Health Benefits of Green Tea (part 3)
It’s difficult not to gush about green tea.
More than a decade’s worth of research about green tea’s health benefits — particularly its potential to fight cancer and heart disease — has been more than intriguing, as have limited studies about green tea’s role in lowering cholesterol, burning fat, preventing diabetes and stroke, and staving off dementia.
“I believe in green tea based on everything written about it,” says Katherine Tallmadge, RD, LD, a nutritionist and spokeswoman for the American Dietetic Association. “Green tea, white tea, black tea — I like all of them.”
Still, real-world evidence is lacking; most of the consistent findings about green tea’s health benefits have come out of the lab.
The few large-scale human studies that have focused on green tea’s impact on heart disease and cancer are promising, but many of those were conducted in the East, where green tea is a dietary mainstay. The outcomes are likely influenced by other lifestyle factors such as high consumption of fish and soy protein, says cardiologist Nieca Goldberg, MD, a spokeswoman for the American Heart Association and medical director of the New York University Women’s Heart Center.
But Goldberg agrees with other health professionals: green tea has important antioxidants and compounds that help in maintaining good health.
Green Tea’s Powerful Antioxidants
Green tea’s antioxidants, called catechins, scavenge for free radicals that can damage DNA and contribute to cancer, blood clots, and atherosclerosis. Grapes and berries, red wine, and dark chocolate also have potent antioxidants.
Because of green tea’s minimal processing — its leaves are withered and steamed, not fermented like black and oolong teas — green tea’s unique catechins, especially epigallocatechin-3-gallate (EGCG), are more concentrated.
But there’s still a question of how much green tea you need to drink to reap its health benefits. EGCG is not readily “available” to the body; in other words, EGCG is not always fully used by the body.
“We must overcome the issue of poor bioavailability [and other issues] in order to get the most out of their benefits,” says Tak-Hang Chan, PhD, professor emeritus in the department of chemistry at McGill University in Montreal. Chan has studied the use of a synthetic form of EGCG in shrinking prostate cancer tumors in mice, with success.
Green Tea vs. Cancer
Marji McCullough, ScD, RD, the American Cancer Society’s strategic director of nutritional epidemiology, says human studies haven’t yet proven what researchers like Chan have discovered in the lab: green tea’s EGCG regulates and inhibits cancer growth and kills cells that are growing inappropriately.
“Epidemiologically, one of the challenges is finding populations that drink enough green tea and have for a long time,” she says. “With cancer, it’s always difficult to find the exposure time,” or the point at which cancer cells begin to develop.
Green Tea vs. Cancer continued…
Still, it’s difficult not to be intrigued by a few human studies that have shown that drinking at least two cups of green tea daily inhibits cancer growth.
One of them, a study conducted in Japan that involved nearly 500 Japanese women with Stage I and Stage II breast cancer, found that increased green tea consumption before and after surgery was associated with lower recurrence of the cancers.
Studies in China have shown that the more green tea that participants drank, the less the risk of developing stomach cancer, esophageal cancer, prostate cancer, pancreatic cancer, and colorectal cancer.
Finally, a recent analysis of 22 studies that probed the correlation between high tea consumption and reduced risk for lung cancer concluded that by increasing your daily intake of green (not black) tea by two cups may reduce the risk of developing lung cancer by 18%.