Dr. Jia Sheng Wang, department head for environmental health science, pulls tea from every nook in his office as he explains the protective effects of green tea polyphenols (GTP) against cancer. He pulls bags from his dorm-sized freezer, canisters from his desk drawers, boxes between books on the shelves, and, of course, he has tea in his cup.
Green tea has no toxic side effects, yet his research suggests it makes a big difference, is inexpensive and easy to administer. In 20 years of research and publishing more than 30 papers on his findings, Wang has set the standard for safe testing protocol and pioneered the use of biomarkers.
When he began his career in public health, most studies on nutrition factors and disease relied on surveys. Even daily tea drinkers are hard-pressed to accurately report how much GTP they consume; not all teas contain GTPs. Green tea, which is prepared by drying or roasting fresh tea leaves, is the protective kind. Black tea (called red tea in China) is fermented to bring out certain flavors, but the process depletes the plant’s antioxidants. Oolong tea is a blend of half fermented and half fresh leaves. Most Americans drink black tea.
Biomarkers can be tested to objectively detect an activity, such as smoking, or a characteristic, such as susceptibility to infection. For example, if someone smokes, Wang’s lab can detect nicotine in that person’s blood or urine or respiratory residue. The Georgia Cancer Coalition scholar and his team are wrapping up a five-year study using biomarkers to measure the extent of GTPs’ efficacy as a preventative agent against liver cancer.
Liver cancer is the third-leading cause of cancer deaths in the world. Though less common in the United States, liver cancer cases have doubled in the last 10 years, and cases are expected to double again over the course of the next decade. It is difficult to treat, so prevention is the best strategy. China accounts for 55 percent of liver cancer cases, many of them clustered in the southeast region. The geographic correlation hints at environmental factors brewing, just the type of work the College of Public Health is particularly suited for.
Wang’s team went to China and collaborated with Guangxi Cancer Institute, Fusui Liver Cancer Institute, Shanghai Cancer Institute, with grants from America’s National Cancer Institute and the National Institute of Environmental Health Science and the Chinese Natural Science Foundation. They screened 15,000 people for high risk factors and recruited 1,800 study participants to take a daily regimen of GTP capsules and check in for many physical exams over the years. One-third received capsules with half a gram, another third got a higher dose and the other third took placebos.
Amazingly, less than 10 percent of the participants dropped out after five years. By contrast, in the U.S., a retention rate of 50 percent would be considered successful.
“Everyone knows someone affected by liver cancer, so people really want to participate in finding out how to prevent it or learn why this is happening,” Wang said.
The placebo group has shown more than double the incidence of liver cancer compared to the GTP capsule groups. The dramatic results are not enough for Wang’s team. Their next study will be to find out why.
Posted March 8, 2012.
Originally published in the 2011 issue of the UGA College of Public Health Magazine.