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An additive found in baked goods and processed meats could disrupt the endocrine system, according to researchers. Getty Images

Maybe it’s not how much you eat, but something that’s added to what you eat that’s making you gain weight.

Researchers have found that a common food additive increases levels of hormones associated with an increased risk of both obesity and diabetes.

“Understanding how ingredients in food affect the body’s metabolism at the molecular and cellular level could help us develop simple but effective measures to tackle the dual epidemics of obesity and diabetes,” Gökhan S. Hotamışlıgil, a study author and a professor of genetics and metabolism and director of the Sabri Ülker Center for Metabolic Research at Harvard T. H. Chan School, said in a statement.

The recent study finds one food additive may be (at least partly) responsible for many health issues.

The food additive is propionate, a naturally occurring fatty acid used to keep foods fresh and prevent mold. Some foods containing propionate include:

  • bread and baked goods
  • dairy products, including flavored milk, cheeses, and puddings
  • processed meats such as canned fish and sausage casings

Other foods with propionate added to them include beer, sports drinks, diet foods, commercially prepared potato salad, nut butters, and vinegar.

Researchers initially tested propionate in mice and found it quickly activated the sympathetic nervous system, the part responsible for automatic functions such as heart rate.

This caused a surge in hormones that increased blood sugar levels in the test animals, a characteristic symptom of diabetes. When the mice were chronically exposed to the same amount of propionate typically consumed by humans, they gained weight and became insulin resistant (prediabetes).

The findings suggest propionate is an endocrine disruptor.

“Endocrine disruptors are chemicals that are usually produced for commercial purposes that accidentally interfere with the normal function of hormones. This can contribute to a wide array of health conditions because hormones play such important roles in the human body,” Dr. Mansur E. Shomali, an endocrinologist at MedStar Union Memorial Hospital in Baltimore, told Healthline.

To discover how these findings applied to humans, the researchers designed a double-blind, placebo controlled study with 14 participants.

Half of the participants took one gram of propionate in their food. The other half ingested a placebo.

Those who ate food with propionate experienced the same surge in hormones as the mice. According to the researchers, this indicates that propionate may be an endocrine disruptor that increases the risk of both diabetes and obesity in humans.

“Obesity and diabetes are complicated conditions that are due to genetic, environmental, and behavioral factors,” Shomali said. “The incidence of obesity and diabetes has grown dramatically over the past two decades. Since the human gene pool has not changed during that time, researchers are looking for environmental factors.”

However, some medical professionals are hesitant to accept the study results, at least for now.

“It’s such a small sample size that you can’t really draw any meaningful conclusions,” Dr. Charles Dinerstein, MBA, FACS, a senior medical fellow at the American Council on Science and Health, told Healthline.

Bisphenol-A (BPA), an endocrine-disrupting chemical found in plastics and food packaging, has already been banned from baby bottles and sippy cups, according to Shomali.

He said the U.S. Environmental Protection Agency (EPA) is conducting screening tests on many chemicals. The results are available at the website.

Work has been ongoing for decades to protect the public from endocrine-disrupting chemicals.

According to the National Institute of Environmental Health Sciences, a drug called diethylstilbestrol (DES), which was used to treat women with high-risk pregnancies until it was banned in the 1970s, was linked to a rare form of vaginal cancer.

Like propionate, animal research has also confirmed a link to high blood sugar and obesity.

Studies in mice demonstrated that exposure to the endocrine-disruptor chemical DES in young people can result in obesity and high blood-sugar levels as adults,” Shomali said.

He explained that the exact mechanism isn’t completely understood, but “it may have to do with changes in the part of the brain that regulates hunger, eating behavior, and metabolism.”

The United States approved an amendment to the Food, Drug, and Cosmetic Act in 1958 that prohibited the Food and Drug Administration (FDA) from approving food additives that had been linked to cancer.

But there was a loophole.

Additives used before the amendment was passed were “grandfathered” in and are still used in the United States.

Shomali said other nations, particularly in Europe, are trying to address endocrine-disruptor risks.

“It’s difficult to say that the U.S. is lagging behind. Most countries are struggling with their rules since strong evidence of the risks is often lacking,” he said. “In Europe, certain pesticides and other compounds are restricted or banned. Some compounds are banned by the European agency. Others are banned by individual countries.”

Dinerstein urged caution while analyzing the results.

“The science done on mice was thought out and done well,” he said. “Propionate likely does alter human metabolism, but it’s not a disruptor. It’s like anything else we ingest: It just changes our metabolic profile.”