University of Illinois scientists say they have discovered one of the secrets to soy’s health benefits: Genistein — a bioactive component in soy foods — protects against colon cancer by repressing a signal that leads to abnormal, uncontrolled growth of cells, polyps, and malignant tumors.
In a new study published online in the journal Carcinogenesis, medical investigators found that long-term exposure to genistein reduced the number of pre-cancerous lesions in the colons of laboratory rats exposed to a carcinogen by 40 percent.
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Hong Chen, a university professor of food science and human nutrition who led the study, said researchers determined the soy compound changes the genetic activity of three genes involved in cell growth.
"In 90 percent of colon cancer patients, an important growth-promoting signal is always on, leading to uncontrolled growth and malignancies," Chen said. "Our study suggests that the aberrant … signaling during the development of colon cancer can be regulated by soy-rich diets."
For the study, the scientists fed pregnant rats and their offspring a diet containing genistein, then exposed them to a carcinogen. After nearly two months, the researchers checked the animals’ colons and compared them to those of rats who had not been exposed to the cancer-causing substance to see if the soy-rich diet offered any protective effect against cancer.
The result showed virtually no differences in both groups of animals.
"Genistein decreased the expression of three genes and repressed this signaling process that is associated with abnormal cell growth and cancer development," Chen said.
She added that colon cancer is an epigenetic disease, meaning dietary and environmental factors can influence genes to be switched on or off. Past research has shown immigrants from Asia — where soy is traditionally a food staple — experience rising levels of colon cancer as they adopt the eating habits of the Western nations, she added.
"The genetic information you inherit from your parents is not the whole story. Our dietary choices, our exposure to environmental toxins, even our stress levels, affect the expression of those genes," she said.
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