models to adjust for confounding factors, including demographics, health status, lifestyle habits, and genetic risk factors for Alzheimer's disease. The analysis excluded participants with mild cognitive impairment, dementia, or incomplete data, ultimately narrowing the cohort to 8,766 people. After adjusting for confounding factors, it was found that higher green tea intake was significantly associated with lower white matter lesion volume.

Participants who drank 600 ml of green tea per day had 3% lower white matter lesion volume than those who drank 200 ml or less per day, and those who drank 1,500 ml of green tea per day had 6% lower white matter lesion volume than the control group.

The results also showed no significant association between green tea intake and hippocampal or total brain volume. Coffee drinking did not significantly affect white matter lesion volume, hippocampal volume, or total brain volume. The study also investigated subgroups based on depression status and the presence of the ApoEε4 allele, the strongest risk predictor gene for Alzheimer's disease. The results showed that a significant reduction in white matter lesion volume with increasing green tea intake was only observed in individuals without depression or the ApoEε4 allele.

The findings suggest that the antioxidant and anti-inflammatory properties of green tea catechins, such as epigallocatechin gallate, may reduce vascular damage and promote brain health.

Compiled by: Gong Zixin