Study Provides Additional Evidence for the Effectiveness of Green Tea in Preventing Colon Cancer

FREDERICK, MD - April 11, 2017

Promising new research suggests that consuming green tea can significantly decrease the risk of developing colon cancer, one of the most common types of cancer in the United States.

Portrait of Xingpei Hao

Xingpei Hao, M.D., Ph.D.

Although overall colorectal cancer rates have been declining for several decades, incidence is increasing among young adults. Rates are also increasing in developing countries where people are adopting Western-style diets.

A team of investigators from both Rutgers University’s Susan Lehman Cullman Laboratory for Cancer Research and the Frederick National Lab recently published a study in Nutrition and Cancer that suggested consuming green tea polyphenols can significantly lower the risk of developing malignant tumors. Polyphenols are a type of antioxidant substance that can protect cells from being damaged. Research has shown that increased consumption of plant-based foods and beverages, such as green tea, may be an effective way to prevent cancer.

“Changing dietary components may provide an efficacious mean to regulate the course of carcinogenesis, which usually takes more than 10 to 20 years. Secondary to water, tea is the most commonly consumed beverage in the world,” explained Xingpei Hao, M.D., Ph.D., a lead author on the paper and former employee in the Frederick National Lab’s Pathology and Histotechnology Laboratory.

The work, conducted in rats, follows previous studies that demonstrated polyphenon E (PPE), a standardized green tea polyphenol mixture, prevented the formation of tube-like structures on the surface of the colon after just eight weeks. These structures, called aberrant crypt foci (ACF), precede the formation of polyps and are one of the earliest changes seen in the colon that may lead to cancer.

This latest study further demonstrated the effectiveness of PPE by using the same animal research models, which resemble human colorectal cancer development, but in a longer-term experiment that looked beyond ACF formation and characterized the molecular changes with colorectal tumors.

The rats were treated with azoxymethane, a carcinogenic chemical compound, and then fed a 20% high-fat diet with or without PPE for 34 weeks. The PPE dosage was selected based on previous studies by the research team, which showed that 0.24% PPE in the diet significantly impeded colon ACF growth. This is the equivalent of consuming about 4–5 cups of tea each day for humans.

Following the 34 weeks of dietary treatment with PPE, 83% of the control rats and 68% of PPE-treated rats developed visible tumors. PPE was also shown to reduce tumor size by 45% and multiplicity of the tumors by 55%.

Scientific image showing before and after exposure to green tea, demonstrating its protective effect.

The brown-stained cells are beta-catenin, an adhesion molecule that can prevent mutations leading to cancer. The left image shows beta-catenin alongside cancerous cells. The right image shows beta-catenin after exposure to green tea.

The research findings supported the scientists’ notion that “oncogenic signaling at the molecular level is a major target of PPE, and its inhibition by PPE treatment might be critical for the overall inhibition of colorectal tumorigenesis,” as the authors wrote in their Nutrition and Cancer article.

The investigators also found that PPE promoted enhanced natural cell death and anti-inflammatory activity. Connections between inflammation and colon cancer have been well-documented by Hao’s previous work, and inflammatory bowel disease is an important risk factor for the development of colon cancer.

“These events may be used as biomarkers to monitor the effects of tea polyphenols on humans,” said Hao. “These studies provide the basis for clinical trials in human colon cancer prevention.”

In addition to Dr. Hao, the research team included scientists from Rutgers University, the University of Massachusetts, Penn State University, and Chungbuk National University, Cheongju, Chungbuk, Korea.

By Max Cole; images courtesy of Xingpei Hao

Last updated: April 11, 2017