The presence of a fern, Pteridium spp., in the Venezuelan Andes may be responsible for the high incidence of gastric cancer in the area, according to a study recently published in the International Journal of Cancer.
Gastric cancer is characterized by the presence of cancer cells in the tissues of the stomach, which is located in the upper abdomen. Stomach cancer is currently the second leading cause of cancer death worldwide. Inhabitants of the Venezuelan Andes have an unusually high incidence of gastric cancer, which has led researchers to explore any environmental factors that may be involved.
Both genetic and environmental risk factors can contribute to the development of cancer. Often when a certain type of cancer is prevalent in one region, researchers will search for environmental factors that could be associated with the cancer. Environmental factors could include diet, exercise, pollution, stress or other more specific factors unique to a region. Researchers continue to work toward determining factors that may contribute to the development of different types of cancer so that better strategies for prevention and/or screening can be produced and implemented.
Researchers performed an epidemiological study in Merida, Venezuela and found a correlation between the high incidence of gastric cancer and the presence of a fern, Pteridium spp. The fern contains a toxic compound called ptaquiloside and was already known to be toxic to humans.
In this study, the researchers found ptaquiloside in milk from the local cattle. The cattle grazed in pastures where the fern was prevalent. The researchers observed that the risk of developing gastric cancer was 3.6 times higher in the highlands, where the fern is prevalent, than in the adjacent control state of Zulia.
The farmers in this region are small producers of dairy cattle and the milk is usually consumed locally. Pasteurizing or boiling the milk does not affect the ptaquiloside content; therefore the only way to work toward preventing the high incidence of gastric cancer in the region is to eliminate the fern.
This is the first study to suggest that milk is the vehicle for passing along the ptaquiloside carcinogen. Now, researchers are using this information to search for ptaquiloside in other dairy products such as yogurt and cheese, which are distributed over larger areas. As researchers continue to identify the environmental risk factors that contribute to certain types of cancer, they increase the chances of preventing these cancers from developing and provide individuals with opportunities to prevent cancer through changes in lifestyle. ( International Journal of Cancer, Vol 91, pp. 252-259, 2001)