Dive Brief:

• Dietary advice to eat whole wheat bread instead of white bread may be misguided, as new research suggests the effects of the ingredients may vary from person to person, reports Baking Business.

• The study, published in Cell Metabolism, looked at 20 participants’ responses to either white bread or whole wheat sourdough, after eating each for a week. The glycemic index of the two breads was considerably different: 70 for the white bread and 54 for the whole wheat bread. However, not everyone reacted to the same bread in the same way. Some individuals showed a higher glycemic response to one type of bread, while some had a higher response to the other.

• The researchers also analyzed the participants’ gut bacteria and found it was the only way to predict their glycemic response to the different kinds of bread. “Understanding the interpersonal variation in the effect of bread, one of the most-consumed staple foods, would allow the personalization of bread-related nutritional recommendations and optimization of food choices worldwide,” researchers wrote.

Dive Insight:

Current advice to choose whole grains is based on a large body of research that links their consumption to better heart health; reduced risk of cancer, diabetes and obesity; and better glycemic control. The researchers behind this latest study acknowledge that any challenge to the benefits of whole grain consumption could have far-reaching consequences. However, they argue that some studies have not shown any effect, and others have suggested that whole grain consumption could even reduce mineral absorption.

Despite some contradictory studies, the message that whole grain bread is healthier than white is widely accepted — and with good reason, as the vast majority of research supports current dietary advice.

Although this latest study suggests that breads’ healthfulness may depend on individual systems, it is important to note that it only looked at 20 individuals over a couple of weeks. Meanwhile, long-term dietary reviews strongly suggest that people who eat more whole grains tend to live longer. The differences in this study could also be explained by the fact that whole grains and whole grain flour are not the same. How thoroughly a person chews food, or how finely milled the flour is may affect its glycemic index.

Still, many American consumers continue to choose white bread — 40% of Americans never eat any whole grains at all, according to studies cited by the Oldways Whole Grains Council — and Gallup found that 29% of the population is actively trying to avoid carbohydrates.