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  • A recent study analyzed associations between 36 bacteria found in the gut and a person’s ability to maintain healthy insulin levels.
  • They found 10 bacteria associated with a lower rate of blood sugar levels fluctuating abnormally.
  • The study is part of an ongoing, prospective study led by researchers at Cedars-Sinai Medical Center.

Type 2 diabetes (T2D) is a disease that occurs when the body doesn’t sufficiently produce or use the hormone insulin, which causes blood sugar levels to rise.

As the most common form of diabetes, T2D has affected about 462 million individuals globally, or 6.28% of the population in 2017, according to a 2020 estimate.

The Centers for Disease Control and Prevention (CDC) reports that risk factors for T2D include:

  • being age 45 or older
  • having overweight or obesity
  • having a parent, brother, or sister with type 2 diabetes

Some risk factors for T2D, such as diet, are modifiable. For instance, a 2022 study shows that a high quality diet is associated with a nearly 30% lower risk of developing the disease.

For years, researchers have worked to understand whether the gut microbiome, which encompasses billions of microorganisms that live in the human digestive tract, plays a role in the development of diabetes.

Recently, researchers at Cedars-Sinai Medical Center in Los Angeles, CA, published early results from an ongoing, prospective study about the gut microbiome and diabetes. They found 10 types of bacteria that are associated with a lower rate of abnormally fluctuating blood sugar levels.

The findings were recently published in the journal Diabetes.

Cedars-Sinai researchers found that people with higher levels of gut bacteria from a group called Coprococcus tend to have higher insulin sensitivity.

Additionally, they discovered that gut microbiomes with higher levels of Flavonifractor tended to have lower insulin sensitivity.

“Insulin sensitivity refers to the response of tissues such as the liver, muscle, and fat to insulin in its ability to regulate blood sugar,” Dr. Mark Goodarzi, Ph.D., director of the Endocrine Genetics Laboratory at Cedars-Sinai, senior author of the study and principal investigator of the multicenter study called Microbiome and Insulin Longitudinal Evaluation Study (MILES) explained to Medical News Today.

“High insulin sensitivity indicates a good response to insulin. Low insulin sensitivity (also called insulin resistance) refers to low responses of these tissues to insulin. Most people with insulin resistance compensate by producing more insulin. When insulin production is insufficient to deal with insulin resistance, blood sugars rise and type 2 diabetes occurs.”

– Dr. Mark Goodarzi, Ph.D., senior study author

In the last several years, multiple studies, including this one from 2012, have found that individuals with type 2 diabetes have lower levels of a certain type of bacteria that produces a type of short-chain fatty acid called butyrate.

“Many prior studies have suggested that butyrate-producing bacteria promote better insulin sensitivity and protection from diabetes,” Dr. Goodarzi said. “Our study specifically examined such bacteria.”

The researchers found that while most bacteria that produce butyrate were associated with better insulin sensitivity, a few were associated with insulin resistance.

“This provides an important message regarding this group of bacteria,” Dr. Goodarzi explained. “If modulation of the gut microbiome becomes a method of preventing or treating diabetes, we have to carefully choose which bacteria to modulate.”

For the study, investigators analyzed data from 353 people who had not previously been diagnosed with diabetes. Of the participants, 224 were non-Hispanic whites, and 129 were African-American.

None of the participants had recently experienced severe gastrointestinal illness or used medicines like antibiotics that could impact the microbiome.

Participants took an oral glucose tolerance test and filled out a diet questionnaire.

Researchers found 28 of the participants had diabetes, and an additional 135 were classified as having prediabetes. Participants with diabetes and prediabetes were combined into a single group and were compared with the 189 participants with healthy glucose tolerance.

Participants were asked to collect a stool sample 1–2 days before coming to the clinic. Researchers later conducted genetic sequencing on the stool samples to study the participants’ gut microbiomes.

The research team analyzed associations between participants’ ability to maintain healthy levels of insulin and 36 butyrate-producing bacteria found in the stool samples, controlling for factors that could contribute to the participants’ diabetes risk, such as:

Researchers found that participants with abnormalities in blood glucose levels were older, more often male, and had higher BMI.

They discovered that Coprococcus and related bacteria had beneficial effects on insulin sensitivity. But Flavonifractor, despite producing butyrate, was associated with insulin resistance.

The analyses found 10 bacteria associated with a lower rate of blood sugar levels fluctuating abnormally and two bacteria associated with adverse associations on blood sugar levels.

“These results suggest that increasing Coprococcus and related bacteria or decreasing Flavonifractor may improve insulin sensitivity and prevent diabetes,” Dr. Goodarzi told MNT.

“Future research (in cellular systems, animal models, and humans) will be needed to prove the cause-and-effect relationships between these bacteria and diabetes. If so proven, clinical trials will be the next step to determine whether modulating these bacteria (via prebiotics, probiotics, or antibiotics, depending on the bacterial targets) are a viable option to prevent or treat diabetes.”

– Dr. Mark Goodarzi, Ph.D., senior study author

Dr. Goodarzi told MNT it’s too early in the research to recommend that individuals try to change their gut microbiome to reduce their risk of developing diabetes.

“At this time, these results do not mandate any changes in terms of healthy or unhealthy diet or lifestyle factors,” Dr. Goodarzi said.

“Future research will be needed before recommendations can be made based on these findings.”

For individuals looking to promote their gut health in general, Dr. Goodarzi said there’s “good evidence that a high fiber diet may accomplish this goal.”

Kristin Kirkpatrick, R.D., a registered dietitian and author based in Colorado, pointed out to MNT that prebiotic fiber has many documented benefits to support gut health. Sources of prebiotics include:

  • onions
  • chicory root
  • oats
  • bananas
  • Jerusalem artichokes

Roxana Ehsani, R.D., a registered dietitian nutritionist and sports dietitian located in Miami, FL, and Kirkpatrick both suggested eating more fermented foods to improve gut health.

Ehsani suggested kefir for people looking to improve their gut health. “It’s almost similar to a drinkable yogurt,” she told MNT. “You can use it in place of milk or yogurt in a smoothie.”

Other examples of fermented foods include:

  • saurkraut
  • kombucha
  • tempeh
  • kimchi