Rye bread promotes a healthy microbiome

Research shows that rye bread is much easier on our blood sugar than plain old white or wheat bread. And now, a new study shows how consuming rye bread may do this.

Many attribute the better blood sugar response from rye bread to a higher amount of soluble fiber. But this new study indicates that it’s a little more intricate than that. Even cooler, it involves long term changes to the microbiome.

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Rye bread, the microbiome and betaine

There are likely many beneficial aspects of rye bread that make it a better choice than white or wheat. And while fiber is certainly something that improves our blood sugar response, that doesn’t mean it’s the only game in town.

To determine if some of these benefits come from the microbiome, researchers fed mice rye and wheat bran. Then, using a procedure called metabolomics, they looked to find if the microbiome was pumping out beneficial compounds.

Mice consuming both forms of bran saw increases in metabolites of something called glycine betaine. But, many of these metabolites aren’t found in rye bread. To be present, something must transform glycine betaine in to these metabolites. Consequently, the microbiome is an attractive target.

As it turns out, it’s actually a cool little process. When mice consume the bran, the intact bran feeds the microbiome in the colon. This increases numbers of many beneficial bacteria including:

  • Akkermansia
  • Lactobacillus
  • Bifidbacterium
  • Ruminococcus
  • Coriobacteriaceae
  • Parasutterella

These bacteria transform the glycine betaine found in bran in to metabolites that enter the blood. There, they circulate to tissues and cause beneficial effects.

To verify the microbiome as the source of these metabolites, they fed germ-free mice the same bran. There were significantly less betaine metabolites in the tissues of germ-free mice, they mostly contained glycine betaine.

Next, they used a human model of the microbiome to determine if the results would hold up in humans. Lo and behold the results were similar. To be clear, this is a model of the human microbiome, and not actually in living humans.


Rye bread causes a much more blunted blood sugar response than other types of bread. Often, people attribute this to higher soluble fiber levels. This data indicates that the microbiome is involved.

There was an increase in bacteria associated with better metabolic health. This change in the microbiome increased metabolites of glycine betaine that are also associated with better metabolic health. Furthermore, bacteria associated with poorer metabolic health decreased.

Overall, this data shows that the better blood sugar response from rye bread consumption is, at least in part, due to changes in the microbiome.

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