You’ve probably heard of or even consumed probiotics, which are a collection of microorganisms (in your gut or in fermented foods such as yogurt) that confer health benefits when ingested at certain levels. In order for probiotics and other beneficial microorganisms to thrive, they need to be nourished by prebiotics — fermentable fibers found in fruits, vegetables, and whole grains. Prebiotics have numerous health benefits, including enhancing nutrient uptake, lowering bad cholesterol, reducing risk of colon cancer, boosting the immune system, and improving metabolic health. Here, we focus on the beneficial effects of prebiotics on glucose management, which is especially important for people at risk for metabolic disorders such as diabetes.

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How do prebiotics work?

All prebiotics are fibers, but not all fibers are prebiotics. To be considered a prebiotic, a fiber must:

• Not be digestible by mammals
• Be fermentable by gut microbes
• Improve the activity and viability of gut microbes

There are two main types of fibers, soluble and insoluble: 

• Soluble fibers dissolve in water and work like an aquatic vacuum cleaner, clearing the digestive tract of substances such as metabolic waste products, allergens, and carcinogenic chemicals. Good food sources include oats, beans, peas, citrus, carrots, and barley.
  
  
• Insoluble fibers do not dissolve in water. Instead, these fibers travel through the digestive tract, absorbing fluid and adding bulk to your stool, which can help relieve constipation and make bowel movements more regular. Good food sources include whole wheat, nuts, bran, potatoes, green beans, and cauliflower.

How prebiotics affect glucose levels

Now, let’s take an even deeper dive into how prebiotics benefit human health by looking at one of the main mechanisms at play. Prebiotics serve as precursors to beneficial substances such as vitamins, indole derivatives, neurotransmitters, and metabolites. 

One of the most important metabolite groups are the short-chain fatty acids (SCFAs): in particular, acetate, propionate, and butyrate. Among the many benefits of SCFAs, they (1) help maintain a robust intestinal lining; (2) increase the production of protective gut mucus while also reducing inflammation and protecting against harmful bacterial infection; and (3) positively affect energy and glucose metabolism in the liver, and contribute to increased glucose homeostasis (meaning that glucose levels are less likely to rapidly fluctuate).

Why you should manage your glucose

Blood glucose levels are influenced by a number of factors including genetics, metabolic and physical health, sleep, stress, and diet. Our bodies function best when glucose levels stay within a narrow range. If blood glucose levels get too low, we can lose the ability to think straight and function normally. In contrast, sustained high levels of blood glucose can lead to organ damage. After we eat, the carbohydrates in our food get broken down into glucose, which circulates in the blood. This rise in blood glucose levels stimulates the release of insulin, which promotes cellular uptake of glucose for energy use. 

If you have diabetes, it’s especially important to monitor your blood glucose levels to see how well your current treatment regimen is working. If you’re using insulin, then blood glucose monitoring can be a powerful tool for understanding how your body is responding, which will allow you to get information on how to manage glucose on an hourly basis.

The following are examples of things that can raise your blood glucose levels:

• Eating carbohydrates
• Consistent lack of exercise
• Stress
• Smoking
• Dehydration
• Certain medications

In contrast, low blood glucose can result from:

• Skipping meals
• Exercise
• Certain medications

The two main ways to monitor your blood glucose include:

Glucose meters and test strips. Although there are many types of glucose meters available, most of them work in the same way. First, a test strip is inserted into the meter. Then, a special needle is used to poke your finger. Gently touching the test strip to the blood on your fingertip allows the blood to be drawn into the strip, where the meter can measure glucose levels.

Continuous glucose monitors (CGMs). As the name suggests, CGMs are a wearable device that attaches to your skin and continually measures your glucose levels. They wirelessly transmit glucose data to a device or app (like the January app) to provide you with a stream of glucose data.

Whatever method you choose to use to monitor your blood glucose, you and your healthcare provider will gain valuable insight into how to manage your blood glucose levels.

