Here’s a diabetes paradox.

While most people who get type 2 diabetes are overweight or obese, some overweight/obese people never get diabetes—even those with elevated blood sugar levels and prediabetes!

What’s protecting them? One possibility is the beneficial bacteria living in their guts. Ironically, the best way to foster these good-for-you bugs may be to eat foods that you may be trying to avoid in the search for diabetes prevention!

Background: There is growing evidence that the “gut microbiome”—the collection of helpful organisms living in the gut that play a key role in digestion—influences type 2 diabetes risk.

Study: Researchers from Finland and Sweden compared two groups of people who had participated in the Finnish Diabetes Prevention Study, which began in the 1990s with more than 500 adults who were at high risk of developing diabetes because they were overweight and had high blood sugar. Like the American Diabetes Prevention Program, the Finnish program focused on lifestyle change to stop progression to diabetes. Fifteen years later, 52% of the participants remained free of the disease.

The researchers compared 104 individuals who remained diabetes free for 15 years with 96 individuals who developed diabetes within the first five years of the study. They looked closely at levels of various metabolites—by-products of digestion—to see whether there were big differences between the two groups. They compared diets, too.

Results: In participants who had not developed diabetes, there were much higher blood levels of indolepropionic acid. This compound, produced by beneficial bacteria in the gut, is known to protect the ability of beta cells in the pancreas to secrete insulin. The compound also improves insulin sensitivity—making insulin more effective. Both reduced insulin sensitivity and flagging insulin production are linked to developing type 2 diabetes.

Surprising finding: Higher levels of indolepropionic acid were also associated with lower levels of C-reactive protein, a marker of inflammation throughout the body. High levels of C-reactive protein can signal an increased risk for heart disease.

Diet connection: When the researchers looked at the participants’ diets, they found that higher levels of indolepropionic acid were associated with high fiber intake…particularly from whole grains, especially rye. And, as it turns out, whole grains’ fiber stimulates gut bacteria that convert the amino acid tryptophan from protein-rich foods into…indolepropionic acid.

These results not only back up the observation that people who have high-fiber diets are less likely to develop diabetes, but they also help explain why high-fiber diets are protective against diabetes.

Bottom Line: Weight loss and exercise remain the cornerstones of diabetes prevention. But a healthy diet that supports “good bugs” is important, too.

Many people, when they find out they’re at risk for diabetes, cut way back on carbohydrates—often as a way to lose weight. That can backfire by cutting out sources of gut-friendly high-fiber foods. A diet rich in fiber and whole grains, such as whole-grain rye and steel-cut oatmeal, is good for everyone, but it may be especially protective if you’re at high risk for diabetes.

For a healthy microbiome, according to Bottom Line medical editor Andrew Rubman, ND, you’ll also want to include plenty of fresh fiber-rich fruits and vegetables—both raw and cooked—as well as beans.

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