Often I begin my lectures by asking everyone in the audience who has at least two cups of coffee most days to raise their hands. Usually, the majority of people do so. Then I ask how many of them have at least four cups a day, and fewer hands are raised. Finally I ask how many of them average six or more cups of coffee a day. In response there is always some ner vous laughter and rarely more than a few hands raised.
That’s when I surprise my audience: “Good for you,” I tell those few people. “You’re doing your liver a big favor.”
Coming from me, a liver specialist, that is high praise indeed. In the past, drinking too much coffee supposedly had been linked to a variety of health problems including heart attacks, birth defects, pancreatic cancer, osteoporosis, and miscarriages. We do know that coffee can cause insomnia, tremors, and it can raise blood pressure and increase urination. But more recent evidence indicates that rather than being dangerous, coffee may also offer substantial benefi ts, including protection against heart disease, Type 2 diabetes, liver cirrhosis, Parkinson’s disease, cavities, colon cancer, prostate cancer, and even suicide.
It is known to bring relief for asthma, increase endurance and concentration— some major league baseball players are known to drink as many as six cups of coffee during a game— and increase the absorption of other medications. It can be used to treat headaches— popular over- the- counter pain medications contain as much caffeine per pill as a large cup of joe. And contrary to conventional wisdom, it appears to lower the risk of being hospitalized for an arrhythmia.
What is most surprising is that so few people realize how much value there is in a cup of coffee. Or, in fact, several cups of coffee. According to legend, in about 1000 a.d. the shepherd Kaldi from the province of Kaffa in Ethiopia noticed that the sheep in one pasture were far more active than those in the nearby herds. The cause of that, he determined, were the odd “cherries” they were eating. He tried one himself— and felt its energizing effects. Soon the local monks were using this fruit to help them stay awake at night. Eventually coffee was exported to Yemen and the fi rst known coffee house opened in Istanbul in 1471. Initially, the conservative religious leaders of the Middle East forbade it because of its stimulating abilities, but eventually it spread throughout Europe and became a pop u lar and profi table beverage. By 1675 there were more than 3,000 coffee houses in England.
The health benefi ts of coffee have been debated for centuries. Coffee has been blamed for everything from infertility to causing rebellions. In 1674, for example, English women complained that this “nauseous Puddle- water . . . has Eunucht our Husbands . . . they are become as impotent as Age.” But while many people still believe coffee can be dangerous, numerous large studies indicate that drinking coffee actually provides considerable protection against several serious diseases and— this is even more remarkable—many people should be drinking more coffee, not less.
While most medical studies begin with a specific premise to be tested, considerable information can be gleaned from statistical analysis of information collected with no specific goal. One of the largest of what is most surprising is that so few people realize how much value there is in a cup of coffee. Many people should be drinking more coffee, not less. Those observational collections was compiled by the Kaiser Permanente Medical Care Program. KP had been founded during World War II as a prepayment medical plan for employees of Kaiser Shipyards and expanded coverage after the war. In the 1960s, according to cardiologist Dr. Arthur Klatsky, an investigator at that company’s research division, “Kaiser Permanente began a study to determine which [medical] tests were worth doing and which tests were not. This involved setting up a computerized database to store information from healthcheckup examinations. Although the computers were rudimentary, the database made it possible to perform a study of heart attack predictors matching a wide diversity of known risk factors. The study was conceived by Dr. Gary D. Friedman as basically a search for new heart attack predictors.
“Counting all history queries and mea sure ments, there were about 500 items and some of them would prove predictive of heart attacks. One was that abstinence from alcohol predicted a higher risk from heart attacks compared to light or moderate drinkers. That was not a pre- study hypothesis and it led us to further explore alcohol and health. I was able to obtain grant money to create a new data base about alcohol habits from 1978 to 1985. It consisted of about 129,000 people from a multi- ethnic group. We used that data base to look at subsequent medical events—for example, hospitalization or death from a specific cause, like heart disease or cancer. We published the alcohol– heart attack study in 1974.”