Symptoms of poor glucose management

While small fluctuations in glucose are normal, large swings can make you feel:

• Dizzy
• Lightheaded
• Excessively hungry or thirsty
• Anxious
• Tired

In addition, you may experience headaches, vomiting, confusion, blurry vision, rapid heartbeat, unexplained weight loss, stomach pain, and more.

Chronically poor glucose management can eventually lead to heart disease, vision loss, or kidney disease. In addition, upward trends in blood glucose can result in low-grade inflammation, increasing the risk for prediabetes development. Although glucose levels in prediabetes are lower than in full-blown diabetes, this elevated glucose can lead to chronic organ damage, so it’s best to address prediabetes as soon as possible by changing your diet, increasing your exercise regimen, and managing stress as best as you can.

The role of a fiber-rich prebiotic diet for managing glucose levels 

Especially for those at risk for diabetes, or who already have early symptoms (pre-diabetes) or a definitive diagnosis of type 2 diabetes (T2D), embracing a multi-pronged plan of non-pharmacological treatments for blood glucose control is imperative, and includes many lifestyle modifications. But this same lifestyle guidance really should apply to all of us who want to reduce our risk of the many chronic disorders that can eventually develop from aberrant blood glucose levels. 

In addition to increasing exercise and hydration, halting smoking and excessive alcohol consumption, and improving your sleep hygiene, a healthy diet is of vital importance to regulating your blood glucose levels. In brief, such a diet incorporates:

• Caloric restriction overall (to reduce or maintain weight)
• Moderation of high-glycemic, low-fiber carbohydrates; and increased consumption of high-fiber whole foods — that’s where prebiotics come in to play
• A sharp reduction in the consumption of processed foods
• Avoidance of unhealthy saturated and trans fats, and increased intake of healthy fats and omega-3 fatty-acid-containing fish
• An overall moderation of sodium intake 

A Mediterranean diet is a great place to start. This diet is rich with plant-based foods that have high fiber levels. Eating foods with high fiber levels not only induces feelings of fullness faster, but helps your gut microbes produce the SCFAs that help control your blood sugar levels. Other benefits include lower blood cholesterol levels, boosted no doubt by the diet’s rich amount of unsaturated fats, such as olive oil. 

A diet/lifestyle disclaimer re: hyperglycemia

To be realistic, many individuals with chronic hyperglycemia do indeed progress to T2D, and some may not be able to reverse their T2D through non-pharmacological interventions alone. However, even in cases where pharmacological management becomes recommended, it is nonetheless vitally important for these individuals to adhere to healthier lifestyle changes, including the best dietary regimen.

For those not yet in need of medication, bear in mind that research has shown that lifestyle/diet interventions alone can reduce the incidence of diabetes by a significant percentage: a 2002 New England Journal of Medicine study documented a 58% reduction in diabetes (vs. control group) in a high-risk population after three years of an intensive lifestyle and diet program. 

Which prebiotics are best for glucose management?

As mentioned earlier, prebiotics play an important role in regulating glucose levels. In fact, the Centers for Disease Control (CDC) lists “eating a healthy diet with plenty of fruits and vegetables” as the first strategy for managing blood glucose levels. These high-fiber foods are also particularly beneficial for overall metabolic health, and there are tools that can show you what foods are better for blood glucose levels. For example, the glycemic index (GI)  was developed to show how certain foods affect your blood sugar levels; low or medium GI values (such as those found in whole grains, fish, yogurt, sweet potatoes, most nuts and legumes) are better for managing glucose. Another tool, glycemic load (GL), tells you how quickly a food causes glucose to enter the bloodstream and how much glucose you’ll get per serving. The international database created by researchers at the University of Sydney in Australia allows you to check both GI and GL.

Here are some examples of low-to-medium-GI foods that can improve glucose management:

• Vegetables: A pair of preclinical studies demonstrated that carrot nutrients and vegetable juice can lower blood glucose levels. In addition, a clinical study showed broccoli sprouts can improve the insulin response in type 2 diabetes (T2D). Other vegetables that may have a positive effect on blood glucose levels include lettuce, okra, cauliflower, bok choy, and spinach.
  
