Two to three cups of coffee or three to five cups of tea were linked to reduced incidences of dementia, stroke, and post-stroke dementia, a new study on hundreds of thousands of UK Biobank participants concluded.
 
Alzheimer’s disease and vascular dementia (caused by reduced blood flow to regions of the brain) are the two main dementia subtypes, and strokes are estimated to cause ten percent of deaths globally. Coffee and tea consumption have long been studied for potential neuroprotective properties, but to date, the causality behind the protective factor remains undetermined. However, researchers have pointed to the antioxidant, caffeine, and bioactives content in coffee, as well as the caffeine, polyphenol, and flavonoid content in tea. Each beverage also contains overlapping components, such as epigallocatechin gallate and chlorogenic acid.
 
In the present study, a team of researchers from Tianjin Medical University sought to expand upon the relationship between the two types of beverages, which are rich in flavonoids, and health outcomes in a large pool of healthy participants. While each of the beverages has been studied alone substantially, few studies have accounted for the consumption of both and how this might effect a variety of health outcomes.
 
In total, 365,682 participants who were recruited between 2006 and 2010 were tracked by the researchers until 2020, and, at the outset of the study, participants self-reported their coffee and tea intake. Hazard factors such as age, BMI, and history of a variety of disorders were accounted for. Throughout the study period, 5,079 participants developed dementia, while 10,053 experienced at least one stroke.
 
The lowest incidence factors for stroke and dementia were seen in participants who consumed two to three cups of coffee, three to five cups of tea, or four to six cups of both coffee and tea combined; these groups experienced a 32% lower risk of stroke and a 28% lower risk of dementia. Coffee alone or in combination with tea was also associated with a lower risk of post-stroke dementia.
 
There were some noted limitations in the study, such as that coffee and tea consumption was self-reported at baseline and may not reflect long-term consumption patterns. Additionally, there were relatively low rates of both stroke and dementia, and no causality could be determined because the study was observational in nature.
 
However, the findings nonetheless highlight a potential beneficial relationship between coffee and tea consumption and the risk of prevalent cognitive health conditions. “One potential mechanism may be related to the combined protective role of the different antioxidant and other biological contents in these two beverages,” the authors of the study concluded. “Second, coffee and tea have a specific polyphenolic content, characterized by hydroxycinnamic acids in the former, and catechins in the latter, which have demonstrated potential benefits in ameliorating endothelial function, insulin resistance, and anti-inflammation, and have different target molecules […] Third, both coffee and tea were related to lower cardiometabolic risks, including type 2 diabetes, hypertension, and CAD […] Fourth, the interaction between coffee and tea drinking for both stroke and dementia may have arisen due to chance. Finally, consumption of coffee and tea may jointly modulate certain cytokine activation.”