The small intestine can also sense 'sour' toxins in food, and expel such items almost immediately.
The study claims that bitterness also slows the digestive process, keeping bad food in the stomach longer and increasing the chances that it will be expelled.
The defense system in the gut against dietary toxins also triggers the production of a hormone that makes people feel full, presumably to keep them from eating more of the toxic food.
Timothy Osborne, molecular biology and biochemistry professor and study senior author, claimed that the, performed with mice, and the results may also have implications in human.
"We have evolved mechanisms to combat the ingestion of toxins in our food. This provides a framework for an entirely new area of research on how our bodies respond to what is present in our diets," said Osborne.
Usually, mammals can detect bitter taste of toxins in food, particularly when they consume a lot of plant material, which tends to contain more bitter-tasting, potentially toxic ingredients than meat.
When somebody swallows the toxins, bitter-taste receptors in the gut sense them and trigger the production of a hormone called cholecystokinin that both suppresses appetite and slows the movement of food from the stomach to the small intestine.
It was also found that cholesterol regulates the activity of bitter-taste receptors in the intestine, and diets high in plant material and potential toxins naturally are low in cholesterol, compared to low-toxin, high-cholesterol, meat-based diets.
In small intestine cell cultures, low levels of cholesterol triggered a stronger receptor response, while high levels caused a weaker response.
The researchers saw the same response in mice that were given drugs to stop the production and absorption of cholesterol.
In fact, their receptors were not only more active, their small intestine cells produced two to three times the amount of the appetite-suppressing hormone in the presence of bitter food, compared to normal mice.
The scientist could utilise this knowledge to make medicines less bitter, which in turn would allow for increased palatability and quicker absorption.
The study has appeared in the latest issue of the Journal of Clinical Investigation.