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Gut Microbiome and Optimal Health: Unleashing the Power of Probiotics and Fiber-Rich Foods

(Originally published in diaTribe Learn)

Written by: Jennifer McManus

What is the gut microbiome? There are five well-known organs that humans need to survive – the heart, lungs, brain, kidneys, and liver. However, some studies indicate there is a sixth “organ” that is imperative for human survival: the gut microbiome.

The gut microbiome, a collection of bacteria that live primarily in our large intestine, shapes our health in many ways including the prevention, development, and progression of multiple chronic diseases, including diabetes.

The microbes in our gut (and the byproducts they produce) have very important jobs in the human body as they are intimately involved in hormone production, protection against harmful bacteria and inflammation as well as digestion and absorption of the foods we eat.

Our gut microbiome starts to develop at birth with the method of delivery – vaginal vs. C-section – being an early determinant of gut microbiome diversity. Additionally, research shows that initial feedings – breast milk and/or formula – have a major impact on shaping the microbiome through infancy.

While we can’t control how we were born or what we were fed as an infant, there are many other controllable factors that impact our gut health and the microbes present throughout adulthood. These controllable factors include medications (especially antibiotics), diet, stress, sleep, environment, and lifestyle.

Why is the gut microbiome important?

Numerous studies have examined the gut microbiome in people with type 2 diabetes. It was found that specific bacteria were decreased in the gut of people with type 2 diabetes. Additionally, positive connections have been found between other bacteria and insulin sensitivity. All of this data points out that gut bacteria may have direct effects on how type 2 diabetes develops.

Another study found restoring those missing important bacteria (by taking probiotics) to be beneficial in the management of type 2 diabetes. Participants with type 2 diabetes were supplemented with five specific bacteria strains. After three months, they had a 0.6 change in their A1C levels and a 32.5% decrease in post-meal blood sugar spikes.

It is important to note that probiotics are not regulated according to “drug” standards by the U.S. Food and Drug Administration (FDA). Probiotics typically fall under “supplements” which are held to a different set of regulations than drugs. This means that some of the bacteria and ingredients used in probiotics have not been evaluated according to the strict safety measures that drugs are.

You are what you eat: what this really means and why you should care

Jana Davis, a private practice dietitian specializing in diabetes and nutrition, said she has found success working with many clients with diabetes by prioritizing gut health. “What we eat feeds and nourishes the trillions of bacteria in our microbiome,” she said. “We need to make sure we are eating a very diverse diet of high fiber vegetables and fruits in a variety of colors along with whole grains.”

The main source of food for the beneficial bacteria in our gut is fiber. High quality dietary fiber is found mostly in whole fruits, vegetables, nuts, legumes, whole grains, and seeds. Fiber is a type of carbohydrate that passes through the body completely undigested by the enzymes that release glucose molecules from ingested carbohydrates – meaning it will not impact blood sugar levels.

There are two different types of fiber – soluble and insoluble. They are both important, but they have completely different functions:

Soluble fiber:

  • Dissolves in water and forms a gel-like material

  • Feeds the gut microbiome

  • Helps slow the absorption of glucose

  • Reduces low-density lipoprotein (LDL) cholesterol

  • Helps to bulk your stool (think: slows things down)

Insoluble fiber:

  • Helps with colon health

  • Aids in digestion

  • Stimulates gut peristalsis (think: gets things moving)

Most fiber-containing foods tend to have some amount of both soluble and insoluble fiber, but there are foods that are higher in one versus the other. Based on your health goals, knowing which fiber to focus on will help you figure out which foods to eat.

Conversely, what we eat can also negatively impact the species in our gut. The typical American diet is high in fat and added sugar and low in fiber. Fiber is found mostly in plant-based foods such as whole fruits, vegetables, nuts, legumes, whole grains, and seeds.

“If we don’t have all of these important plant-based foods in our diet and the emphasis is more on animal protein, the chemical processes of many of these bacteria are different, and it can actually have a negative effect on the colon,” Davis said.

How to eat well to improve gut health for optimal diabetes management

Foods to eat

Fiber-containing foods

One of the main ways to improve gut health for optimal diabetes management is through soluble fiber. Soluble fiber provides a double whammy that helps slow glucose absorption while feeding and nourishing gut microbiome. As we learned in the previous section, fiber is found mostly in whole fruits, vegetables, nuts, legumes, whole grains, and seeds.

Here is a list of highly beneficial soluble fiber-containing foods to help improve gut health:

  • Apples

  • Avocados

  • Barley

  • Beans

  • Broccoli

  • Brussels sprouts

  • Carrots

  • Citrus fruits

  • Oats

  • Peas

  • Pears

  • Sweet potatoes


Prebiotics are non-digestible fibers that provide food for the beneficial bacteria (probiotics) that reside in the gut. Once these prebiotic foods reach the large intestine, they are fermented by the gut bacteria. This provides energy for these bacteria to grow and thrive which has a positive impact on gut health. Good sources of prebiotics include:

  • Asparagus

  • Garlic

  • Green bananas

  • Jerusalem artichokes

  • Leeks

  • Onions

  • Whole grains

Fermented foods

You can also eat your probiotics through fermented foods. These foods contain live microorganisms that have health benefits when consumed. Yogurt is one of the most well-known sources of probiotics. Look for brands that have the least amount of “added sugar” and specifically say they contain live, active cultures as these are the ones that will provide the most benefit to your gut health.

Besides yogurt, you can also find probiotics in other fermented foods:

  • Kefir

  • Kimchi

  • Miso

  • Sauerkraut

  • Tempeh

Foods to avoid

Processed foods

Avoid highly processed foods, sugar-sweetened beverages, and refined carbohydrates such as:

  • Baked goods (pies, pastries, cakes, etc.)

  • Candy

  • Chips

  • Fried food (French fries, chicken fingers, fish sticks, etc.)

  • Ice cream

  • Juices

  • Processed meats (sausages, cured meats, deli meats, etc.)

  • Sodas

An excessive intake of added sugar and saturated fats has been shown to create an imbalance within the microbiome, often referred to as “dysbiosis,” leading to chronic inflammation that often precede metabolic diseases (diabetes, obesity, cardiovascular disease, etc.).

Alcoholic beverages

Clinical data suggests that alcohol consumption is associated with unfavorable changes in the gut microbiome and may be associated with increased inflammation and decreased integrity of the intestines. On the bright side, there is one type of alcohol that has been shown to provide some benefit to the gut microbiome – red wine. Red wine contains polyphenols which are beneficial antioxidants. The polyphenols in red wine have been found to act as a prebiotic (food for probiotics) and promote the growth of certain probiotics (beneficial bacteria).


Ultimately, our gut microbiome shapes our health through the prevention, development, and progression of disease. It is important to take care of our gut microbiome by being mindful of what we are putting in it – from food and drinks to specific beneficial bacteria known as probiotics.

Overall, prioritizing fiber, avoiding processed foods, consuming a variety of fermented foods, and limiting alcohol intake will have a beneficial impact on the health of our microbiome.

Editor’s Note: Jennifer McManus is a registered dietitian and gut health expert. She is also a current employee at Pendulum, a manufacturer of probiotic products for gut health.

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