Dear Doctor: I'm only 22 and already I've gotten whiplash from all the studies about coffee. First it's bad for you, then it's good. Then, oops, no -- it's actually bad. My girlfriend's a serious coffee drinker, and she's thrilled about another new study that says coffee's going to help her live longer. Is that right? How do we know what to believe?
Dear Reader: We agree that the back-and-forth about coffee over the decades has been confusing and for coffee drinkers who want a final answer, frustrating. Part of this is because of the nature of ongoing research, which, as it asks new questions, incorporates the newest data. Add enough variables to any line of inquiry, and chances are quite good that the conclusions will shift, if not change.
Another factor that plays a role is the study itself. Many of the coffee studies, including this latest one, have been observational studies. That means that researchers gather data from large populations, identify and account for lifestyle or environmental factors that could sway results, then analyze the resulting data to draw conclusions. When they're finished they have a correlation, but not a definitive cause. That doesn't mean such studies should be discounted. Far from it. It was through observational studies that researchers first linked smoking to lung cancer. This in turn led to the more rigorous and targeted research that revolutionized how we view tobacco and tobacco products.
We suspect that coffee is the subject of so many studies for a couple of reasons. First, it's so widely consumed. Here in the United States, it's our favorite beverage. We drink more coffee than soda, tea and juice combined. Plus, thanks to its caffeine content, coffee is a stimulant. In fact, caffeine is the most widely consumed physiological stimulant in the world. That's why, with regular use, it can result in a mild form of physical dependence. In addition, caffeine has been associated with adverse side effects in some individuals, such as temporary spikes in blood pressure. All of this -- widespread use, potential physiological effects, as well as the numerous bioactive compounds that it contains -- have made coffee a prime target for research. Which brings us to the new study now making headlines.
Researchers in Britain looked at a decade's worth of health data for about 500,000 adults who regularly drank from one to eight cups of coffee per day. This included brewed and instant coffee, as well as decaf. According to their analysis, those who drank coffee regularly had a slightly (emphasis is ours) lower risk of death than did non-coffee drinkers. Although the study didn't address questions of how or why, the researchers have cited coffee's complexity.
In addition to the caffeine that reels us in, coffee contains over 1,000 different chemical compounds, including B vitamins, potassium, magnesium, as well as hundreds of phytochemicals with antioxidant and anti-inflammatory properties. However -- and this is important -- if you're not already a regular or heavy coffee drinker, don't dive into the deep end with a multi-cup habit. And when it comes to pregnant women, the consensus is clear -- severely limit (or quit) coffee. That's because the enzyme needed to metabolize caffeine is not present in the fetus.
(Send your questions to email@example.com, or write: Ask the Doctors, c/o Media Relations, UCLA Health, 924 Westwood Blvd., Suite 350, Los Angeles, CA, 90095. Owing to the volume of mail, personal replies cannot be provided.)