Dec. 23, 2016 -- A hot cup of coffee can perk you up in the morning. A soothing cup of tea can help you relax after a stressful day. And the latest research about the health benefits of each might help you feel a little better about them, whichever beverage you drink.
After years of studies that seemed to swing between dire warnings and cheery promises about what our favorite caffeinated beverages do and don’t do, much of the recent science regarding coffee and tea is generally positive.
The WHO’s International Agency for Research on Cancer recently took coffee off its list of suspected carcinogens, and some research suggests it could help keep colon cancer from coming back after treatment. Other studies suggest drinking coffee might stave off Alzheimer’s and Parkinson’s diseases.
Various studies have pointed to tea drinkers having lower odds of skin, breast, and prostate cancers. Researchers are still trying to pinpoint the exact ways that happens. But tea, particularly green tea, is rich in compounds like antioxidants, which can limit cell damage and boost the immune system; and polyphenols, which have been shown to lower blood pressure and cholesterol. It also may help stave off Alzheimer's disease through a polyphenol known as EGCG, which prevents the formation of plaques that are linked to that brain-damaging illness.
Is one better for you than the other?
Experts say that’s hard to say. That’s because it’s difficult to separate out their different ingredients, their role in your diet, and their effects on different body systems.
“I think people are looking at both coffee and tea and how they affect everything, including cancer and GI disease and cardiovascular diseases,” says Elliott Miller, MD, a critical care medicine specialist at the National Institutes of Health.
Miller and his colleagues recently looked at signs of heart disease in more than 6,800 people from different backgrounds across the country. About 75% drank coffee, while about 40% reported drinking tea. Drinking more than one cup of tea regularly was linked to less buildup of calcium in arteries that supply blood to the heart, a development that can lead to heart disease.
Coffee didn’t have an effect either way on heart disease, but that was significant in itself, Miller says.
“Very often patients will ask their doctors, ‘Hey, doc, I’ve got coronary artery disease, or I’ve got risk factors like high blood pressure or cholesterol. Is it safe for me to drink coffee?’ Because everyone thinks drinking coffee makes your heart excited and is potentially bad,” Miller says. “So finding that it’s neutral, I think, is pretty important.”
Researchers say it’s hard to pinpoint exactly how both drinks affect health. Both coffee and tea are “complex beverages” that contain a variety of ingredients. They include caffeine, polyphenols, and antioxidants -- compounds researchers are studying for their potential cancer-fighting properties, says Lisa Cimperman, a clinical dietitian at University Hospitals Case Medical Center.
“It’s more of a dynamic interaction than one single compound,” Cimperman says. Some people have tried to isolate one element in tea or coffee that they think is the secret to one effect or another, “and then they realize that it doesn’t have the same effect.”
Cimperman said drinking tea has been linked to lower risks of cancer and heart disease, improved weight loss, and a stronger immune system. Meanwhile, studies point to coffee as a potential way to head off not just Parkinson’s but type 2 diabetes, liver disease, and heart problems, Cimperman says.
Another recent study, led by Charles Fuchs, MD, director of the Gastrointestinal Cancer Center at Boston’s Dana-Farber Cancer Institute, found regular coffee drinking may help prevent colon cancer from coming back after treatment.
In his study of nearly 1,000 patients, Fuchs says, there was a “significant and linear” association between drinking coffee and lower risk of colon cancer returning in those who drank four or more cups a day. “The more coffee they drank, the lower risk of recurrence.” But the researchers aren’t clear on which element of the drink contributed to that result, and there didn’t seem to be any effect from drinking tea, he says.
“I think you can have two or more cups a day without any concern, and certainly that may benefit you,” Fuchs says. But what about for those who don’t drink coffee? “If it was somebody who hates the stuff and asks, ‘Should I drink it?’ I’d say no. I’d counsel them about diet and exercise and avoiding obesity as measures I think would have a similar benefit.”
Other researchers are asking questions about what role genetics and lifestyle play into the effects of drinking coffee or tea. For instance, coffee and cigarettes once went together like ... well, like coffee and cigarettes, which cause cancer and heart disease.
Some people’s bodies process coffee differently than others, says Martha Gulati, MD, head of cardiology at the University of Arizona College of Medicine in Phoenix. Meanwhile, a preference for tea over coffee might reflect other healthier behaviors, she says.
“Does someone who drinks tea do yoga or meditation more?” Gulati says. “I’m not necessarily saying they’re associated, but do they exercise more? Are they drinking things like green tea to maintain their weight better than other types of drinks?”
And Robert Eckel, MD, an endocrinologist at the University of Denver, says an overall heart-healthy diet is “probably the most important aspect” of preventing heart disease.
There are other variables. The WHO’s ruling on coffee nonetheless cautioned that any kind of extremely hot drinks could raise the risk of esophageal cancer, while Cimperman says dumping a lot of cream and sugar into your drink can blunt any benefits.
“No one beverage or food will make or break your diet,” she says. “The quality of your diet is always the sum of all the parts.”