What's the best tea for your health? Research points to green tea, although black tea and oolong tea are close.

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Regular tea-drinkers get more from their brew than a relaxing daily ritual and a hit of caffeine to spark the brain. Tea is laced with chemical compounds (phytochemicals) with well-documented anti-inflammatory and antioxidant properties. For overall benefit and supporting science, the best tea to drink is the green variety, although black tea and oolong are close runner-ups.

Tea’s plant-derived phytochemicals pack a health-promoting punch, per published research. Keep in mind, though, that many of the studies have important limitations. On the other hand, tea is relatively cheap (unless you’re a connoisseur) and it poses few risks beyond a case of the caffeine jitters if you drink too much. Think of tea as a pleasurable addition to an overall healthy diet and lifestyle, rather than a panacea for specific health risks and conditions.

How Are Teas Different?

Black, green, and oolong are the most commonly consumed teas made from the leaves and buds of the Camellia sinensis shrub, native to China and India. The harvested leaves are processed to different degrees with fermentation and drying to produce the different tea varieties. Black tea is the most processed; green tea is the least processed; and oolong lies somewhere on the scale between black and green.

Tea ends up with concentrated amounts of flavorful natural oils and aromas—and caffeine, of course. Black and green teas both contain 20 to 45 milligrams (mg) of caffeine. The average dose in coffee is about twice that (95 mg).

Herbal teas are a different matter (see sidebar below). Many are not technically tea—they are “infusions.” That means you take dried stuff and soak it in water to extract whatever’s inside. Herbal teas may contain dried flowers, buds, roots, leaves, grass, bark, seeds, or spices.

Why Is Tea Healthy?

The chemical connection between tea and health is thought to be a group of plant chemicals called polyphenols. They are also abundant in other health-promoting foods, including fruits, vegetables, whole grains, and cocoa. More than 8,000 different types of polyphenols have been identified.

Two types of polyphenols, catechins and epicatechins, are especially abundant in tea. (You may see catechins and epicatechins referred to as flavonoids, which are a sub-type of polyphenols.) Levels of polyphenols are highest in green tea, which is less processed than are black and oolong. The catechins and epicatechins in green tea may also be easier for the body to absorb than other phytochemicals in this group.

Some laboratory research has shown that polyphenols are antioxidants that neutralize potentially harmful substances produced during normal metabolism. Oxidants are waste products and all natural, but if they build up to high levels can harm body tissues.

What’s the Evidence?

Tea, particularly green tea, is a rich source of plant chemicals that you obtain from an overall healthy diet with lots of fruits and vegetables, whole grains, nuts and seeds, and legumes. It’s no surprise that regularly imbibing tea has been linked to lower risk for major chronic diseases, including cancer.

Some of the best evidence for tea’s benefits comes from large, decades-long observational studies based at Harvard University: the Nurses’ Health Study and the Health Professionals Follow-up Study. Researchers followed tens of thousands of men and women to identify aspects of their diets and lifestyles—such as regular tea drinking—that were associated with lower risk for disease.

• Cardiovascular health: The Harvard studies have found that people who drank tea regularly were at lower risk for heart disease. Antioxidants in tea may prevent damage to artery walls associated with chronic all-body inflammation. Substances in tea may also help to lower blood pressure or improve cholesterol. A study in Japan found that people who drank the green tea once or twice daily were 20 percent less likely to have strokes and heart attacks than those who drank tea seldomly.
• Diabetes prevention: Tea drinking is also linked to a reduced risk of diabetes. When the body’s ability to control blood sugar goes haywire, it leads to dangerously high blood glucose and a host of serious harms to your health. The polyphenols in tea may sensitize cells to insulin, which helps the body control blood sugar swings after you eat.