If you drink coffee, I have some bad news and some good news. The bad news is that the more cups of coffee you drink, the higher your risk of dying early. The good news is that if you "risk adjust," then the more cups of coffee you drink, the lower your risk of dying early. Let me explain.
According to a 2012 study in the New England Journal of Medicine, 400,000 AARP members were followed for 14 years, with a close survey of their coffee-drinking habits, diet and death.
Among men who drank six cups or more of coffee, 19 percent died early compared to 13 percent of the non-coffee drinkers. Among women who drank six cups or more of coffee, 15 percent died early compared to 10 percent of non-coffee drinkers. To an untrained person it would seem that coffee was detrimental to our health and we should stop at once.
However, people are more complex. As it turns out, the heavy coffee drinkers tended to be heavy smokers, heavy drinkers and red-meat eaters, all habits that can contribute to an earlier death.
So, in such situations, the statisticians do some "tweaking" to the data, formally called risk adjustment. This means that they take into account the higher risk of dying among smokers, drinkers and red-meat eaters and then they compare the population of coffee drinkers to coffee non-drinkers.
And, voila! The risk-adjusted finding is that drinking coffee not only is not harmful but it actually may be protective, like an aspirin, and it is dose-dependant, which means the more coffee you drink the lower your chances of dying.
For example, women who drank six cups or more of coffee had a 15 percent lower chance of dying early compared with those women who drank no coffee. Those who drank one cup of coffee had a 5 percent lower chance of dying than their non-coffee-drinking counterparts.
So I wondered is this just a play of numbers by statisticians or a genuine scientific finding. I think it is real. To the rejoicing of java drinkers across the world, a Japanese study found nearly a 17 percent reduction in death in those who drank six cups of coffee a day compared to one-cup-a-day coffee drinkers, while a study among health professionals found a 20 percent reduction.
When we look at the data in detail, heavy coffee drinkers had lower rates of heart disease, stroke, respiratory illness, diabetes and infections than non-coffee drinkers. Only cancer deaths were not lower.
You may be wondering what is in the coffee that is so beneficial. It's the caffeine and the antioxidants in the coffee beans. Caffeine is found in medications for Parkinson's disease, asthma, pain and headaches. One cup of drip-brewed coffee has three and a half times the caffeine of a cup of tea.
It's mainly the antioxidants that have the major health benefits, so decaffeinated coffee drinkers need not worry. Antioxidants are chemicals that protect the cells from damage, disease and aging. We are encouraged to eat five servings of fruits and vegetables because of their antioxidant content, but one cup of coffee has more antioxidants than a serving of grape juice, blueberries, raspberries or oranges.
Coffee does have its down side. On a rare occasion, when I sip a cup of coffee I become a bit jittery and have to run to the restroom sooner than planned. For others, coffee causes tremulousness and increases their heart rate and blood pressure.
All this news about coffee is exciting for research scientists at Vanderbilt University's Institute for Coffee Studies. (Honestly, such an institute exists as a division of the Vanderbilt University Medical Center.) They study the potential therapeutic uses of coffee.
One other note: The AARP study was observational, not causal. That is: It does not prove a cause-and-effect relationship. To scientifically prove that coffee reduces mortality rates, we would have to take a group, divide the participants in half, provide coffee to one group and restrict coffee from the other group and then look at mortality rates over 15 years. Obviously, no sane coffee drinkers or nondrinkers would subject themselves to such a study.
Until then, this is the best scientific finding we have, which is good if you are a coffee drinker. So drink up.
For more by Manoj Jain, MD MPH, click here.
For more on diet and nutrition, click here.