Good News on Tea: Few Contaminants, Lots of Health Benefits

Teas made from the tea plant come in four basic varieties: black, oolong, green, and white. They differ in flavor and color depending on how the leaves of the plant are picked, rolled, crushed, and exposed to air before drying.

For example, black teas are exposed to the air for an extended period before being steamed and dried, which promotes oxidation and gives the tea its dark color and deep flavor. Oolong teas are exposed for a shorter time, creating a slightly milder color and flavor. The leaves in green tea retain their color because they’re steamed and dried soon after picking, preventing most oxidation, so green tea has a grassier, more herbal flavor. White teas are even lighter in color and flavor because they’re made from young tea buds that are steamed and dried immediately after picking.

In addition to the obvious differences in color and flavor, there are some differences in health effects. Most notably, the darker the tea, the higher the caffeine level tends to be. An 8-ounce cup of black tea, for example, usually has about 40 to 60 milligrams of caffeine, about half of what’s in a typical cup of brewed coffee and about twice as much as what’s in green tea.

While caffeine can promote alertness, too much can make you jittery and possibly pose other health risks. That’s why the Food and Drug Administration recommends consuming no more than 400 mg of it per day. If you are watching your caffeine intake, then, you may want to drink more green tea, for example, than black. Note, though, that how much caffeine ends up in a cup of tea can vary from product to product, and also depends on how long you let it steep. So monitor how you feel after drinking your tea and adjust accordingly.

There are also some subtle differences among tea types in the amounts of antioxidants—a broad class of substances that offer a multitude of health benefits—they contain. But overall, they are all excellent sources of those beneficial compounds, says Michelle Francl, PhD, professor of chemistry at Bryn Mawr College in Pa., who’s also the author of the book “Steeped: The Chemistry of Tea” (Royal Society of Chemistry, 2024). “Even though we tend to think of green tea as kind of healthier than black tea, the [antioxidant] profiles are practically all the same,” she says.

Here’s a quick rundown of tea’s likely health benefits and the compounds thought to contribute to them.