This is Scientific American's 60-second Science, I'm Christopher Intagliata.
A lot of restaurant menus these days have gluten-free options. Problem is, many of the dishes may not be gluten-free at all.
"About a third overall, 32 percent, of gluten-free-labeled restaurant foods had a gluten-found result." Benjamin Lebwohl, a gastroenterologist and epidemiologist at Columbia University.
His team got that 1/3 number by crowdsourcing data from 804 restaurant patrons, who used handheld gluten-testing devices to scan more than 5,600 restaurant food samples from across the U.S.
The devices can detect gluten at slightly lower levels than the maximum concentration the FDA allows for packaged foods—20 parts per million. So there could be some harmless false positives in the data.
But we suspect given that large proportion that this is clearly a bigger problem than in packaged food, where probably less than two percent of all packaged food has detectable gluten of greater than 20 parts per million.
The results are in The American Journal of Gastroenterology.
For those who need to avoid gluten for health reasons, Lebwohl has a few tips. "Food that was tested around dinnertime was more likely to have gluten than food earlier in the day." And avoid allegedly gluten-free pizzas and pastas, he says, which scored more violations than other dishes. More than half of all pizza and pasta dishes tested positive for gluten.
So a salad, for lunch, might be a safer bet.
Thanks for listening for Scientific American — 60-Second Science. I'm Christopher Intagliata.