Gut Bacteria and Diabetes: What Is the Connection?

02/21/2023 | 7 min. read

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diabetes and gut

The CDC reports that more than 37 million Americans (11.3% of our population) have diabetes, and 90%–95% of them have type 2. Another 96 million (one in three adults) have prediabetes, meaning they are at increased risk of developing type 2 diabetes within the next five years.

Equally disturbing is the increase in diabetes in young people. Years ago, type 2 diabetes was called adult-onset diabetes, but that term is no longer used because children and teens are now developing this condition, and it’s happening at an alarming pace.

You probably know quite a bit about type 2 diabetes. You know it’s marked by high blood sugar and insulin resistance. You know that obesity and abdominal fat, a poor diet, and inactivity are primary risk factors.

What most people don’t know is that the gut microbiome—the immense collection of bacteria and other microbes in the intestinal tract—also has an effect on blood sugar metabolism, insulin sensitivity, weight, and the risk of developing type 2 diabetes.

What You Need to Know About Type 2 Diabetes

The underlying cause of prediabetes and type 2 diabetes is insulin resistance. The cells fail to properly respond to insulin’s signals to let glucose in, so blood sugar is elevated above normal levels.

What Are the Symptoms of Type 2 Diabetes?

Most of the time people who have type 2 diabetes have no symptoms, which is why this condition often goes undiagnosed. When symptoms do show up, they may include:

  • Increased thirst (polydipsia)
  • Increased urination (polyuria)
  • Nighttime urination (nocturia)
  • Fatigue
  • Blurred vision
  • Frequent infections
  • Slow healing sores

How Is Type 2 Diabetes Diagnosed?

If you have none of these signs or symptoms, how can you know if you have an issue with blood sugar regulation? Fortunately, there are several blood tests for diagnosing diabetes, including fasting glucose, hemoglobin A1C (HgA1C), and glucose tolerance testing. Levels indicative of diabetes are:

  • Fasting plasma glucose over 126 mg/dl
  • Hemoglobin A1C above 6.5%
  • Two-hour plasma glucose over 200 mg/dl post-oral glucose tolerance test

What Are the Risk Factors for Type 2 Diabetes?

Several well-studied factors are linked with an increased risk of developing type 2 diabetes:

  • Being overweight or obese
  • Increased belly fat
  • A diet high in sugars (including high fructose corn syrup!) and processed carbohydrates
  • Lack of exercise
  • Family history
  • Aging
  • Gestational diabetes
  • Prediabetes

More recent research has confirmed another, often overlooked contributor: gut health and the makeup and diversity of your gut microbiome.

The Gut Connection to Diabetes

It is obvious that the foods you eat can have a direct impact on your blood sugar. For example, I don’t recommend starting your morning off with a glass of orange juice, a bagel with jam, a donut, or coffee cake—which are all really desserts in disguise.

These fast-burning carbohydrates, which are quickly broken down in your digestive tract, not only spike your blood sugar but also cause you to reach for more sugar and carbohydrates later in the day. It’s a vicious cycle that becomes difficult to break. Over time your body becomes resistant to insulin, and glucose cannot enter your cells as efficiently as before. Thus, the need for more sugar and carbs to make you feel good!

Much better breakfast choices include two to three scrambled eggs plus a quarter of an onion and two cups of chopped Swiss chard, sautéed in avocado oil or coconut oil, with half an avocado on the side.

These foods put less strain on your pancreas to produce insulin and, compared to the orange juice and bagel breakfast, will keep your blood glucose levels in a lower, healthier range. Plus, you will be much more satiated and likely feel better as the day progresses. That’s because your blood sugar will be stable, and you will not be dependent on more sugar and carbs to boost your energy or mood.

Gut Microbiome-Diabetes Link

What may not be so obvious is that the health of your gut microbiome can affect your metabolism and influence your blood sugar just as food does.

Research on the gut microbiome has snowballed over the past three decades. We now know that the trillions and trillions of bacteria, yeast, and other microbes that make up the gut microbiome play essential roles in many aspects of our health and well-being. Effects that are directly or indirectly related to diabetes include:

  • Blood sugar and insulin: Some gut bacteria produce butyrate and other short-chain fatty acids (SCFAs), which have been shown to affect the body’s ability at the intestinal level to produce glucose (gluconeogenesis). These SCFAs can have a downstream effect on insulin release as well.
  • Weight: Nutrient absorption, energy utilization, and fat storage are all influenced by the gut microbiome. It even impacts your appetite! Each person’s microbiome is unique, but important differences have been noted in the microbial composition of obese versus lean individuals.
  • Inflammation: A diverse, balanced microbiome protects against leaky gut (intestinal permeability), which triggers inflammation—another risk factor for diabetes.

Bottom line, as researchers reported in Gut Microbes, “Unequivocal evidence demonstrates that gut microbes influence whole body metabolism by affecting the energy balance, gut permeability, metabolic endotoxemia, and inflammation that are associated with several metabolic disorders.”

Ways to Improve Your Blood Sugar and Gut Health

You can help improve your blood sugar by experimenting with these simple food-related tips. They will likely improve your metabolism and blood sugar regulation by supporting the health and diversity of your gut microbiome.

  • Say no to sugar. You may feel good temporarily with a sugar high, but long term these foods don’t serve you in any way. In a 2022 study, researchers from Columbia University found that dietary sugar alters the gut microbiome and can cause weight gain, insulin resistance, and elevated blood sugar. Artificial sweeteners are no solution, as they also have an adverse effect on gut microbes and can actually increase metabolic disorders.

  • Eat more fiber-rich vegetables and fruits. Fiber provides fuel for your gut bacteria to produce SCFAs. Some produce is rich in prebiotics, a type of fiber that is particularly supportive of beneficial bacteria. A plant-based diet has been linked with a more diverse and stable gut microbiome.

  • Include probiotic foods. Yogurt, sauerkraut, miso, and other fermented foods have a well-deserved reputation for their health benefits, and a main reason is because they contain beneficial bacteria that supports the gut microbiome.

  • Make sure you consume an adequate amount of healthy fats and protein. Doing this with each meal will help balance blood sugar levels.

  • Stop eating when you feel 80% full. This may seem trivial but eating too much is all too common these days, and we’re finding more and more that calorie restriction is very beneficial for your gut and overall health!

  • Take probiotic supplements. I recommend probiotics for many of my patients. Even if your diet is exemplary, by helping replenish beneficial species probiotics provide an extra layer of protection for your gut microbiome.


At this point, there is still much to be learned about the gut microbiome and how to manipulate it for optimal health. Furthermore, gut microbes are just one aspect of blood sugar metabolism—and diet is just one aspect of metabolic health. Exercise, weight loss, stress reduction, restful sleep, detoxification, and blood sugar-lowering supplements are additional components of a comprehensive natural program for diabetes.

That said, gut microbes do play an important role in glucose metabolism, weight, inflammation, and related factors. By adopting the above suggestions, you are taking a giant step on your journey to better gut health and blood sugar control.


Dr. Drew Sinatra

Meet Dr. Drew Sinatra

Dr. Drew Sinatra is a board-certified naturopathic doctor and self-described “health detective” with a passion for promoting natural healing, wellness, and improving quality of life by addressing the root cause of illness in patients of all ages. His vibrant practice focuses on treating the whole person (mind, body, and spirit) and finding missed connections between symptoms and health issues that are often overlooked by conventional medicine.

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