There may be a barrage of studies hailing whole wheat bread as the healthiest choice, but new findings suggest that it isn’t necessarily the smarter option for everybody.

The study, which compared how artisanal whole wheat sourdough bread performed against processed white bread in the bodies of 20 healthy individuals, pored over how differently people react to enhanced intake of both bread types.

Brown Isn’t Readily Better

"The findings for this study are not only fascinating but potentially very important, because they point toward a new paradigm: different people react differently, even to the same foods," said Weizmann Institute researcher and senior author Eran Elinav in a statement.

"To date, the nutritional values assigned to food have been based on minimal science, and one-size-fits-all diets have failed miserably,” Elinav added, noting that their findings could help people better rely on their microbiomes and bodies in choosing the right food to eat.

For one week, half of the study participants took an increased amount of processed and packaged white bread to form a quarter of their calorie intake. The remaining half did the same for whole wheat sourdough.

After two weeks without taking bread, the diets of the two groups were switched.

Before and during the experiment, the team tracked the subjects’ fat, glucose, and cholesterol levels, as well as tested their minerals, iron, calcium, and magnesium status. They also monitored kidney and liver enzymes, along with different inflammation and tissue damage markers.

Also checked was the subjects’ microbiomes before, during, and after the research.

According to computational biologist and senior author Eran Segal, the initial results went against their expectations: they found no “clinically significant” variations between the two breads’ effects on any of their measured parameters.

But upon looking at the subjects’ glycemic responses, the team saw that around half better responded to white bread, while another half better responded to whole wheat bread. It affirmed earlier work noting that people maintain varying glycemic responses to the same diet.

Differences In Gut Microbiome May Be Key

The researchers guessed that differences in people’s microbiomes, or the bacteria naturally living in the intestines, may account for the different responses to different types of bread.

More research, however, may be necessary to exactly understand how different kinds of bread and food affect different individuals.

Dietitian Rosie Schwartz, for instance, warned that not all whole grain varieties are created equal, which should have prompted the team to broaden their study’s scope.

She explained that there could have been different results if the researchers looked at rye, barley, and oats for example, all of which containing soluble fiber and could change what happens with glycemic response. Apart from blood sugar, whole grain intake also affects cancer risk, she added.

Another nutritionist, Samantha Heller from NYU Langone Medical Center, told CBS News that whole grain breads, cereals, crackers, and brown rice have all been previously shown to slash the risk of heart disease, type 2 diabetes, inflammation, certain cancer types, and obesity.

Coauthor Avraham Levy highlighted another limitation of their study, namely people would eat less whole wheat bread in general due to its high-fiber content.

“We didn’t take into consideration how much you would eat based on how full you felt,” he said.

Both study senior authors reported that they serve as paid consultants for a firm offering personalized dietary advice based on gut microbiome.

The findings were detailed in the journal Cell Metabolism.