Coffee and Tea Drinkers Have Lower Risk of Stroke and Dementia

Are coffee and tea good for your brain?

Stroke accounts for 10% of all deaths worldwide and is one of the leading causes of disability. Dementia is “a progressive and unrelenting deterioration of mental capacity that inevitably compromises independent living.” Dementia can happen as a result of traumatic brain injury, brain tumors, poisons, brain infections, cerebral degeneration, and diseases of the vascular (circulatory) system like cerebrovascular diseases (e.g., stroke) and metabolic diseases (e.g., diabetes). Unfortunately, there aren’t a lot of effective treatments for dementia, so as you get older, prevention becomes more and more important.

You may be wondering what stroke and dementia have in common with each other, other than the fact that they both affect the brain. For one thing, having a stroke puts you at double the risk of developing dementia later on (called “poststroke dementia”). Also, a recent study showed that when you compare the risk factors and protective factors for stroke and dementia, there is a 60% overlap between the two. This means that most of the things that can affect your risk for stroke are the same things that can affect your risk for dementia.

Where do coffee and tea fit into these risks for stroke and dementia?

Coffee and tea are some of the most popular drinks. Several studies have shown that coffee and tea drinkers have reduced risks of stroke and dementia. A new study, recently published in the journal PLos medicine, aimed to dive deeper and find out more about this link.

When they ran the numbers, here’s what they found. Compared to people who did not drink coffee or tea, people who drank:

2-3 cups of coffee/day had lower risks of stroke, dementia, and poststroke dementia
3-5 cups of tea/day had lower risks of stroke and dementia
2-3 cups of coffee/day and 2-3 cups of tea/day (for a total intake of 4-6 cups/day) had lower risks of stroke, dementia, and poststroke dementia

Fun Fact: This study grouped decaf, regular, and instant coffee drinkers together into their “coffee drinkers” group. They also grouped black and green tea drinkers together into their “tea drinkers” group. This means that we can’t separate out the different varieties of coffee and tea from each other based on this particular study.

What is it about coffee and tea that can help them protect your brain?

Coffee and tea contain more than just caffeine.

Both coffee and tea consumption are linked with healthier lining of the blood vessels, which may protect against stroke. Coffee drinkers also tend to have lower risk for high blood pressure, heart disease, and type 2 diabetes. These can help to reduce risk of stroke and dementia.

Coffee and tea also contain several beneficial compounds that impact the brain (including caffeine) as well as being rich sources of antioxidants and other bioactive compounds that are thought to have anti-inflammatory and other protective effects.

Should you aim to drink 2-3 cups of coffee and/or tea each day?

What was interesting in this study was that one single cup of coffee and/or tea each day didn’t seem to be as protective as 2-3 cups per day was. If you’re already drinking coffee and/or tea regularly—and you want to continue—you can consider aiming for 2-3 cups per day. If you’re drinking more than that, you may consider cutting down a bit. This is especially true if you’re experiencing side effects of too much caffeine, like a fast heartbeat, irritability, nervousness, and difficulty sleeping.

While we know that coffee and tea contain much more than just caffeine (hello: antioxidants), we can use caffeine as a measure to know how much coffee or tea may be too much.

For reference, the recommended maximum intake of caffeine is 400 mg per day for good health. If you’re pregnant, trying to get pregnant, or breastfeeding, that maximum amount of caffeine reduces to 200 mg per day.

But, how much caffeine is in a cup of coffee or tea?

According to the Mayo Clinic, each 8 oz. (237 mL) cup of (non-decaf) coffee contains about 100 mg of caffeine, brewed black tea has about 50 mg, and a brewed green tea has about 30 mg. When it comes to decaffeinated coffee and tea, those numbers drop dramatically to about 2 mg of caffeine per cup.

Reference:

Zhang, Y., Yang, H., Li, S., Li, W. D., & Wang, Y. (2021). Consumption of coffee and tea and risk of developing stroke, dementia, and poststroke dementia: A cohort study in the UK Biobank. PLoS medicine, 18(11), e1003830. https://doi.org/10.1371/journal.pmed.1003830

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC8594796/

https://journals.plos.org/plosmedicine/article?id=10.1371/journal.pmed.1003830

Backgrounder articles:

About the study:

This study was done because of the increasing number of strokes and dementia, and to dig deeper into the controversy on the links between them and coffee and tea drinking (Do these drinks help or not?).
The researchers looked at 365,682 participants (50-74 years old) from the UK Biobank survey who reported their coffee and tea consumption. They found that people who drank 2-3 cups of coffee/day or 3-5 cups of tea/day (or a combo of 4-6 cups/day) had a lower risk for stroke and dementia. Coffee drinkers (with or without tea—but not people who drink tea without coffee) also had lower risks for poststroke dementia.
There were a lot of stats included, so I didn’t go into too much detail in the scoop, but here are the numbers for you (feel free to include them if your audience will want to see them):
- 2-3 cups of coffee/day reduces risk of stroke by 12%, reduces risk of dementia by 7%, and reduces risk of poststroke dementia by 20%
- 2-3 cups of tea/day reduces risk of stroke by 16%, reduces risk of dementia by 8%, and does not seem to reduce risk of poststroke dementia
- 2-3 cups of coffee/day and 2-3 cups of tea/day reduces risk of stroke by 32%, reduces risk of dementia by 28%, and reduces risk of poststroke dementia by 50%
The researchers split out different types of strokes (ischemic and haemorrhagic) and dementias (Alzheimer’s and vascular), but for simplicity, I didn’t go into that much detail in the scoop for your audience. Fellow nerds can feel free to check out figures 1 and 2 in the study for all the stats. ?
Conclusion: “We found that drinking coffee and tea separately or in combination were associated with lower risk of stroke and dementia. Intake of coffee alone or in combination with tea was associated with lower risk of poststroke dementia.”
Note that this study grouped decaf, regular, and instant coffee drinkers together into their “coffee drinkers” group, and they grouped black and green tea drinkers together into their “tea drinkers” group. This means that we can’t separate out the different varieties of coffee and tea from each other based on this particular study (more research is needed). Also, we can’t equate coffee/tea with caffeine, as what was measured was cups of coffee/tea, not amount of caffeine. We know that coffee and tea contain far more compounds than just caffeine (including many antioxidants).
All studies have limitations. This study was based on a survey of hundreds of thousands of people which is quite big, plus the participants were followed for an average of 11.4 years, which is long. These qualities make this a fairly strong study. However, it wasn’t a clinical trial that was randomized, blinded, placebo-controlled, etc. Therefore, it’s possible that people who took the survey were healthier than average, miscalculated or changed their coffee/tea intake over the years, etc. So, we can’t say that drinking coffee or tea prevents stroke or dementia, but we can say that people who drink 2-3 cups of coffee/day and/or 2-3 cups of tea/day have lower risks of getting certain types of strokes and dementias (correlation does not equal causation). Here’s a blog post I wrote on this concept: https://leesaklich.com/health-research/correlation-does-not-equal-causation/
Study strength is rated a 5/7 according to this chart (large prospective cohort study): https://www.compoundchem.com/2015/04/09/scientific-evidence/