While artisanal sourdough is known in baking circles as the healthier choice, and there’s even some evidence to suggest that people with coeliac disease can tolerate the long-fermented bread, another study has shown study finds sourdough may not be the best choice for everyone’s gut.

A recent study carried out at the Weizmann Institute of Science in Israel looked into the way the digestive system reacts when fed certain types of food, and how those reactions are linked to our gut microbiome. Microbiome is our gut flora, which is made up of trillions of bacteria living mainly in our large bowel. Everyone has a slightly different makeup of bacteria depending on things such as diet, medication and genetics study finds sourdough not best for choice for everyone.

Researchers at the Weizmann Institute were interested to know how the digestive system would respond to slow-fermented, artisanal bread as opposed to plain white bread. Test subjects were divided into two groups. For one week, one group ate industrial white bread made from mostly refined wheat flour from a major brand in Israel. Then, after a two-week break, they were given a sourdough-leavened bread made from wholegrain wheat flour and prepared with “traditional methods” in an artisanal bakery. The second group conducted the experiment the other way around.

“We were sure that the sourdough bread would come out a healthier choice but, much to our surprise, we found no difference between the health effects of the two types of bread,” Professor Eran Segal told Israeli newspaper Haaretz.

Haaretz reported, “The findings were quite varied, individual and unexpected. For example, the blood sugar levels of one participant who ate the sourdough bread rose significantly, but returned to normal after a few hours. But ingesting white bread caused his blood sugar to rise only moderately and return to normal levels much more quickly. In other participants the effect was just the opposite.”

Overall, the study concluded that the reaction to each type of bread was “person specific”, and researchers found they could actually predict which type of bread would be better for a subject by analysing their gut microbiome.

The clinical report concluded, “…our study underlines the importance of personalisation in dietary recommendations”, and said their comparison of “healthy” and “unhealthy” breads suggested “universal dietary recommendations may have limited efficacy”.