Writing in the journal npj Science in Food, a team of Japanese researchers investigated the associations between green tea or coffee intake with various measures associated with structural integrity of the brain among over 8,000 community-dwelling adults.
“Given that cerebral white matter lesions are closely related to vascular dementia and AD, our findings indicate that drinking green tea, especially three or more glasses per day, may help prevent dementia,” they reported. “Nevertheless, further prospective longitudinal studies and basic research are needed to validate our results.”
Green tea and cognitive decline
As background to their investigation, the researchers referenced previous epidemiological studies associating green tea consumption with slowing cognitive decline and noted that white matter lesions, indicative of cerebral small vessel disease, are associated with vascular dementia and Alzheimer’s disease (AD).
“Recently, a longitudinal study also identified white matter lesions as an independent risk factor for cognitive decline, even after accounting for traditional AD risk factors and MRI biomarkers, such as ApoE ε4 carrier status, total brain volume and HV,” they wrote.
With hypertension considered the most important risk factor for white matter lesions, the study also highlighted recent meta-analyses supporting the systolic and diastolic blood pressure lowering effects of regular green tea consumption
Green tea contains catechins, studied for their antioxidant and anti-inflammatory properties, anti-platelet aggregation and nitric oxide regulation in the vascular endothelium, as well as theanine with its reported antihypertensive effect. Another compound, epigallocatechin gallate, has been shown to confer neuroprotective effects by inhibiting amyloid β aggregation and production.
Study details
The current study analyzed data from a total of 8,766 adults aged 65 and older drawn from the Japan Prospective Studies Collaboration for Aging and Dementia between 2016 and 2018.
A food frequency questionnaire was used to assess green tea and coffee consumption, and brain magnetic resonance imaging assessed cerebral white matter lesions, hippocampal volume and total brain volume.
“This cross-sectional study found a significant association between lower cerebral white matter lesions and higher green tea consumption, but not coffee consumption, in older adults without dementia, even after adjusting for confounding factors,” the researchers reported. “Similar significant associations were observed when analyses were limited to older adults with normal cognitive function, excluding individuals with mild cognitive impairment.”
There were no significant differences between green tea consumption and hippocampal or total brain volume, and beneficial associations were not observed in people diagnosed with depression or with the ApoE ε4 gene variant.
“We can infer that, since depression and ApoE ε4 are strong risk factors for dementia, green tea may not be effective in reducing white matter lesions in individuals with depression and ApoE ε4,” the researchers suggested. They added that the sample size in these groups might also have been too small and that the prevalence of hypertension and diabetes was significantly higher in participants with depression.
As a limitation, the study noted that it only considered green tea and coffee consumed as beverage and not as snack, possible variations in green tea bioactive content due to brewing technique and the difficulty in determining causal relationships due to the cross-sectional nature of the research.
“Because our study was performed with older Japanese participants, it is necessary to clarify the association between green tea intake and cerebral white matter lesions in people with different ethnicities, genetics and lifestyles,” the researchers noted.
Source: npj Science of Food, doi: 10.1038/s41538-024-00364-w, “Green tea consumption and cerebral white matter lesions in community-dwelling older adults without dementia”, Authors: Shutaro Shibata et al.
