Is it better to eat mass-produced whole grain bread or old fashioned white bread?

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Is it better to eat whole-grain sourdough bread made traditionally, or a slice of industrially mass-produced white bread?

The answer arrived at by a recent study might surprise you: Researchers looked at major metabolic markers, with most of them related to the risk of type 2 diabetes, and found no significant differences between people who ate the artisan sourdough and people who ate the factory-manufactured white bread, New Scientist reports.

"The really shocking result was that on everything that we looked at, we didn’t find any difference between the effects of the two breads," a co-author says, per the Guardian.

The white bread studied contained refined wheat flour, preservatives, and emulsifiers. Whether sourdough (which was fresh) or white (which was packaged), participants ate more bread (25% of their total calories compared to a normal 10%) than usual, per a press release.

The study looked at the gut microbiomes plus clinical measures including cholesterol, blood sugar, fat, and mineral levels in 20 participants prior to its start. The subjects were then randomly assigned to either eat the sourdough or the white bread for one week, then take a two-week break and switch breads.

Participants' gut microbiomes did not appear to be changed based on the bread they ate and researchers found no measurable differences when looking at most markers, but they did find that while half the group had a higher blood glucose response to the white bread, the other half had a higher response to the sourdough.

Based on subjects' microbiomes, researchers could actually predict which half a participant would fall under. "The 'one-size-fits-all' diets that are given to the population as a whole, without personalization, are probably not optimal for everyone," a co-author says, per CBS.

(This trick may help you eat more veggies.)

This article originally appeared on Newser: Mass-Produced or Artisan Bread? Results May Surprise