Caffeine is the most commonly used psychoactive drug in the world -- for good reason. It wakes us up, helps us stay on task, and provides an oft-needed energy boost.
And most of us in the Americas and Europe get our caffeine fix from coffee.
But people often worry that they should limit their coffee consumption or cut it out completely. That's probably because coffee can feel like a crutch.
It is possible to overdo it on caffeine --many heavy coffee drinkers surpass the recommended limit of 400 mg of caffeine per day, and that can cause insomnia, restlessness, or a fast heartbeat, especially if consumed too fast.
But most research on coffee consumption indicates that coffee is not bad for us, and is associated with some pretty impressive health benefits.
In most cases we can't say that coffee actually causes health benefits -- the causal mechanism is unclear. But research does suggest that coffee drinkers are less likely to suffer from certain illnesses.
There are plenty of foods and drinks that most of us should consume less. But here's why coffee shouldn't be on that list.
Liver health: A review that combined the results of nine studies found that drinking more coffee is associated with lower risk for cirrhosis.
In the review, drinking one cup of coffee per day was shown to be linked with a 22% reduced risk for cirrhosis, a liver disease that is often caused by heavy alcohol consumption. Two daily cups were associated with a 43% reduced risk, three cups with 57% reduced risk, and four cups with 65% reduced risk.
Heart disease: A review of more than 200 studies found that people who drank three or four cups of coffee per day were 19% less likely to die from cardiovascular disease.
Type 2 diabetes: One large review of studies found that every additional cup of coffee one drinks per day was correlated with a 7% reduced risk for developing Type 2 diabetes.
Cancer: One review found that heavy coffee drinkers (who had at least three cups a day) had an 18% reduced risk for cancer.
Another review found that at least one cup each day was associated with 15% reduced risk for liver cancer and an 8% reduced risk for endometrial cancer.
Some data indicates that coffee drinkers may be less likely to suffer from oral/pharyngeal cancer and advanced prostate cancer as well.
Alzheimer's disease and dementia: A meta-analysis of studies about coffee intake and brain health calculated that regular coffee drinkers were approximately 16% less likely to suffer from Alzheimer's, dementia, or cognitive decline.
There are smaller studies that suggest drinking coffee can lead to even bigger risk reductions for Alzheimer's.
Depression: One large study of more than 50,000 women showed that drinking at least a cup of coffee each week was associated with 15% reduced risk for depression, and drinking two to three cups per day was associated with 20% reduced risk.
Another study that looked at more than 100,000 men and women found that coffee drinkers were 45% less likely to die from suicide and heavy coffee drinkers (four or more cups a day) 53% less likely to die from suicide.
Overall mortality: One large study of more than 500,000 European people found that in a 16-year-period, men who drank three or more cups per day were 12% less likely to die, and women 7% less likely to die.
In particular, people were less likely to die from circulatory and digestive diseases. Heavy coffee drinkers also had healthier livers.
Another study of 185,855 Americans confirmed that result. People who drank one cup per day were 12% less likely to die. Two to three cups were associated with an 18% decrease in risk for early death. (Decaf had the same benefits.)
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