The link between gut bacteria and type 2 diabetes explained
The gut microbiome is a living ecosystem that exists deep within our gut and is intimately linked to our health. Like any ecosystem, the gut microbiome is vulnerable to change and these changes can either help or hurt us.
Decades of research have shown us that changes in our microbiome that increase the presence of specific types of bacteria may help protect us from conditions like type 2 diabetes.
On the other hand, the gut microbiome can also grow to exclude these beneficial bacteria, resulting in an increased likelihood of developing type 2 diabetes.
Fortunately, there are ways for you to tend to your microenvironment; steps you can take to encourage the growth of the good bacteria and reduce the influence of the bad bacteria.
In the following sections, we’ll explore the link between the gut microbiome and human health, with a specific focus on the types of bacteria that are believed to protect us from type 2 diabetes and what may cause these bacteria to disappear.
TABLE OF CONTENTS
- The link between type 2 diabetes and the gut microbiome
- How does the lack of certain strains of gut bacteria lead to type 2 diabetes?
- What specific strains of bacteria affect type 2 diabetes?
- Final Thoughts
- Additional FAQs
The link between type 2 diabetes and the gut microbiome
There is a close relationship that exists between the gut microbiome and human health. Both are capable of influencing the other in ways that we don’t fully understand yet.
However, research over the past few decades, carried out using everything from Petri-dishes to mice to humans, has uncovered a particularly strong link between the development of type 2 diabetes and the bacteria inside your gut.
The gut microbiome is home to trillions of individual bacteria, each belonging to one of hundreds of potential species. It is often described as being similar to rainforests or tide pools—ecosystems where many diverse species co-exist in some state of competition and harmony.
And, like these other ecosystems, the gut microbiome is vulnerable to change.
What species of bacteria live in your gut depend on several factors including:
- Your diet
- Your exercise levels and routines
- Medicine you may be taking
- Travel to foreign countries
- Your stress levels
- Your sleep habits
- Your genetics
Because of this, the exact composition of any one person’s microbiome might change over time and can differ from another person’s1.
Sometimes, these differences are meaningless. But other times, when specific types of bacteria are missing, it could lead to type 2 diabetes1.
For example, multiple studies have found that species belonging to the genera of Bifidobacterium, Bacteroides, Faecalibacterium, Akkermansia, and Roseburia were often missing (or severely reduced) in people who have type 2 diabetes1.
That these bacteria are missing in people with type 2 diabetes suggests that they may play an important role in protecting us from various metabolic conditions, such as diabetes and obesity.
How does the lack of certain strains of gut bacteria lead to type 2 diabetes?
The effects of losing a type of bacteria from the gut microbiome can vary depending on the strain; however, the types of bacteria that are frequently absent in people with type 2 diabetes tend to be ones that do one of three things:
- Strengthen the gut mucosal lining
- Prompt the release of certain metabolic hormones and butyrate
- Reduce inflammation in the gut
Each of these functions is important to our health, and the loss of the bacteria responsible for carrying out these activities can leave a person vulnerable to several conditions, including type 2 diabetes.
1. Butyrate production
Many of the strains of bacteria that are missing in people with type 2 diabetes are involved in the production of butyrate—an important molecule that can be used for energy by the cells that line the colon (colonocytes) and can act like a hormone in certain contexts4.
Put simply, butyrate is an incredibly important molecule with far-reaching effects on the human body.
Butyrate is produced in the large intestine as a byproduct of soluble fiber metabolism. Dietary fibers are complex molecules that human cells are unable to breakdown. Were it not for some species of bacteria in the gut, dietary fibers would go right through us. Fortunately, though, there are bacteria in the gut microbiome that use fiber like food—they consume it by breaking it down and stripping it for useful parts. In this process, butyrate is made and cast aside5.
Once made, most of the butyrate is used by cells in the gut called colonocytes as a source of energy. (Usually, cells use sugar for energy, but colonocytes are some of the only cells we have that need butyrate to produce energy).
When we have more sugar than we need in our bloodstream, GLP-1 triggers our body to store the excess sugar away in our liver and muscles so that it can be used at a later time.
Additionally, GLP-1 is known to increase insulin release from the pancreas7.
As insulin increases, cells throughout the body start to take in sugar from the bloodstream, lowering blood sugar levels in the process.
Butyrate is also known to reduce inflammation in the gut by decreasing the amount of distress signals that are sent out from colonocytes (gut cells)4.
People with type 2 diabetes often have higher levels of gut inflammation which, in turn, causes a rise in blood sugar levels (immune cells require energy when on the hunt for potential invaders, and the body will boost sugar levels to help them). Decreasing inflammation can lead to decreased blood sugar levels4.