  
• Fruits: A set of observational studies correlated whole fruit consumption (such as blueberries, grapes, and apples) with decreased risk for developing T2D. If you can tolerate the taste, bittermelon is another great option for countering diabetes. Other whole fruits that may be beneficial for blood glucose control include bananas, pineapple, raisins, and cherries.
  
  
• Legumes: Legumes such as kidney beans, chickpeas, and lentils can reduce cardiovascular risk factors for developing T2D such as A1C, which is a measure of blood glucose levels.
  
  
• Nuts and seeds: A large meta-analysis found nut consumption reduced the risk for developing diabetes and cardiovascular diseases. (It’s important to note that any coatings on nuts such as chocolate or honey can raise the GI value, which can reduce the efficacy for managing blood sugar. Therefore, it’s best to consume raw nuts whenever possible.) Similarly, certain seeds such as chia seeds also have positive benefits on controlling blood glucose.
  
  
• Whole grains: Not all grains and flour are created equal, and whole grains such as whole wheat, brown rice, and oats can reduce the risk of developing T2D by improving glycemic control. Importantly, the less processed, the better!

Adding a prebiotic-rich supplement to your dietary regimen

If adhering to a consistent dietary regimen that keeps your blood glucose levels in line proves challenging, it’s worth considering a synbiotic supplement, as research has demonstrated that because synbiotics combine prebiotics and probiotics in one formulation, they can benefit fasting glucose levels — as shown in this 2021 randomized controlled trial on obese individuals. The scientists at Eden’s tested dozens of prebiotic fibers before selecting the following five for its 3-in-1 Synbiotic Supplement (which also contains probiotics and polyphenols). The particular benefits of these selected prebiotics, especially for glucose management. are as follows:

Resistant potato starch has many health benefits, including improving intestinal function, carbohydrate and lipid metabolism, and managing weight. A recent human trial showed that in people at risk for developing T2D, a diet consisting of potato resistant starch supplementation lowered fasting blood glucose levels.

Locust bean gum comes from the carob tree and can reduce cholesterol and may be beneficial in controlling colon cancer and heart disease. A preclinical study demonstrated locust bean gum can reduce the glucose response after food intake, primarily through its fiber properties. There could be other benefits to glucose absorption, but more studies are needed.

Guar gum comes from guar beans and is frequently used as a food thickener. A human study and a clinical trial both found positive effects of guar gum on glucose and insulin control, as well as cholesterol levels, but only in diabetics.

Oat bran has demonstrated, in numerous studies, positive effects on blood glucose levels in T2D patients, pregnant people with gestational diabetes, and even healthy individuals. Oat bran also delays gastric emptying — the time it takes for food to move out of the stomach — thus making you feel fuller for longer.

Barley beta glucan, much like the prebiotics mentioned above, decreases post-meal glucose surges and improves the insulin response, especially in people at risk for developing diabetes.

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Key takeaways

Prebiotic fibers play a vital role in maintaining gut health by supporting probiotics and serving as precursors to beneficial metabolites, such as SCFAs. While many of its benefits are attributed to gut health, prebiotic digestion can affect other body systems as well, such as the cardiovascular system. An ongoing area of research includes the effects of prebiotics on glucose management, which is critical given the rising number of people at risk of developing diabetes and other metabolic disorders. Prebiotics are readily obtainable if you adhere to a high-fiber diet, such as the Mediterranean diet, which concentrates on eating fruits and vegetables, whole grains, legumes, and nuts and seeds (along with lean proteins, plenty of fish, some probiotic foods such as yogurt, and a modest amount of other dairy foods). Within a diet rich in prebiotic foods, concentrating on those with a lower glycemic index (GI) profile might benefit your glucose levels even more. It may also be of benefit to supplement your diet with a synbiotic, such as Eden’s, because its unique blend of prebiotics, probiotics, and polyphenols have been carefully formulated to confer many health benefits, including managing blood glucose. Before beginning a synbiotic regimen, be sure to talk with your healthcare provider to see if this strategy is right for you.