Tea As A Protector Of Our Health?

Green tea is a likely choice these days for people looking for health benefits from their beverages. But new research indicates that all tea is good for you, as long as it comes from the leaf of Camellia sinenis—as do all green, black, and red teas.

Here's some background on tea. Whether it turns out to be black, oolong, or green depends on the processing. To make green tea, the leaves are steamed, rolled, and dried. This keeps them from oxidizing, because it inactivates certain chemicals in the leaves. Red (oolong) and black teas are partially dried, crushed, kept in a temperature- and humidity-controlled environment to produce fermentation, and then fully dried. To "ferment" in this context means "oxidize," or blacken; this takes place as chemicals in the leaves react to heat. The difference between black and red teas is that black teas are fermented longer. Hence the distinctive tastes and chemical properties of each kind of tea.

The chemicals that make tea a potential protector of health are called polyphenols; these may have anti-cancer effects as well as heart benefits. Though green tea was once thought to have the most polyphenols, it turns out that black tea has a similar amount. The polyphenols in both green and black teas have antioxidant activity—that is, they help deactivate cell-damaging free radicals. Indeed, one study found that tea leaves have more antioxidant power by one measure than kale or strawberries, on a dry-weight basis (the study didn't compare common serving sizes). The evidence that tea protects against heart disease is not as strong. In some lab studies, researchers have found that polyphenols help prevent blood clotting and lower cholesterol levels.

The polyphenols in tea seem to operate in a variety of ways: for example, halting the damage that free radicals do to cells, neutralizing enzymes essential for tumor growth, and deactivating cancer promoters. One study of 35,000 postmenopausal women found that consuming at least two cups of tea daily cut the risk of digestive and urinary tract cancers. It is possible that tea protects against cancer only in people who (a) drink huge amounts of it and (b) are at high risk for cancer because they have a poor diet.

Thus, while tea may have health benefits, it clearly will not work miracles. Stomach cancer, for example, remains a major killer in China and Japan, where the highest amounts of green tea are consumed. But the evidence keeps mounting that tea has health benefits. Think of it as a back-up to a healthy diet and an adjunct to regular exercise and other good health habits—not as a miraculous potion that will keep you well by itself.