Butyrate is also known to support a tight gut barrier, but we’ll address that in more detail below.
If butyrate is so important, why can’t you just take a butyrate supplement and call it a day?
You could try and address some symptoms of type 2 diabetes by taking supplements that are specifically designed to deliver butyrate to the colon8.
However, such an approach would be similar to buying a box of nails and a hammer instead of hiring a carpenter—the butyrate delivered through the supplement may be temporarily effective, but it is only a temporary solution and one that fails to compensate for the many different roles that gut bacteria play.
Additionally, when bacteria produce butyrate, they do so while occupying many different locations in the gut. This means that butyrate can be moved closer to, or further from, the cells lining the gut depending on where the butyrate-producing bacteria are. By producing butyrate in various locations, the body can ensure that the right cell types get this precious nutrient.
Butyrate supplements, however, are hard-pressed to replicate these dynamics. Instead, they deliver the butyrate in an even and linear fashion that allows for any cell capable of using butyrate to do so.
As a result, the amount of butyrate available to the cells that need them, and the amount of butyrate that can bypass the gut and enter the body, can be significantly different when taking supplements as opposed to making the butyrate in-house with butyrate-producing bacteria.
This isn’t to say that taking butyrate supplements is inherently a bad thing, but it is important to note that butyrate supplements cannot fill the vacant roles left by missing bacteria.
Finding ways to replenish the bacteria that are so often missing in people with type 2 diabetes has several advantages. Restoring the missing bacteria may help reduce the leakiness of the gut while also providing an internal source of butyrate.
2. Regulating the mucin lining and preventing "leaky gut syndrome"
A gut that is described as “leaky” is one where the cell- and mucus-barrier that lines our intestine is more porous and less able to prevent molecules (or pathogens) from passing into the bloodstream.
The types of bacteria that are often missing in people with type 2 diabetes are known to help maintain a healthy gut barrier. They do this through several different mechanisms.
One way these bacteria contribute to the gut barrier is by helping to replenish the mucosal layer.
Akkermansia muciniphila, for example, is known to live in the mucosal layer and to feed on the mucus.
As it does this, it releases some molecules that are sensed by cells in the gut. These cells respond by producing more mucus. In this way, akkermansia muciniphila helps the gut keep a fresh and healthy mucus layer1,9.
Another way bacteria contributes to a healthy gut is by producing signaling molecules, like butyrate.
These signaling molecules promote several behaviors in the cells that form a tight barrier, one of which is to mechanically maintain the very tight connections between cells1.
Butyrate is known to trigger the production of tight-junction proteins in these barrier cells1.
When the cell-cell connection is tight, it is difficult for molecules, viruses, and bacteria to pass between the cells. Instead, they have to go through the cells. This gives the cell’s power to regulate what enters the body, and what does not.
In the absence of certain bacterial species, however, it becomes more difficult to maintain tight connections between these cells. Gaps form between them which allows various signaling molecules and other invaders to cross between cells and enter the body.
This can then lead to inflammation as immune cells detect a breach and respond with force1.
What specific strains of bacteria affect type 2 diabetes?
Details vary from study to study, likely because of differences in medication use, environment, diet, and exercise habits among participants in these studies. However, some groups of bacteria have been reliably shown to be protective.
Akkermansia muciniphila (WB-STR-0001) is one of them. As mentioned above, this strain of bacteria plays a critical role in supporting a healthy gut lining and in reducing gut inflammation, both of which favor healthy blood sugar levels.
Eubacterium hallii (WB-STR-0008) is a butyrate-producing bacteria. Many people with type 2 diabetes are deficient in this type of bacteria, which suggests that they may not be receiving as much butyrate. Given butyrate’s many beneficial effects on blood sugar regulation, replenishing butyrate-producing bacteria can be a big step towards managing type 2 diabetes.
Similarly, Clostridium butyricum (WB-STR-0006) and Clostridium beijerinckii (WB-STR-0005) are two more butyrate-producing bacteria that are often missing in people with type 2 diabetes. Many studies have focused on Clostridium butyricum and shown that replenishing this bacterial species can have clinical benefits for people with type 2 diabetes.
Bifidobacterium infantis 100 supports digestive health by aiding in the breakdown of complex carbohydrates that are otherwise difficult for the human body to digest. In this process, short-chain fatty acids similar to butyrate are produced. Loss of this bacterial species could thus lead to a decrease in beneficial signaling molecules.
Each of these strains of bacteria can be found in Pendulum Glucose Control.
