Millions of people around the world depend on a cup of coffee to start their day. We treat ourselves to a nice, hot, smooth cup and enjoy our vice even if it’s bad for you. Or… is it?
Is Coffee bad or good for you? Recent studies have evidence that coffee has potential health benefits. While more research is needed to validate the results, the evidence does show potential benefits to drinking coffee.
Lowers risk of Death
Several studies suggest an association between coffee consumption and a lower risk of death. A trial of 185,000 individuals who identified as African American, Latino, Native Hawaiian, white, or Japanese American, and aged 45-75, were followed over a period of 16.2 years. Coffee was associated with a lower risk of death even after adjusting for confounders. The association was found for both decaffeinated and caffeinated coffee, as well as anywhere from 1 cup per day to 4 cups per day.
In one cohort study, more than 500,000 individuals from 10 countries were followed over a mean period of 16.4 years. Compared to nondrinkers, men who drank the most coffee had a 12% lower risk of death (OR 0.88; 95% CI 0.82-0.95, P<0.001) and women had a 7% lower risk of death (OR 0.93; CI 0.87-0.98, P=0.009). Unfortunately, this study had potentials problems that made the evidence less cleared such as the authors noted that coffee drinking habits were only assessed once, and reverse causality might have affected the findings. However, the large numbers enrolled in the trial and exclusion of those who died within 8 years after the start of the trial certainly strengthen the findings.
Lower risk of developing Diabetes
The Nurses Health Study group had a combined follow-up for individuals of 1,663,319 years and found that those who drank coffee had a lower risk of developing diabetes. Those who decreased their coffee intake by more than 1 cup per day increased their risk for developing diabetes by 17%. They investigated tea drinking but found no association. Diet was reassessed every four years using a questionnaire.
Decrease Mortality in Chronic Kidney Disease (CKD)
Because the caffeine in coffee can transiently increase blood pressure, there are concerns that CKD or heart patients should not drink non-decaffeinated coffee. One group followed more than 2,300 patients with CKD and coffee drinking was associated with a decrease in mortality in that group, independent of many potential confounders (eGFR, smoking status, race, income, hypertension, BMI, and others). Those who drank the most coffee had a 24% lower risk of death compared to nondrinkers. This study at least demonstrates that coffee is safe in this population and that it might be beneficial. It would be interesting to see a similar design with a larger number of people to see if that same association holds true.
Lower risk of Colon cancer
A group studied the association between coffee consumption and colorectal cancer among 5,145 cases and 4,097 controls. In one of the strongest associations of any of these trials, coffee was associated with a 26% overall lower risk of developing colorectal cancer. Among the highest group of consumption (>2.5 servings per day), coffee was associated with a 54% lower risk (OR 0.46; 95% CI 0.39-0.54, P<0.001). Coffee data was collected using a validated questionnaire and the researchers controlled for race. The findings held true for both colon and rectal cancers.
Drink it black and don’t drink it scalding hot. Sugar is associated with numerous health problems and could be ruining the benefits you are receiving, while WHO’s International Agency for Research on Cancer issued a statement in 2016 that there is some limited evidence consuming drinks hotter than 200 degrees Fahrenheit might increase the risk for esophageal cancer.
Why do some think coffee is not good for you?
There have been some concerns that coffee might be bad for you, but these are based on limited evidence or taken out of context. For example, there is an ongoing court battle in California about whether coffee should be labeled a carcinogen due to trace amounts of acrylamide. This is based on the effect of acrylamide alone in animal studies. Other concern is cafestol, a compound removed by paper filters but not by other methods (French press, Turkish coffee), which increases cholesterol. Based on current evidence, the presence of this compound does not appear to negatively affect outcomes.
For people with borderline or high blood pressure, I would cautious and recommend limiting the number of coffee cups to two per day of noncaffeinated coffee. More research is needed to conclusively state some of the above benefits but for now the data is showing that there might be some benefit.
