Coffee is one of the most widely consumed beverages around the world and there are many studies carried out to investigate its effect on humans, most of which turn out to be positive.
However, considering coffee can contain high levels of caffeine—the main ingredient providing the energy-boosting effects it’s known for—it may potentially be harmful depending on the situation. For example, drinking coffee is not recommended during pregnancy as it may lead to premature contractions.
Looking at hundreds of coffee studies
To investigate the effects of coffee in more detail, the researchers looked at over 200 studies that had aggregated data from observational research and 17 studies that had aggregated data from clinical trials across all countries and all settings.
Their conclusion after looking at the available sources was that drinking three to four cups of coffee a day was associated with a lower risk of death and disease compared to not drinking coffee at all. Coffee was associated with lower risk of dementia, diabetes, liver disease, and even some cancers.
However, because some of the observational studies provided usable but lower quality evidence, no firm cause and effect conclusion can be drawn.
The researchers go on to say that coffee drinking was consistently associated with a lower risk of death from all causes of heart disease. Drinking more than this was not associated with harm, but it did not provide much of an additional benefit.
A multitude of beneficial health associations
Cancers such as prostate, endometrial, skin, and liver were all lower risk in coffee drinkers compared to non-coffee drinkers. Additionally, the risk of type 2 diabetes, gallstones, and gout was also decreased. However, the greatest benefit drinking coffee provided was against liver conditions such as cirrhosis of the liver.
Coffee was even found to have beneficial associations for Parkinson’s disease, Alzheimer’s disease, and depression.
With all of this positive evidence supporting coffee drinking, the researchers stress that their study should be taken with some degree of caution, as some people are at higher risk for adverse effects than others.
“Although we can be reassured that coffee intake is generally safe, doctors should not recommend drinking coffee to prevent disease – and people should not start drinking coffee for health reasons,” said Eliseo Guallar of Johns Hopkins Bloomberg School of Public Health.
Related: Love coffee? You’ll probably live longer