Two recent large studies suggest it might have been coffee that bubbled from the fountain of youth.
Both studies, one conducted in the United States, one across 10 European countries, found that people who drank even a single cup of coffee a day — decaf and/or caffeinated — lived longer than people who didn’t drink any coffee.
The effects were modest; compared to non-coffee drinkers, those who quaffed the most in the U.S. study, four or more cups a day, had an 18 percent lower risk of dying by its end. But given that half of U.S. adults drink coffee every day, the impact on the population could be substantial.
The research couldn’t prove that coffee deserved the credit for imbibers’ additional birthdays, because the studies were observational, which means participants chose whether they wanted to drink coffee. Maybe some other characteristic of coffee drinkers explained why they lived longer.
Researchers did account for known confounding factors such as smoking, because previous studies have shown that smokers are more likely to drink coffee than non-smokers. But there could have been other, unidentified factors related to drinking coffee that affected their results.
Can You Brew Better Health?
Still, the consistency of findings across different ethnic groups in the U.S. study and different methods of preparation in the European study — espressos in Italy, watered down coffee in Scandinavian countries — adds credence to the notion that coffee protects against many of the leading causes of death.
And as a trio of Johns Hopkins University scientists wrote in an editorial accompanying the two papers, “a protective effect of coffee is biologically plausible.” The studies and the editorial were published online Monday in the Annals of Internal Medicine.
“Coffee is a rich source of various compounds that have biological activity,” Marc Gunter, lead author of the European study, said in an email. ”Many of these have antioxidant and anti-inflammatory properties.” Gunter heads the Nutritional Epidemiology Group at the World Health Organization’s International Agency for Research on Cancer in Lyon, France.
Caffeine Not the Deciding Factor
Caffeine has been the most studied compound in coffee, but it didn’t appear to make a difference in either of the studies. Perhaps it’s a combination of compounds in coffee, not any individual compound, that might be beneficial, said Veronica Setiawan, senior author of the U.S. study and an associate professor of preventive medicine at the Keck School of Medicine at the University of Southern California. “We can’t tell from this particular study.”
Setiawan’s study followed more than 185,000 African-Americans, Native Hawaiians, Japanese-Americans, Latinos and whites for an average of 16 years. Little previous research had examined the effect of drinking coffee in people who weren’t white, the coauthors wrote.
“I’m actually very reassured that you see similar findings in non-white populations,” Setiawan said in an interview. “There’s something going on in coffee.”
Deaths from Digestive and Circulatory Causes
The European study, whose authors say is the largest ever of its kind, followed more than half a million adults, mostly aged 35 and older, for an average of about 16½ years. Researchers found that the more coffee people drank, the less likely they were to have died by the end of the follow-up period. The biggest difference was in rates of deaths from digestive and circulatory diseases.
Besides asking participants about how much coffee they drank, a randomly selected group of 14,800 participants in the European study underwent a blood test at the beginning to analyze levels of biomarkers, which are substances linked to health.
“We see in our study that people consuming coffee had lower levels of inflammatory factors and glucose (sugar) as well as healthier liver enzyme profiles,” Gunter said. “We need more research to identify the beneficial compounds in coffee, and a study such as this will probably stimulate research in this.”
Question About Ovarian Cancer
While the studies can’t confirm that coffee lowers the risk of dying, for the most part they found no indication that drinking coffee might hasten death. Gunter’s study did find that women who drank coffee were more likely to die of cancer during the follow-up period than non-drinkers, which might sound scary. But that finding was primarily driven by a statistically significant association between drinking coffee and risk of death from ovarian cancer.
“To our knowledge, there is no prevailing hypothesis as to why coffee drinking should increase the risk of death specifically from ovarian cancer,” Gunter and his coauthors wrote, noting that their finding could be false. One other study that followed people over time also found an association between coffee drinking and an increased risk of dying from ovarian cancer, but two other such studies did not, the researchers said.
Limitations of the Studies
As with most studies, especially those that are observational, the new coffee studies have limitations that could have affected their findings. There’s the aforementioned issue of unknown confounding factors, of course.
Plus, the researchers asked participants only once, at the beginning of the study, about how much coffee they drank. Their habits could have changed over the years, and/or they might not have accurately quantified their coffee habit in the first place. But, Setiawan said, previous research has shown that people’s coffee-drinking habits don’t change much over the course of a decade.
Neither of the researchers is suggesting that non-drinkers start guzzling java for its health benefits. Setiawan says she consumes a cup of coffee or two a day, although her research suggests drinking four cups a day might be even more beneficial. For her, two cups daily is enough.
“I’m not sure there’s enough evidence to support non-coffee-drinkers start drinking coffee — yet,” Gunter said. “I drink coffee, but tea too. I’m English!”
For a Q&A about the coffee studies, check out a patient summary on the journal’s website.
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