Sunday, November 22, 2009

Polyphenols and flavonoids

The ancient Chinese considered tea medicine. Ancient Chinese proverbs describe tea ‘as a miraculous way to prolong life.’ Today science is confirming much of what Chinese folklore has known for millennia. Studies all over the world have reported that tea, especially green and oolong tea, reduces the risk of cardiovascular disease, lowers bad cholesterol levels, prevents many of the cancers common in the modern era, lowers blood sugar levels, raises metabolism reducing body fat, and prevents tooth decay and bad breath.
Tea, especially green and oolong tea, contains large amounts of polyphenol, a naturally occurring antioxidant compound. Antioxidants work to neutralize free radicals, which are implicated in a host of chronic illnesses, including cancer and heart disease. Studies indicate that the polyphenol found in green and oolong teas have an antioxidant effect more powerful than vitamin E. Polyphenols are also known to keep the influenza virus in check.
Tea naturally contains the minerals fluoride and manganese, as well as vitamins C, B2, D and K and a number of amino acids. Clearly, tea is one of those earthly wonders, delicious and good for one’s health.
Health Benefits of Tea: Green, Black, and White Tea
From Web MD

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.
Can Tea Be Bad for Your Health?
from Web MD

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:
Willow bark
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."

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