Tea is a name given to a lot of brews, but purists consider only green tea, black tea, white tea, oolong tea, and pu-erh tea the real thing. They are all derived from the Camellia sinensis plant, a shrub native to China and India, and contain unique antioxidants called flavonoids. The most potent of these may help against free radicals that can contribute to cancer, heart disease, and clogged arteries. In clinical research over the early 21st century, tea has been studied extensively for its potential to lower the risk of human diseases.
Drinking caffeinated tea may improve mental alertness. There is preliminary evidence that the caffeine from long-term tea (or coffee) consumption provides a small amount of protection against the progression of dementia or Alzheimer’s disease during aging, although the results across numerous studies were inconsistent.
Green tea is commonly believed to be a weight loss aid. Use of green tea for attempted weight loss carries a small risk of adverse effects, such as nausea, constipation, and stomach discomfort.
Here’s what some studies have found about the potential health benefits of tea:
Made with steamed tea leaves, it has a high concentration of EGCG and has been widely studied. Green tea’s antioxidants may interfere with the growth of bladder, breast, lung, stomach, pancreatic, and colorectal cancers; prevent clogging of the arteries, burn fat, counteract oxidative stress on the brain, reduce risk of neurological disorders like Alzheimer’s and Parkinson’s diseases, reduce risk of stroke, and improve cholesterol levels.
Made with fermented tea leaves, black tea has the highest caffeine content and forms the basis for flavored teas like chai, along with some instant teas. Studies have shown that black tea may protect lungs from damage caused by exposure to cigarette smoke. It also may reduce the risk of stroke.
Uncured and unfermented. One study showed that white tea has the most potent anticancer properties compared to more processed teas.
In an animal study, those given antioxidants from oolong tea were found to have lower bad cholesterol levels. One variety of oolong, Wuyi, is heavily marketed as a weight loss supplement, but science hasn’t backed the claims.
Made from fermented and aged leaves. Considered a black tea, its leaves are pressed into cakes. One animal study showed that animals given pu-erh had less weight gain and reduced LDL cholesterol.
The more processed the tea leaves, usually the less polyphenol content. Polyphenols include flavonoids. Oolong and black teas are oxidized or fermented, so they have lower concentrations of polyphenols than green tea, but their antioxidizing power is still high.