When it comes to your heart, coffee has taken a couple of lumps in the past year, although in a recent large study it got a clean bill of health. Tea, on the other hand, consistently is portrayed as a heart-healthy beverage, although the Food and Drug Administration recently denied that claim once again.
Coffee and tea have been studied intensely in the past several years, and while medical science has not definitively decided how the popular beverages affect the heart, it is inching closer to a conclusion.
This year, two studies suggested that the less coffee a person drinks, the better.
In March, a study that followed more than 3,000 coffee drinkers in Greece for two years found troubling levels of inflammatory substances in their blood, compared with the blood of those who don't drink coffee.
In other studies, those substances have been associated with higher rates of heart attack and stroke, although the new study did not assess whether the coffee drinkers were at more risk.
The study, which was presented at the American College of Cardiology annual meeting, found that men who consumed more than a cup of coffee a day had 30 percent higher levels of a particular inflammatory substance in their blood, compared with noncoffee drinkers. For women, it was 38 percent higher.
Various other inflammatory substances also were elevated in the coffee drinkers.
"Maybe [coffee] is harmful when you consume high quantities," said lead author Christina Chrysohoou, a cardiologist with the First Cardiology Clinic at the University of Athens in a March interview. "Moderate consumption is the best."
Just before that study, another one found a troubling link between coffee consumption and nonfatal heart attacks in patients who had a specific genetic trait related to how quickly they metabolized caffeine. About 50 percent of the U.S. population has that trait.
That study, published in March in the Journal of the American Medical Association, involved 2,014 first heart-attack patients in Costa Rica.
Those who slowly metabolized caffeine and who drank two to three cups of coffee a day had a 36 percent greater risk of having a nonfatal first heart attack. For those who drank four or more cups, the risk was 64 percent greater.
However, for those who were genetically predisposed to rapidly metabolize caffeine, drinking up to three cups of coffee a day brought as much as a 22 percent reduction in heart-attack risk.
More reassurance came from a huge prospective study published in May that essentially gave coffee, at least filtered coffee, a clean bill of health.
The study, which followed 128,000 men and women for up to 20 years, found no evidence that coffee drinking increased the risk of coronary heart disease.
"We basically have cleared coffee's name," said senior author Dr. Frank Hu, an associate professor of nutrition and epidemiology at the Harvard School of Public Health. "There is no hint of increased risk."
In fact, those who drank more than six cups a day had a reduced risk of heart disease, according to the study published in Circulation, a journal of the American Heart Association.
"We don't want to make too much of that," warned Hu, who said that finding could be due to chance.
Hu noted, however, that other research suggests coffee might protect against diabetes, Parkinson's disease and gallstones. Last month, a separate study in the Archives of Internal Medicine found that coffee may help prevent the liver disease alcoholic cirrhosis.
"It seems that coffee is more helpful than harmful," Hu said.
One caution, he said, is that boiled, unfiltered coffee may increase cholesterol, but nearly all coffee in the United States is filtered.
Hu said the other big concern is high-calorie and high-fat coffee drinks.
"Too much sugar and cream may create some health concerns," he said.
While coffee appears to be fairly benign toward the heart, there are other reasons to limit consumption, said Dr. Paul J. Millea, an assistant professor of family medicine at the Medical College of Wisconsin.
It can contribute to ulcers and gastroesophageal reflux disease, he said.
Beyond that, drinking large amounts of coffee may be a sign of another concern.
"If we are downing multiple cups of coffee a day, why is it?" he said. "Usually it's because of some hyperstressed lifestyle."
He recommends limiting consumption to one to two cups a day.
But what about green tea?
Last month, researchers at Yale University School of Medicine weighed in on the issue with a review article that looked at more than 100 studies on the health benefits of green tea.
More studies are needed, they said. But they pointed to what they called an "Asian paradox," which refers to lower rates of heart disease and cancer in Asia despite high rates of cigarette smoking.
They theorized that the 1.2 liters of green tea that is consumed by many Asians each day provides high levels of polyphenols and other antioxidants.
These compounds may work in several ways to improve cardiovascular health, including preventing blood platelets from sticking together and improving cholesterol levels, said the researchers, whose study appeared in the May issue of the Journal of the American College of Surgeons.
Specifically, green tea may prevent the oxidation of LDL cholesterol (the bad kind), which, in turn, can reduce the buildup of plaque in arteries, the researchers wrote.
It may be difficult for Americans to consume as much green tea as Asians, but they can get greater amounts of antioxidants in their diet by drinking some green tea, as well as increasing consumption of dark fruits and vegetables, drinking moderate amounts of red wine and even eating some dark chocolate, said lead author Bauer Sumpio, a professor of vascular surgery at Yale.
"The collective intake probably is of significant protection to cardiovascular disease," he said.
Sumpio said what swayed him is laboratory research on cells showing that green tea can act in a way that prevents heart disease and cancer.
"For me, there is no downside to drinking green tea," he said. "It's not like red wine with the alcohol issue."
Sumpio and his co-authors concluded in the article that "the evidence is strong that green tea consumption is a useful dietary habit to lower the risk [for] and treat a number of chronic diseases. ... The consumption of six to 10 cups of tea per day might constitute an aid to increased health, longevity and quality of life."
However, the FDA isn't convinced.
After reviewing 107 studies, it recently concluded that there was no credible evidence to support the claim that green tea reduced cardiovascular disease risk factors.
The statement came in a letter denying a request by a tea company to make heart health claims about green tea.
The problem with many tea and coffee studies is that they usually look for associations between the beverages and heart disease risk, said James Stein, a cardiologist with the University of Wisconsin Hospital and Clinics.
Coffee and tea drinkers may be more likely to engage in other activities that can affect their heart health. For instance, coffee drinkers are more likely to be smokers. Green tea drinkers may be more likely to eat lots of fruits and vegetables.
In countries such as Japan, green tea drinkers also may consume much higher amounts of raw fish or foods such as seaweed, added Millea of the Medical College.
Researchers try to adjust for those and other activities, but it is difficult to correct for everything that might have an effect.
And the studies do not assess individual susceptibility to the effects of caffeine, said Stein, an associate professor of cardiovascular medicine.
Clearly some people are better off if they do not consume caffeine, he said. That includes people with heart disease, high blood pressure and people who have had strokes.
Caffeine, at least in the short term, raises blood pressure and heart rate and can constrict arteries, he said.
Caffeine "could precipitate a plaque rupture and lead to heart attack," Stein said.
Stein acknowledged that coffee contains flavonoids that have been associated with better heart health, but he tells his patients to limit their coffee to one cup a day.
He said the research on green tea looks promising, but has yet to prove a clear heart benefit, although it certainly is healthier than drinking soda, he said.
"We've been arguing for two decades whether caffeinated [coffee] is better than decaf and whether green tea is better than black," he said. "We don't know if long-term use is really helpful or not.
"The conservative approach [drinking these beverages in moderation] will be the prevailing dogma for quite a while."