This is

is Scientific American 60 Second Science.

I'm Christopher Intagata.

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% of gluten-free-labeled restaurant foods had a gluten-found result.

Benjamin Leibweil, a gastrointestinalologist and epidemiologist at Columbia University.

His team got that one-third number by crowdsourcing data from 804 restaurant patrons,

who used hand-held gluten-testing devices to scan more than 5,600

restaurant food samples from across the US. 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 2% of all packaged food has detectable gluten of greater than 20

parts per million. The results are in the American Journal of Gastroenterology.

And for those who need to avoid gluten for health reasons,

Leibwell has these tips.

Food that was tested around dinner time

was more likely to have gluten detected than food earlier in the day.

And avoid allegedly gluten-free pizzas and pastas, he says, which scored more violations than other dishes.

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