From green tea to hibiscus, from white tea to chamomile, teas are chock full of flavonoids and other healthy goodies.

Regarded for thousands of years in the East as a key to good health, happiness, and wisdom, tea has caught the attention of researchers in the West, who are discovering the many health benefits of different types of teas.

Studies have found that some teas may help with cancer, heart disease, and diabetes; encourage weight loss; lower cholesterol; and bring about mental alertness. Tea also appears to have antimicrobial qualities.

“There doesn’t seem to be a downside to tea,” says American Dietetic Association spokeswoman Katherine Tallmadge, MA, RD, LD. “I think it’s a great alternative to coffee drinking. First, tea has less caffeine. It’s pretty well established that the compounds in tea – their flavonoids – are good for the heart and may reduce cancer.”

Although a lot of questions remain about how long tea needs to be steeped for the most benefit, and how much you need to drink, nutritionists agree any tea is good tea. Still, they prefer brewed teas over bottled to avoid the extra calories and sweeteners.

Here's a primer to get you started.

Health Benefits of Tea: Green, Black, and White Tea

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, known as ECGC, may help against free radicals that can contribute to cancer, heart disease, and clogged arteries.

All these teas also have caffeine and theanine, which affect the brain and seem to heighten mental alertness.

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.

Here's what some studies have found about the potential health benefits of tea:

Green 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.
Black tea: 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.
White tea: Uncured and unfermented. One study showed that white tea has the most potent anticancer properties compared to more processed teas.
Oolong tea: 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.
Pu-erh tea: 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.

Health Benefits of Tea: Herbal Teas

Made from herbs, fruits, seeds, or roots steeped in hot water, herbal teas have lower concentrations of antioxidants than green, white, black, and oolong teas. Their chemical compositions vary widely depending on the plant used.

Varieties include ginger, ginkgo biloba, ginseng, hibiscus, jasmine, rosehip, mint, rooibos (red tea), chamomile, and echinacea.

Limited research has been done on the health benefits of herbal teas, but claims that they help to shed pounds, stave off colds, and bring on restful sleep are largely unsupported.

Here are some findings:

Chamomile tea: Its antioxidants may help prevent complications from diabetes, like loss of vision and nerve and kidney damage, and stunt the growth of cancer cells.
Echinacea: Often touted as a way to fight the common cold, the research on echinacea has been inconclusive.
Hibiscus: A small study found that drinking three cups of hibiscus tea daily lowered blood pressure in people with modestly elevated levels.
Rooibos (red tea): A South African herb that is fermented. Although it has flavonoids with cancer-fighting properties, medical studies have been limited.

Health Benefits of Tea: Instant teas

Instant tea may contain very little amounts of actual tea and plenty of sugars or artificial sweeteners. For health’s sake, check out the ingredients on the label.

Can Tea Be Bad for Your Health?

Most teas are benign, but the FDA has issued warnings about so-called dieter’s teas that contain senna, aloe, buckthorn, and other plant-derived laxatives.

The agency also warns consumers to be wary of herb-containing supplements that claim to kill pain and fight cancer. None of the claims is backed by science and some of the herbs have led to bowel problems, liver and kidney damage, and even death.

The FDA cautions against taking supplements that include:

Comfrey
Ephedra
Willow bark
Germander
Lobelia
Chaparral
These cautions aside, nutritionists say to drink up and enjoy the health benefits of tea.

“You want to incorporate healthy beverages in your diet on a more regular basis to benefit from these health-promoting properties," says Diane L. McKay, PhD, a Tufts University scientist who studies antioxidants. "It’s not just about the foods; it’s about what you drink, as well, that can contribute to your health."

By Julie Edgar
WebMD Feature 
Reviewed by Louise Chang, MD
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http://www.webmd.com/diet/features/tea-types-and-their-health-benefits