As of Friday, March 28, 2014
DEAR DOCTOR K: Is drinking tea good for my health? Which type has the most health benefits?
DEAR READER: Several studies have touted the health benefits of tea, but the benefits of particular foods or drinks are hard to prove.
The most persuasive type of study to prove that any practice has health benefits is a randomized trial. When I say “practice,” I mean a medicine, a surgical procedure, a particular food or exercise routine — any practice designed in part to improve your health. In such studies, some study participants are assigned at random to engage in the practice, and others are not.
While the benefits of a medicine may be apparent pretty quickly, that wouldn’t be true of a food. It might take decades of regularly eating a food to have a positive health effect. That’s one problem. Another is that it’s not really practical to expect that people will deliberately eat (or avoid eating) a particular food, day in and day out, for decades.
However, it still is possible through what are called observational studies to gather strong evidence about the health benefits of foods. And most of the research has found that whether it’s black, white, green or oolong, drinking a few cups of tea a day may help counteract the processes that lead to cancer, heart disease and dementia.
Recently the American Journal of Clinical Nutrition published 11 new studies highlighting the many ways in which tea can may improve our well-being. Here are a few of the results from these studies:
— Tea drinking appears to lower the risk for heart disease and stroke.
— Natural compounds called polyphenols in green tea might protect against several cancers. These include prostate, GI tract, lung, breast and skin cancers.
— Caffeine and antioxidants called catechins found in green, oolong and white teas may increase metabolism and promote weight loss.
— Tea polyphenols may strengthen bones and protect against fractures.
— People who drink tea could see improvements in mood, concentration and performance.
Tea appears to be distinctively rich in certain healthful properties. My colleague Dr. Howard Sesso, associate professor of medicine at Harvard Medical School, explains that tea is particularly plentiful in catechins and epicatechins. These antioxidants are believed to be responsible for many of tea’s health effects.
The less processed tea leaves are, the more health-promoting catechins they contain. Green teas have the most nutritional benefit, followed by oolong and black teas.
Avoid bottled teas, which are often loaded with excess sugar. And don’t heap spoonfuls of sugar into your tea. You can add a little honey or lemon to taste without compromising the purity of your tea. But stop there.
If caffeine makes you jittery or keeps you awake at night, stick to decaf or lower-caffeine varieties, such as white tea.
If you’re just not a tea drinker, don’t despair. The research is still too preliminary to conclude that everyone should regularly drink tea. And if you’re a coffee drinker? Good news: Coffee may protect against Type 2 diabetes and some forms of cancer.
Dr. Komaroff is a physician and professor at Harvard Medical School. To send questions, go to AskDoctorK.com, or write: Ask Doctor K, 10 Shattuck St., Second Floor, Boston, MA 02115.