A recent thread on the “r/unpopular opinion” forum on Reddit has me thinking a lot about my relationship with coffee.
“Coffee culture sucks,” u/MyrtleGlenFarm writes. He elaborates with some colorful language.
I hate, hate, hate coffee culture. I can’t stand people saying, ‘Oh, I can’t do anything until I get a warm cup of coffee in me.’ Shut up. Being a former smoker, I recognize the addiction and subsequent irritability of coffee drinkers and it bugs me to no end that caffeine gets glossed over as an addictive substance… [Those people] need an intervention, not a nod of approval. Seriously, all you coffee drinkers are the biggest group of fucking enablers I’ve ever seen.
Coffee is big business. The average American spends $1,100 a year on coffee, and the average coffee drinker consumes about three cups a day. Americans under 40 increased coffee consumption 40% since 2015 alone. u/MyrtleGlenFarm has a point: coffee is everywhere, and it’s not going away any time soon.
But is coffee healthy? And do coffee drinkers live longer than non-coffee drinkers?
At the turn of the 20th century, it was considered common knowledge that coffee was unhealthy—there were advertising claims that coffee drinking caused blindness and that “you can recover from any ordinary disease by discontinuing coffee.” And while that may obviously be untrue, there are continuing fears about whether coffee is actually healthy or not. Google receives 4,400 queries a month about ”why coffee is bad for you” (for context, “why coffee is good for you” gets only 1,300 queries a month).
So with human life extension in mind, I decided to dig into the research. Can coffee consumption actually help spanners extend their healthspan and lifespan? How much is the right dose? How much is too little?
Let’s look at what the research and leading experts say below.
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Coffee extends life in humans (as far as we can tell)
Jamie Hickey, an ISSA-certified nutritionist and founder of Truism Fitness, tells me “coffee has major health benefits that will help you extend your life in a healthy manner.” He points to a 2018 study from JAMA Internal Medicine and explains it in simple terms: “A ten-year study of 37,000 people which found those who drank two cups of coffee every day—without engaging in habits like smoking cigarettes—had a 15% lower death rate than non-coffee drinkers, suggesting that the caffeine protects against early death.” And it’s not the only study of its kind.
For example, a 2019 meta-analysis from the European Journal of Epidemiology looked at “40 studies including 3,852,651 subjects and 450,256 all-cause and cause-specific deaths” and found that two to four cups of coffee a day was associated with reduced all-cause and cause-specific mortality, regardless of “age, overweight status, alcohol drinking, smoking status, and caffeine content of coffee.”
And as recently as spring of 2021, Nutrients published a study that looked at coffee consumption among 1567 participants over an 18-year follow-up period. They found “moderate consumption of coffee, particularly caffeinated coffee (range 1–6.5 cups per day), is associated with a lower all-cause” mortality.
Caffeinated coffee might be protective to overall health, but so is decaf. For example, a 2019 systematic review published in the Journal of Human Nutrition and Dietetics aiming to “investigate the association of caffeinated and decaffeinated coffee consumption and all-cause mortality” found “similar inverse associations [between] caffeinated coffee and decaffeinated coffee [and all-cause mortality.]”
Studies linking coffee to lower all-cause mortality aren’t hard to find—there are 97 studies listed on PubMed on the subject.
Most studies on coffee and longevity are both unfortunately and necessarily epidemiological studies. While I’d love to lock humans in a room and test their response to coffee over the course of decades, it’s not particularly possible (or ethical) to do so. That said, there are a number of randomized control trials showing short-term benefits in humans. For example:
- Decaffeinated coffee improves insulin sensitivity in healthy men
- Coffee abundant in chlorogenic acids reduces abdominal fat in overweight adults
- Coffee antioxidants are strong regulators of oxylipins related to cardiovascular diseases
Further epidemiological and randomized control trials are cited below.
Current research suggests coffee addresses 8 of the leading 10 causes of death in the United States
According to the CDC (and outside COVID times), these are the ten leading causes of death in the U.S. Amazingly, studies have shown that coffee protects against eight of these causes of death. Here’s just one study as an example for each of these ailments, though there are plenty to go around. These causes of death are listed by order of magnitude.
- Heart disease: A 2021 study published in the journal Circulation: Heart Failure found that “the risk of heart failure fell by 5%-12% per cup of coffee per day, compared to people who drank no coffee.”
- Cancer: According to a study conducted by the American Association for Cancer Research, there is substantial evidence that suggests coffee may be “associated with a lower risk of colorectal, liver, female breast and head and neck cancer.”
- Accidents (unintentional injuries): While there are many studies looking at the effects of compounds in coffee as a means to increase focus, I couldn’t find any studies specifically looking at coffee and preventing unintentional injuries.
- Chronic lower respiratory diseases: A systematic review published in The Clinical Respiratory Journal found that coffee was “associated with a reduction in respiratory mortality, and one study found improved lung function in coffee consumers.”
- Stroke (cerebrovascular diseases): A study published in the Journal of Epidemiology & Community Health found that both Japanese men and Japanese women who drank one to six cups of coffee daily were at least 22% less likely to die from cardiovascular disease or stroke.
- Alzheimer’s disease: A population-based CAIDE study found that drinking between three and five cups of coffee a day at midlife was associated with a 65% decreased risk of dementia and Alzheimer’s disease at late-life.
- Diabetes: A systematic review of 13 cohort studies found, “participants who drank 4 to 6 cups and more than 6 to 7 cups of coffee per day had a lower risk of type 2 diabetes compared with those who drank less than 2 cups per day.”
