Whole-grain sourdough sounds healthier than refined white bread. But according to research published in Cell Metabolism, they may not actually be that different in the short term. The study found that, while different people had varying responses to the two breads, the breads didn't have significantly different effects within individuals. For the study, researchers divided 20 healthy men and women, ages 24 to 53, into two groups: the first group ate 145 grams of whole-grain sourdough bread, and the second group ate 110 grams of refined white bread, everyday with breakfast for a week. These portions were chosen because they each provided 50 grams of digestible carbohydrates. After breakfast, both groups could eat as much as they wanted of their respective breads, while avoiding other wheat products. They tracked their daily diets in food diaries, and, after a two-week break, the groups swapped bread types and the week-long trial was repeated. However, this time, their bread portion was restricted to match the portion they ate during the first trial. To understand how each bread affected the participants, researchers measured their fasting blood sugar levels, blood sugar responses (glycaemic response) to the breads, and an array of nutritional and metabolic parameters at the beginning and end of the two trials. At the same time, they analysed each participant’s intestinal microbiome. The researchers found that:

• The white bread and whole-grain sourdough bread triggered the same glycaemic response in the participants.
• Changes in other clinical tests were the same after one week of white bread consumption as after one week of whole-grain sourdough consumption.
• Neither of the two types of bread had a significant effect on the participants’ gut microbiomes.
• Although responses to the two types of bread were the same within individuals, they varied greatly between individuals and were found to be associated with certain aspects of their gut microbiome.

These findings suggest that, for certain health markers, the type of bread you eat might not matter as much as the make-up of your gut microbial community. While longer trials would be needed to determine how bread-eating habits affect health, it’s no surprise that diets are not one-size fits all. If you’re interested in developing an eating pattern that’s tailored to your needs, a doctor or nutritionist is the best way to go.

Source: Cell Metabolism