Coffee has a long and fascinating history, but sometimes it has been cited as a cause of disease. However, new research suggests there may actually be health benefits to coffee, when drunk in moderation.
Legend has it that an Ethiopian shepherd noticed his goats were more lively after eating coffee berries, so he tried some himself. Around the year 1100, coffee cultivation began on the Arabian peninsula. Dr. Lenore Arab of the University of California medical school in Los Angeles, says that in the 16th century, coffee was regarded with suspicion by the Christian establishment, then led by Pope Clement VIII.
"The pope was asked to condemn coffee because the Muslims were consuming it, and they thought it must be the drink of the devil. But he actually decided after trying it that this was a wonderful beverage and he actually blessed the coffee and decided that this was very useful because it kept the monks awake during their long vespers [evening prayers]."
Concerns have lingered however, that coffee poses health risks. Loaded with caffeine, coffee is a natural stimulant. Drinking too much can make you feel edgy, nervous, jittery. Coffee can raise your blood pressure, and caffeine is slightly addictive. But recent research has found that moderate coffee drinking - a few cups a day - can actually have some beneficial effects, and might even help reduce the risk of some serious diseases.
Dr. Rob van Dam of the Harvard School of Public Health has been studying the link between coffee - both regular and decaf - and diabetes.
"I think about 16 prospective studies around the world have now looked at coffee consumption in relation to Type II diabetes, and they consistently show that people who drink more coffee - [we're] talk[ing] about four or five cups a day - have a low risk of diabetes. We're also looking at what components of the coffee could be responsible for that. I think so far we have very consistently seen that associations are the same for decaffeinated coffee and caffeinated coffee."
Van Dam was among several coffee experts who spoke this week at the Experimental Biology conference here in Washington. He says a big challenge to researchers is separating out the effect of coffee from other risk factors, such as weight, diet or exercise.
"That's a very important consideration in this type of research. We see actually that people who drink more coffee are less health conscious, and they have a worse diet, and they smoke more, and they tend to have a somewhat higher body mass index. So actually, when we control for these factors more completely, we see a stronger effect, rather than a weaker effect."
Van Dam says some research has identified components in coffee that might be responsible for the effect. If that's confirmed, special coffee blends rich in those components might be marketed for diabetic consumers.
There have also been reports over the years that coffee might cause cancer. Some two decades ago, a study suggested a link between coffee and pancreatic cancer. But Dr. Arab, the UCLA epidemiologist who gave us some coffee history a few moments ago, says hundreds of studies since then have shown that coffee drinkers are less likely to get certain types of cancer, starting with colorectal cancer.
"There might be a 24 percent reduction with regular and higher consumption of coffee. There is also surprisingly interesting and consistent results with liver cancer, that is protective to the extent that drinking coffee regularly in Japan appears to be associated with a 50 percent reduction, and there's a dose-response [relationship] in some of the studies. It's gone down as far as a 70 percent reduction in those drinking more than five cups of coffee a day."
Not all cancers respond in the same way. Arab says there are some studies indicating that a pregnant woman who drinks coffee may put her unborn child at greater risk for childhood leukemia. Coffee may also increase the risk of stomach cancer.
Part of the challenge facing researchers is quantifying coffee consumption. Blend, brewing method and strength are some variables. Espresso, for example, is quite different from filter coffee. Also, a "cup" is the standard measure, but there is no standard cup. One restaurant may serve a 150-milliliter cup, while at many American coffee shops, a cup three times that size is only called "medium." And according to James Coughlin, a scientist and consultant to the industry, the chemistry of coffee itself is enormously complex.
"I'm a chemist and a toxicologist, and I've studied the chemistry of coffee in very good detail. There's at least 2,000 components, individual chemical components, in coffee, which makes it difficult when we're looking at some of the positive beneficial health effects - we're trying to figure out what's in there that could be contributing to that story."
Experts recommend that like so many other things, coffee should be enjoyed in moderation. Drink much more than a liter a day, they say, and you may have to balance some of coffee's benefits with a risk of irritability, nervousness, and perhaps an upset stomach.