Why are people with type 2 diabetes deficient in these strains?
There are many potential reasons why a person might start to lose these strains of bacteria.
We’ll cover some of the better-understood reasons here, but it is helpful to first cover a general truth about the gut microbiome:
It is a diverse and harsh ecosystem where bacteria must compete with one another for space, food, and other resources.
As a result, the species that survive in the gut are those that have found a competitive advantage, such as the ability to live deep inside a layer of mucus despite the lack of certain nutrients.
However, the specialization of some species leaves them vulnerable to environmental change. if they rely on fiber as their main food source, for example, they’ll have a hard time surviving if your diet changes and no longer includes fiber, especially soluble fiber.
With this in mind, here are some of the known factors that, if changed, can lead to deficiencies in certain strains of important bacterial species.
Diet & Nutrition
Changes in your diet and nutrition can lead to a decrease or loss of some bacterial species that are thought to protect you from type 2 diabetes.
This means that when the amount of fibrous foods in your diet (such as oats, nuts, and whole-grain foods) decreases, and the amount of high-fat foods increases (such as red-meats, fried foods, and cheese), you’re likely to start losing some beneficial bacteria1,4,5.
One reason for this change is that many types of bacteria that help protect us from type 2 diabetes rely on soluble fiber as an energy source.
When fiber levels are low or absent in the diet, these bacteria will struggle to survive and can be overrun by other, less beneficial species that do not rely on fiber as a food source.
This is one of the reasons it is generally recommended that a healthy eating plan is high in fiber.
Lack of exercise
Multiple studies have demonstrated a difference in the microbiome following exercise (both mild and exhaustive exercise).
In most studies, results suggest that people who exercise tend to have more beneficial bacteria in their microbiome relative to people who have a more stationary lifestyle10.
It’s not yet known, though, exactly how exercise causes this difference.
One suggestion is that physiological changes brought on by exercise—specifically changes in blood flow to the gut as well as an increase in the speed at which food moves through the gut—could lead to temporary changes in the gut microbiome environment.
When these momentary changes in the environment happen frequently enough, it can favor the survival of beneficial bacteria that thrive in those conditions10.
Another possibility is that exercise itself does not directly affect the gut microbiome but has an indirect effect that results from weight loss10.
In this scenario, exercise slowly leads to weight loss which in turn alters the gut microbiome.
A recurring challenge in this field of study is overcoming confusion around cause and effect. Is it weight loss and exercise that causes a change in the microbiome? Or does a change in the microbiome lead to weight loss?
At the moment, there’s not enough evidence to draw firm conclusions about how exercise alters the gut microbiome, but it’s likely related to a number of large and small physiological changes in the gut environment that ultimately make it easier for beneficial bacteria to survive.
Unlike most other factors, antibiotics have a clear cause-and-effect explanation for how they change the gut microbiome11.
Broadly speaking, antibiotics work by disrupting parts of bacteria that are critical to their survival; essentially throwing a wrench into the cellular machinery that helps them stay alive.
Most species of bacteria have their own unique set of cellular machinery, but they also tend to rely on some of the same core components.
It may help to think of differences between bacterial species as being similar to differences in models of cars. A pickup truck is fundamentally different from a sports car, but they both rely on wheels and an engine to move.
When antibiotics are designed to target these core components, they can be very effective but may also have collateral damage, especially in the gut.
Because of this, antibiotics can sometimes have a devastating effect on the gut microbiome that’s akin to a wildfire blazing through a forest, indiscriminately killing everything in its path. Many species will be affected, but the species that survive in the aftermath of it may be different compared to those who were present before.
Put simply, antibiotics can kill many bacteria in the body which is good when you have an infection, but can also lead to a loss of specific bacteria in the gut that help protect us from type 2 diabetes. These bacteria can be replenished, but that doesn’t always happen (likely owing to the combination of antibiotic use along with other factors listed here).
Chronic stress can have many different effects on our health and is often associated with changes in diet and exercise behavior.
And increases in chronic stress are associated with changes in the microbiome.
One possible reason for this is that stress causes the body to enter a survival mode when it anticipates tough times ahead. It knows it will need energy and responds by releasing an arsenal of hormones that help to boost blood sugar levels and increase immune cell activity.
Some of these hormones are released into the gut where they affect bacterial cell growth as well, acting to suppress growth and prevent activity in the gut. This is paired with altered blood flow and heightened inflammation.
Each of these responses alters the gut microbiome and, in turn, can change which type of bacteria are able to survive and thrive.
