Drinking coffee and tea linked to lower risk of dementia, strokes - study

Drinking coffee and tea linked to lower risk of dementia, strokes - Tianjin Medical University study.
Moderate coffee drinking is apparently very healthy - but excessive caffeine is definitely not. Photo credit: Getty Images

Drinking coffee or tea appears to linked with a lower risk of stroke and dementia, according to a study that's being called the largest of its kind.

The researchers found healthy individuals between the ages of 50 and 74 who drank two to three cups of coffee or three to five cups of tea per day - or a combination of four to six cups of both per day - had the lowest incidence of stroke and dementia among 365,682 study participants.

Those who drank two to three cups of coffee and two to three cups of tea daily had a 32 percent lower risk of stroke and a 28 percent lower risk of dementia compared to people who drank no tea or coffee.

The study was conducted by Yuan Zhang and colleagues from Tianjin Medical University in China. The 365,682 participants studied were recruited between 2006 and 2010 and followed until 2020.

They self-reported their coffee and tea intake at the start of the study and over its period, 5079 developed dementia while 10,053 experienced at least one stroke.

"Our findings suggested that moderate consumption of coffee and tea separately or in combination were associated with lower risk of stroke and dementia," the study's authors wrote in the journal PLOS Medicine.

However, all participants were from the UK Biobank. The researchers noted that group reflects a relatively healthy sample relative to the general population, which could impact on the ability to generalise the study's findings. 

Also, the study findings are bad news for people who really, really like coffee - for example if you're an eight cups per day caffeine addict.

"What generally happened is that the risk of stroke or dementia was lower in people who drank reasonably small amounts of coffee or tea compared to those who drank none at all, but that after a certain level of consumption, the risk started to increase again until it became higher than the risk to people who drank none," said Professor Kevin McConway via The Guardian.

"Once the coffee consumption got up to seven or eight cups a day, the stroke risk was greater than for people who drank no coffee, and quite a lot higher than for those who drank two or three cups a day."

The Tianjin Medical University study is far from the first to associate health benefits with drinking tea and coffee.

Michelle Rauch, a registered dietician in the US, told Healthline that coffee has been associated with a reduced risk of some cancers, cardiovascular disease, type 2 diabetes, Parkinson's disease and cirrhosis.

She also highlighted the health risks of drinking too much tea and coffee, however.

"Tea and coffee contain compounds called tannins, which can interfere with iron absorption if taken in excess. These tannins can also cause staining to teeth when they build up on the enamel," Rauch told Healthline.

"Like coffee, the caffeine in tea can also cause an issue if taken in excess leading to restlessness, shakiness, rapid heart rate, insomnia and anxiety. The catechins in tea may interfere with some heart and blood pressure medications. 

"The health benefits from tea and coffee may be negated if sugar, honey, cream and other caloric or fat laden ingredients are added."