Many animal studies have suggested that chemicals added to breakfast cereals and other common products are adding to America's obesity crisis, but showing exactly how the process happens in humans has been difficult. Scientists at Cedars-Sinai have solved the problem.

The researchers tested three chemicals that are common in modern life. Butylhydroxytoluene (BHT) is an antioxidant commonly added to breakfast cereals and other foods to protect nutrients and keep fats from turning rancid; perfluorooctanoic acid (PFOA) is a polymer found in some cookware, carpeting and other products; and tributyltin (TBT) is a compound in paints that can make its way into water and accumulate in seafood.

The investigators used hormone-producing tissues grown from human stem cells to demonstrate how chronic exposure to these chemicals can interfere with signals sent from the digestive system to the brain that let people know when they are "full" during meals. When this signaling system fails, people may continue to eat, thus gaining weight.

"We discovered that each of these chemicals damaged hormones that communicate between the gut and the brain," said Dhruv Sareen, Ph.D. When the three chemicals were tested together, the result was even more pronounced.  

Of the three chemicals tested, BHT produced some of the strongest detrimental effects, Sareen said. BHT (butylated hydroxytoluene) is a chemical allowed to be used as a food additive to prevent oxidation.

BHT is on the Food and Drug Administration's GRAS — generally recognized as safe — list. It is used in foods, such as cereals — although some food manufacturers have eliminated it from their products — and is also used in cosmetics and pharmaceuticals. Some studies, however, have indicated that in addition to weight gain, BHT also increases the risk of cancer, and can cause liver enlargement.

Sareem said that while other researchers have shown the compounds can disrupt hormone systems in laboratory animals, the new study is the first to use human pluripotent stem cells and tissues to show how they may disrupt hormones that are critical to preventing obesity in people.

Sareem's research found that the chemical damage occurred in early-stage "young" cells, suggesting that the findings may indicate that a defective hormone signaling system could perhaps impact a pregnant mother as well as her fetus in the womb.

More than 80,000 chemicals are approved in the United State for use in everyday items such as foods, personal care products, household cleaners and lawn-care products, according to the National Toxicology Program of the U.S. Department of Health and Human Services. While the program states on its website that relatively few chemicals are thought to pose a significant risk to human health, it also states: "We do not know the effects of many of these chemicals on our health."

It has been difficult to test these chemicals on humans because of the health risks of exposing human subjects to possibly harmful substances, so many widely used compounds remain unevaluated in humans for their health effects, especially to the hormone system.

"By testing these chemicals on actual human tissues in the lab, we potentially could make these evaluations easier to conduct and more cost-effective," Sareen said.

Earlier studies have suggested that BHT increases the risk of cancer, and can cause liver enlargement.