Another study from the same database, first published in 1992 and updated in 2006, reported an inverse relationship between coffee and liver cirrhosis. Coffee lowered the blood level of liver enzymes; astonishingly, the study found that the more coffee people drank, the less chance they would develop alcoholic cirrhosis. Each cup daily accounted for a 20 percent reduction in risk. For example, alcohol drinkers could reduce the chance of cirrhosis by 80 percent by drinking four cups of coffee daily. The reason for this is not known. “Epidemiology doesn’t determine mechanisms,” explained Dr. Klatsky, “it usually shows only associations. I was surprised at the strength of the apparent protection. When you see something that is reduced 60, 70, 80 percent, that is a very major reduction risk. That’s what we found in the relationship between heavy coffee drinking and the likelihood of developing cirrhosis. It’s very important to mention that the best way to reduce the risk of alcoholic cirrhosis is to limit alcohol intake, not to cover heavy drinking by taking coffee.
“I wish we knew a lot more about the coffee- cirrhosis link. We wish we knew what type of coffee people drink, whether they put cream or sugar in it, whether they fi lter it, whether it’s caffeinated or decaffeinated, but all we know is the number of cups per day. We did a subsample of about 10,000 people, and people who drink a lot of coffee, generally four or more cups a day, almost always drink caffeinated coffee.” Personally, Dr. Klatsky states, he has “two cups of coffee in the morning and sometimes a cup at noon, but otherwise it keeps me awake. Three’s my maximum.”
The curious benefi ts of coffee reported in this study may possibly extend to other diseases affecting the liver. In August 2007, the journal Hepatology reported that 10 different studies, conducted in Eu rope and Japan, showed that people who drink coffee have a significantly reduced chance of developing liver cancer. The studies included about 240,000 people, including 2,260 suffering from liver cancer, and showed that people who drank at least several cups of coffee every day had less than half the chance of being diagnosed with liver cancer than study participants who drank no coffee— the odds dropped by 23 percent with each daily cup. As in Dr. Klasky’s study, there was no attempt made to determine the reason for this decline in liver cancer, that’s the type of work done in laboratories by scientists, though there is some speculation that coffee causes liver enzymes to become stronger. It has been my experience— and this is anecdotal evidence— that coffee lowers liver enzymes, which is quite desirable, prevents liver fibrosis (scarring), reduces the rate of hospitalization from chronic liver disease, and reduces the risk of eventually developing liver cancer. We know that coffee is insulin sensitizing; there are people whose pancreas produces sufficient insulin but for some reason it does not have its desired target effect. Coffee sensitizes cells to insulin so that it does have the necessary effect.
Another recent study from the Harvard School of Public Health, Beth Israel Deaconess Medical Center, showed that coffee drinkers have high levels of plasma adiponectin— that’s important because low levels of plasma adiponectin have been linked with aggressive liver disease. And finally, four cups of coffee a day has been shown to reduce the incidence of very painful gout by as much as half.
This impact on insulin may have another vitally important benefit. While previous studies had failed to find a link between coffee drinking and prostate cancer, a National Institutes of Health– funded study published in 2009 followed 50,000 male health professionals for two de cades and found that men who drank six or more cups of caffeinated or decaffeinated coffee daily reduced their chances of developing advanced prostate cancer by 60 percent, men who had four or five cups saw a 25 percent reduction, and drinking up to three cups provided a 20 percent lower risk compared to people who did not drink coffee.
While the reasons for this impact are not known, one of the authors of the study, Harvard’s Kathryn Wilson, speculated, “Coffee has effects on insulin and glucose metabolism as well as sex hormone levels, all of which play a role in prostate cancer.”
If that’s all it did it would still be remarkable, but there is a rapidly growing body of evidence that it has other real benefits. No one can patent coffee, not even Starbucks, so studies about the effects of coffee have to be conducted by large public- oriented groups. Researchers at the Harvard School of Public Health and Brigham and Women’s Hospital conducted their own 125,000-person study from 1980 to 1998, which revealed another impressive benefi t of coffee: People who drink coffee regularly can significantly reduce their risk of Type 2 or adult- onset diabetes. The results were impressive: Men who drank six or more cups of caffeinated coffee daily reduced their risk for this terrible disease by more than 50 percent; women who drank the same amount reduced their risk by almost 30 percent.
Those fi ndings were confirmed by a meta- analysis conducted at Australia’s University of Sydney. A team of international researchers examined 18 studies involving more than 450,000 participants and their meta- analysis found: “Every additional cup of coffee consumed in a day was associated with a 7 percent reduction in the excess risk of diabetes.”
