People who drink a moderate amount of coffee each day are more likely to experience health benefits than harms, cutting their risk of premature death and several illnesses, according to a study published in BMJ.
For the study, researchers from the University of Southampton in the United Kingdom assessed meta-analyses of 201 observational studies, as well as 17 clinical trials, to determine the health effects of drinking coffee regularly.
The researchers found that drinking coffee was linked to a lower risk of developing:
- Cancer, including endometrial, prostate, and skin cancer;
- Cardiovascular disease;
- Liver disease;
- Parkinson's disease; and
- Premature death.
Overall, the researchers found that individuals who drank three to four cups of coffee each day experienced the greatest health benefits compared with individuals who did not drink coffee. The researchers added that while benefits appeared to taper beyond three to four cups, individuals who drank up to seven cups of coffee still appeared to benefit.
However, the researchers cautioned that women who are pregnant or have a higher risk of suffering fractures should limit their caffeinated coffee intake.
The researchers also said that coffee drinkers should stick with "healthy coffees" without extra cream, milk, or sugar.
According to the researchers, the findings supporting moderate coffee consumption are significant because "coffee is one of the most commonly consumed beverages worldwide," which means that "even small individual health effects could be important on a population scale."
The researchers said while it's "difficult" to know exactly why coffee has a positive effect on health, its benefits could be linked to coffee's antioxidants and anti-fibrotics, which block or slow cell damage.
The researchers cautioned, however, that the results were mostly observational, so no firm casual connections between coffee and health could be drawn from the results.
Paul Roderick, a co-author of the study and a member of the faculty of medicine at the University of Southampton, pointed out that other factors, such as age, smoking status, and level of exercise, "could all have had an effect." However, he said the fact that this study backs up previous research about the health effects of coffee is reassuring. "There is a balance of risks in life, and the benefits of moderate consumption of coffee seem to outweigh the risks," he said.
In an accompanying editorial, Eliseo Guallar of the Johns Hopkins Bloomberg School of Public Health said that it is impossible to know whether coffee truly prevents chronic diseases or reduces mortality because of all the related factors that could play a role, such as why someone began drinking the beverage or what type of coffee someone drinks. Guallar advised against doctors recommending that patients start drinking coffee to prevent diseases.
Tom Sanders, professor emeritus of nutrition and dietetics at King's College London, also cautioned against coffee as a preventive measure. "Coffee is known to cause headaches in some people and it also increases the urge to go to the toilet—some people chose not to drink coffee for these reasons," he said. "Patients with abnormal heart rhythms are often advised to drink de-caffeinated coffee. Caffeine also acutely increases blood pressure, albeit transiently" (May, USA Today, 11/23; Kelland, Reuters, 11/22; Meredith, CNBC, 11/23; Roxby, BBC News, 11/23).
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