Phenylthiocarbamide (PTC) is not found in nature, but the ability to taste it correlates strongly with the ability to taste other bitter substances that occur naturally, especially toxins. Eons ago, the ability to discern bitter tastes developed as an evolutionary mechanism to protect early humans from eating poisonous plants.
"We found evidence at the molecular level that natural selection has maintained the variation in the gene that allows us to taste or not taste PTC," said geneticist Stephen Wooding, Ph.D., corresponding author on the study and a post-doctoral fellow at the Eccles Institute of Human Genetics at the University of Utah School of Medicine.
Today, the ability to taste, or not taste, the compound influences what people eat and even whether they smoke cigarettes.
People who can taste PTC are less likely to eat cruciferous vegetables such as broccoli, according to Wooding, which could be a problem because these vegetables contain important nutrients. If the ability to discern bitter tastes discourages PTC tasters from eating broccoli, it also may have the advantage of dissuading them from inhaling the acrid smoke of cigarettes. "Among smokers, there seems to be an excess of PTC non-tasters," Wooding said. "So it seems that PTC tasters are less likely to smoke."
The researchers recently published their findings in the American Journal of Human Genetics.
Typically, over hundreds of thousands years, genetic drift takes place, a process in which gene frequencies and genetic traits change randomly within a population. Under that expectation, everybody either would be a PTC taster or non-taster by now. But worldwide the ratio has remained at roughly
Contact: Stephen Wooding
University of Utah Health Sciences Center