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Sara Baker says the light went on in her head after a cup of hot cocoa set off a storm in her stomach.

“I went back and looked at the package, and there it was: carrageenan,” said Baker, a career services coordinator from Bloomington, in central Illinois.

Baker had been taking medication for ulcerative colitis for years but still suffered debilitating digestive flare-ups without warning. She had read warnings about carrageenan in a natural health newsletter but didn’t take them seriously. After all, researchers haven’t conclusively linked the common food additive to gastrointestinal problems in humans.

This time, though, “it really clicked,” she said. “It took awhile to learn just how many things it’s in, but now that know, I can avoid it, and I no longer have the problems.”

Experiences like Baker’s have led some people with gastrointestinal problems to sidestep mainstream medical advice and avoid carrageenan, a seaweed-derived texturizer found in meat, dairy and other processed foods – including some organic products.

For scientists, however, these are just anecdotes. Though studies on lab animals and human cells have suggested that carrageenan can cause gastrointestinal inflammation, many researchers and physicians say it’s unclear whether the additive has the same impact on people who consume it.

Scientists at the University of Illinois at Chicago and University of Chicago are seeking to address that question with a controlled clinical trial that Baker is participating in.

“I believe it’s worth investigating and doing the science to find out,” said Dr. Stephen Hanauer, a medical professor and chief of gastroenterology and nutrition at University of Chicago Medicine.

His co-researcher, UIC physician and professor Joanne Tobacman, has been looking at the health effects of carrageenan for more than a decade and is concerned enough to have petitioned the U.S. Food and Drug Administration in 2008 to prohibit the use of carrageenan in food.