- Nephritis, nephrotic syndrome, and nephrosis: I found no relevant studies.
- Influenza and Pneumonia: A 2021 study published in Nature found that one or two cups of coffee a day had a protective effect against pneumonia among Japanese adults over the age of 65.
- Intentional self-harm (suicide): A study from the Harvard School of Public Health found that “the risk of suicide for adults who drank two to four cups of caffeinated coffee per day was about half that of those who drank decaffeinated coffee or very little or no coffee.”
What about caffeine and decaffeinated coffee?
Dr. Jacob Tiab, MD, of MyLeukemiaTeam, explains how the caffeine in coffee interacts with the human body:
The caffeine in coffee is a central nervous stimulant that works to compete with receptors sites with adenosine. The more caffeine we have in our body, the more it can compete and displace adenosine from central nervous system receptor sites in the brain, leading to increased alertness and attention. As the day progresses, the balance of caffeine and adenosine in our body shifts toward more adenosine, and as more adenosine binds, we begin to get a sluggish, less focused feeling. This is natural and adaptive as our bodies begin to wind down and rest for the day, but you can always get more caffeine to combat this imbalance. However, it may ultimately affect your sleep later in the day.
In other words, when adenosine—which is made in the brain and opens up blood vessels—binds to adenosine receptors, it makes us sleepy. Caffeine binds to adenosine receptors, but it doesn’t slow down the cell’s activity. Instead, caffeine makes the brain’s blood vessels constrict and makes it more difficult for adenosine to attach to adenosine receptors.
Felt effects may include more alertness, wakefulness, restlessness, anxiety, and difficulty sleeping. Caffeine can be habit-forming for some people.
Most studies on coffee look at caffeinated coffee—and many of the benefits, albeit not all of them, appear to stem from the caffeine itself.
Decaffeinated coffee can also cause some problems. Dr. Rashmi Byakodi from Best for Nutrition tells me to watch out for methylene chloride, which is used to decaffeinate coffee. Methylene chloride (otherwise known as “dichloromethane” or DCM) is considered a health hazard. For example, the EU regulating agency Scientific Committee on Occupational Exposure Limit Values (SCOEL) recommends no more than 100 ppm of methylene chloride exposure over the course of eight hours.
Granted, that would require drinking a lot of decaf coffee (eight to ten cups minimum), but it’s not something you want to regularly expose your body to.
Dr. Byakodi points to a few studies showing that decaf coffee might have more DCM than what you’re expecting. “The FDA has approved the use of methylene chloride in the caffeine extraction process as long as the final product contains no more than 10 ppm,” he says. But then he warns, “In decaffeinated coffee, 14 to 15 ppm of methylene chloride level was detected,” citing this study from 1984. Whether or not that study is still relevant has yet to be seen, but it’s a good lesson in being wary of overindulging on decaffeinated coffee.
Of course, a cup of decaf can have some benefits too. For example, decaf coffee has close to the same amount of antioxidants as caffeinated coffee. It’s independently been shown to protect against neurodegenerative diseases. And, according to a 2017 meta-analysis, decaf coffee has been independently shown to protect against certain cancers.
Who should avoid coffee?
There are some groups of people who should avoid coffee.
For example, there are a wealth of animal studies that show excessive caffeine intake can cause problems for fetuses, including premature labor, birth defects, and low-weight offspring. Pregnant women should limit their intake. The American Pregnancy Association writes, “Avoiding caffeine as much as possible is your safest course of action” during pregnancy. Consider switching to decaf or switching to caffeine-free tea for those nine months.
Smokers should be careful with caffeinated coffee. Many of the studies I found and cited above cautioned that smokers were often worse off than the general population after coffee consumption (for example, this study showed that coffee decreases the chance of hypertension except in smokers. For smokers, coffee made their chances of developing hypertension worse). I know smokers don’t need another person telling them that smoking is really bad for them, but coffee is so overwhelmingly good for them that it’s a shame that they’ll miss out on the benefits.
The caffeine in coffee can increase intraocular pressure; people with glaucoma should switch to decaf.
If you have sleep disorders or are susceptible to anxiety, try having your coffee earlier in the morning or switch to decaf.
How much coffee should I drink for longevity benefits?
Erika Gray, PharmD, and chief medical officer at toolboxgenomics.com, gave me a few helpful pointers to optimize coffee consumption for longevity.
She says, “Use L-theanine with your coffee to help support your adrenal glands, decreasing the anxiety or nervousness that can come with coffee. Additionally, L-theanine helps improve the mood and cognitive effects of coffee.” She recommends pairing 100mg with each cup.
Gray also adds, “Some people have cited acrylamide (a byproduct of roasting the coffee beans) as a potentially dangerous substance from animal studies. Ironically, coffee substitutes from rye or chicory were found to have the highest levels of acrylamide, followed by instant coffee and then roasted coffee.” She suggests, “Aim for a lighter roast to decrease acrylamides if you are concerned about the compound.”
Overwhelmingly, researchers found that there are serious benefits to drinking two cups of caffeinated coffee a day. The upper limits on the studies that I looked at varied widely, but generally started tapering off after four or five cups a day.
I, as a 31-year-old female with no contraindications, personally struggle to drink more than a cup of coffee a day without getting jitters. After doing all this research, I am upping my caffeinated coffee intake to two cups a day, but probably won’t increase it more than that. I also plan to switch from medium to light roasts following Gray’s recommendations.
Do coffee drinkers live longer? According to epidemiological studies, yes.
Do you drink coffee or plan to change your coffee consumption habits after reading this article? Is there more that you’d add? Favorite coffee brands?
Let us know in the comments!