In both of these studies it really was quantity that mattered. In the world of coffee, quality is in the cup of the holder. The philosopher Voltaire was purported to drink as many as 50 small cups of coffee a day— and died in 1778 at age 83. While that certainly seems extreme, in the Harvard study those people who consumed fewer than four normal- size cups daily reduced their risk of contracting Type 2 diabetes only by about 2 to 7 percent. But adults who routinely had four or five cups reduced their risk by 30 percent. And six or more cups? An extraordinary 50 percent. Oddly, that study showed that for women, drinking fi ve or more cups a day provided no additional benefi ts. Like the Australian study, the Harvard study did examine the difference between caffeinated and decaffeinated coffee and found that for men drinking four or more cups daily of decaffeinated coffee reduced the risk of developing diabetes by 25 percent and for women by 15 percent, so clearly there are benefi ts no matter what type of coffee you drink— as long as you drink a lot of it.
Further confirming this link was an 11- year study beginning in 1986 conducted at the University of Minnesota examining the relationship between coffee and diabetes in postmenopausal women. Women who drank six or more cups of any type of coffee were 22 percent less likely to be diagnosed with diabetes than women who drank no coffee. Surprisingly, especially to those people who believe the medicinal value of coffee is derived from its caffeine content, women who drank six or more cups of decaffeinated coffee reduced their risk by 33 percent. The present theory about why there has consistently been a difference in the benefi ts of heavy coffee intake in men and women is that women’s hormones or, more often, hormone- replacement drugs in postmenopausal women, mitigate the effect.
Another analysis, this one conducted by Harvard with researchers working with colleagues from the Universidad Autónoma de Madrid, investigated the link between coffee and strokes in women. Because coffee does stimulate the heart, there has been a supposition that too much coffee might cause heart problems. For that reason it was long believed that drinking a substantial amount of coffee could be very dangerous. In fact, this study showed exactly the opposite effect. Using data from the Nurses’ Health Study, in which 83,000 women regularly completed food frequency questionnaires, including about coffee consumption, for 24 years, researchers discovered that women who drank two or three cups of coffee a day reduced their risk of stroke by 19 percent— and the more coffee they drank the greater the reduction. Women who did not smoke reported even greater benefits; nonsmoking women who drank four or more cups of coffee a day reduced their risk by an amazing 43 percent! This level of risk reduction is on par with the impact of some of the best- selling drugs in the world.
Although the reasons for this are not known, there is some very interesting associated data. It turns out that these benefi ts are not associated with caffeinated tea or soft drinks— and people who drank at least two cups of decaffeinated coffee did show a reduced risk for stroke. According to epidemiologist Esther Lopez- Garcia, one of the directors of the study, “This finding supports the hypothesis that components in coffee other than caffeine may be responsible for the potential benefi t of coffee on stroke risk.” This is an important point: Coffee, like wine, has hundreds of component chemicals, including potassium, magnesium, vitamin E, and antioxidants. It is naïve to believe because coffee does stimulate the heart, there has been a supposition that too much coffee might cause heart problems. In fact, this study showed exactly the opposite effect.
that only one of those substances is some sort of magic bullet. Researchers in the University of Sydney diabetes study reached the same conclusion, pointing out, “Our fi ndings suggest that any protective effects of coffee . . . are unlikely to be solely effects of caffeine, but rather, as has been speculated previously, they likely involve a broader range of chemical constituents present in these beverages, such as magnesium, lignans and chlorogenic acids.” A companion study to the Nurses’ Health Study, published in the Journal of Internal Medicine in 2008, followed more than 40,000 male health professionals for 18 years and concluded that men who drank fi ve cups of coffee a day reduced their risk of dying from heart disease by 44 percent. In fact, men who drank more than fi ve cups of java every day were 35 percent less likely to die from any cause, while women who drank between four and five cups reduced their risk of mortality by 26 percent.
According to a Swiss study, that reduced risk is seen even in people who have suffered heart attacks. The Stockholm Heart Epidemiology Program enrolled more than 1,300 men and women who had a confirmed heart attack between 1992 and 1994. Eight years later those patients who normally drank between one and three cups of coffee daily reduced their risk of death by a third over those people who averaged less than a cup a day, while those participants who consumed four to five cups reduced their risk of suffering a fatal heart attack almost by half.
