The level of fat and cholesterol was also tested and the kidney, liver enzymes and the inflammation and damage caused to tissue.
"The initial finding, and this was very much contrary to our expectation, was that there were no clinically significant differences between the effects of these two types of bread on any of the parameters that we measured", said Eran Segal, a computational biologist at the Weizmann Institute of Science and one of the study's senior authors.
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.
In the study, 20 healthy participants ate bread regularly - it made up a quarter of their daily calorie intake. After a two-week break, they switched, and for a week the group that had previously eaten white bread ate the sourdough bread, and vice versa. There were no significant overall differences based exclusively on the bread and glycemic response.
She said: "Researchers were expecting to see differences in the rise in blood sugar after the participants consumed the white bread versus the wholegrain sourdough bread and they also looked to see if subjects' gut flora changed".
Ditto for bread: While you might favour dark rye thinking it'll do you good, you personally might be better off with a sponge-like $1 loaf of white bread.
The study showed, for example, that about half of the participants had higher blood sugar levels after eating white bread, whereas the other half had higher blood sugar after eating sourdough bread. But when researchers examined each person individually, a different pattern emerged. "To date, the nutritional values assigned to food have been based on minimal science, and one-size-fits-all diets have failed miserably", says Eran Elinav, a researcher in the Department of Immunology at the Weizmann Institute. Some of them exhibited a higher glycemic response, but it contained people from both groups, depending on the type of bread they were more sensitive to. "These findings could lead to a more rational approach for telling people which foods are a better fit for them, based on their microbiomes", stated Segal.
Everyone has a different health profile that may be influenced by several factors, such as genetics and family history.
Some people may prefer brown bread while others favour white - but there has been little dispute that wholemeal is healthier.
Bread occupies a unique place in our diet: it accounts for about one-tenth of the calories many people in the West consume and up to 40% of the caloric consumption in some non-Western countries - more than any other food product. However, on taking a further look at the results, the team found that there were differences in the way individuals responded to the different breads.