They had their glucose, fat, minerals, and cholesterol levels measured at different times of the day.
"We looked at a number of markers, and there was no measurable difference in the effect that this type of dietary intervention had".
They selected 20 healthy participants who were regular bread eaters - getting about 10 percent of their calories from the bread, a globally typical figure.
After a week on their (incredible-sounding) high-bread diets, the participants took a two-week break, then swapped onto the other kind of bread for a week.
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.
They believe this is down to the individual's glycaemic responses - which measures the effect a food or meal has on blood sugar (glucose) levels after consumption and is dependent on the blend of microbes found in the gut.
Overall there was no difference between the two types of bread in terms of health effects.
By analyzing stool samples, researchers saw that the gut microbiome of each participant changed slightly depending on the type of bread they consumed.
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.
Some people may prefer brown bread while others favour white - but there has been little dispute that wholemeal is healthier. Some people responded well to one bread, while others didn't due to their gut bacteria.
But the authors pointed out that one issue that the study did not address was that many people eat less high fibre bread, such as wholewheat sourdough.
"Going for wholegrain bread and other wholegrain foods is important as, in the United Kingdom, we eat much less fibre than is recommended".
He added: "These findings could lead to a more rational approach for telling people which foods are a better fit for them, based on their microbiomes [a group of microorganisms such as bacteria and viruses]".
Professor Jebb warned that the lack of control group in the trial meant there may be other contributing factors to the results.
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.