While it has long been accepted that people with heart arrhythmia should avoid coffee, another Kaiser Permanente long- term prospective study published in March 2010 reported just the opposite. People who drank at least four cups of coffee daily were almost one- fi fth less likely to be admitted to a hospital with a heart rhythm disturbance than non- coffee drinkers. Dr. Klatsky and colleagues analyzed data collected from more than 130,000 people over a seven- year period and found that the reduced risk extended to the various types of rhythm disturbance. Dr. Klatsky admitted that “This [study] is going to surprise people. I think conventional wisdom is that coffee can cause palpitations and it can cause rhythm problems. I think, though, that conventional wisdom is not always right, and the data that were available before this study do not support the idea that moderate amounts of coffee provoke rhythm problems.”
Dr. Klatsky pointed out that “we’re not going to recommend that people drink coffee to prevent rhythm problems,” but that people who drink a moderate amount of coffee can be reassurred they are not increasing their risk of signifi cant heart rhythm problems.”
There may well be even more benefits to drinking a lot of coffee. Both the Kaiser Permanente study and the Nurses’ study indicated that heavy coffee drinkers were less likely to commit suicide and men, but not women, had a reduced risk for Parkinson’s disease. In 2000 the Journal of the American Medical Association reported that a federally funded study of 8,000 Hawaiian men found that those who didn’t drink coffee had double the risk of getting Parkinson’s than men who drank four ounces to four cups of coffee a day. While these links are not as statistically compelling as the reduction in cirrhosis or diabetes, they’re certainly worth considering. Again, no one knows precisely why this is true, but it is known that in Parkinson’s patients the cells that produce the chemical dopamine have stopped working, and caffeine increases the production of dopamine in the brain.
Every year I spend four weeks attending on the hepatology ser vice at Beth Israel Deaconess Medical Center, a major teaching affi liate of Harvard Medical School. For the last several years I’ve been telling every student, resident, and fellow on our liver ser vice to ask all our patients how much coffee they drink. And what I’ve heard, over and over, is that none of these patients with severe liver disease drinks coffee.
It’s remarkable how consistent that has been. But one year, on my last day, a resident approached me smiling broadly and said, “Dr. Chopra, I’ve fi nally got a patient who drinks coffee.”
“Tell me about him,” I said.
“This was a patient admitted with cellulitis. He drinks four cups of regular coffee a day.”
When I took my own history, I asked him, “Please, tell me about tea and coffee.”
“I don’t drink tea,” he said. “But I love coffee.” I asked him if he drank regular or decaf.
I asked him how many cups he drank every day.
What size? “Usual size.”
Then I asked one more question, “How long have you been drinking coffee?”
And matter- of- factly he responded, “Ever since my liver transplant.” Well, no wonder coffee hadn’t prevented his disease. I then asked, “Did someone tell you to drink coffee after your transplant?” He shook his head. “No, but after my transplant I suddenly had this incredible urge to drink coffee.”
Personally, I love coffee and drink about four or five cups a day. Usually with skim milk or black, but no sweetener. My collaborator, Dr. Lotvin, drinks between three and fi ve cups of black coffee daily. Once I was asked to compare the benefi ts of drinking coffee to exercising in patients with Type 2 diabetes. After thinking about it for a moment I said, “They’re both quite beneficial. It seems to me that the best thing to do is run to Starbucks!”
But before you run out and start chugging coffee by the pot please remember that coffee does have some negative effects on a lot of people. It can keep you awake at night. It may be dangerous for people with serious cardiac arrhythmias. It can worsen heartburn and also the symptoms of irritable bowel syndrome. It can raise your blood pressure and make you irritable. And some studies have shown that drinking two or more cups a day does increase the risk of a miscarriage for pregnant women and may result in lower- weight babies. But if you can drink a considerable amount of coffee without any repercussions, some very good studies indicate you may well be adding an additional layer of protection against some very dangerous diseases. If you intend to start drinking, start slow, have half a cup. If there is no problem, have a full cup. See how you feel. And if it doesn’t affect you, go ahead, have another cup.
Dr. Chopra Says:
If you’re like most people, coffee can be very beneficial for you. And more coffee is even better for you. Coffee has been shown to reduce the incidence of several serious diseases. So if your system can tolerate it, enjoy those extra cups of coffee.
PHOTO (cc): Flickr / Teo