With age comes many physiological changes, including changes in the gut microbiome. As we age from infants to young adults, our gut microbiomes go through significant changes—likely due to changes in diet, exercise habits, and hormones13.
While the differences in the gut microbiomes are most prominent when comparing infants to adults, our gut microbiome can continue to evolve as we age out of young adulthood and into other phases of life.
It’s likely no secret that a person’s diet and exercise habits can change as they get older. Sometimes this is due to injuries or a lack of time. Stress, too, can play an important role in shaping both our habits and our microbiome.
Age can also lead to health conditions that require medication. These medications can have varied effects on the gut microenvironment, leading to new conditions that may favor one bacterial species over another.
In short, age brings with it a number of changing environmental factors that can then affect the gut microbiome.
Sleep patterns and a disrupted circadian rhythm
The circadian rhythm affects many, many aspects of our physiology, but is best known for its role in determining when we feel tired and when we feel awake.
Evidence suggests that the disruptions in the circadian rhythm may have several ways of affecting the gut microbiome14.
People who have conditions such as insomnia, chronic fatigue syndrome, and other conditions that alter the circadian rhythm were found to have significantly different microbiomes compared to their healthy counterparts. Those with circadian disruptions were shown to have decreased in several bacterial species, some of which are thought to be protective against type 2 diabetes.
The cause of this shift in the microbiome is not known. However, it may be related to the fact that circadian disruption is associated with higher levels of stress.
As mentioned earlier, stress can lead to inflammation and the release of numerous hormones in the gut that affect bacterial cell growth.
Genetics, environment, and more
We have limited our conversation here to a few of the main factors that have been studied. This list isn’t exhaustive, though, as there are several other influential factors that are believed to affect the gut microbiome.
The full list of factors is both diverse and growing, but they all share similar features:
Most things that affect your gut microbiome do so by changing the microenvironment of the gut (such as mutations in the DNA that cause different nutrients to be present in the gut mucus layer16), or else changing the types of bacteria that are introduced to the gut (new species might be introduced when traveling to foreign places).
In short, your gut microbiome is a complex environment and, like all environments, is always changing.
How can you increase these strains in your own microbiome?
Fortunately, there are steps you can take to increase the beneficial strains of bacteria in your gut microbiome.
Boosting the beneficial bacteria in your gut can be done through a combination of increasing the fiber, emphasizing soluble, content in your diet, forming routine exercise habits, and re-introducing key strains of bacteria through the use of probiotics.
The right nutrition
Bacteria strains that are believed to help protect us from type 2 diabetes can be nurtured and grown with a diet that includes soluble fiber-rich foods. This includes foods such as:
- Beans and legumes (black beans, kidney beans, pintos, chickpeas, white beans, and lentils)
- Whole fruits and vegetables
- Nuts such as walnuts, almonds, and peanuts
- Whole grain pasta, cereal, and oats
- Flax seeds
Adding in prebiotics, such as inulin, also help. Inulin is a type of complex carbohydrate that can promote beneficial bacteria in the gut15. Foods rich with inulin include:
Adding these foods to your diet can help ensure that there is a consistent food source for the beneficial bacteria. Be mindful to speak with your healthcare provider about adding these foods to your current eating plan. It’s important to add fiber slowly to your diet.
However, while the food source is important, it is also important to cultivate the gut microenvironment to be favorable for these bacteria.
Exercise and stress reduction
Exercise appears to play an important role in shaping the gut microbiome. People who exercise more tend to have more beneficial bacteria represented in their gut microbiome.
Exercise can be particularly helpful for people with prediabetes and type 2 diabetes for a number of reasons that go beyond the gut microbiome. It has been shown that routine exercise can help reduce blood A1C levels and lead to weight loss, both of which are associated with healthy blood sugar regulation.
Similarly, taking steps to reduce stress is likely to help encourage the growth of beneficial bacteria and ultimately reduce blood sugar levels.
Both stress and exercise have many trickle-down effects on the body, which makes it hard to nail down exactly if, or how these factors affect the gut microbiome. But it is clear that reducing stress and increasing exercise correlates with a healthy gut microenvironment and higher levels of beneficial bacteria.
The right probiotics
As mentioned earlier, the gut microbiome is a complex ecosystem that involves harsh competition between species. To help the species that protect us from type 2 diabetes survive, it’s important to give them a consistent food source (fiber for instance) and to make the environment as favorable to their survival as possible.
Forming an environment where these bacteria can thrive, however, may not be successful if the bacteria are already gone. This is where probiotics can be extremely helpful.
There are many probiotics in the market, each directed towards a specific set of conditions. With so many out there, it can be difficult to know what is the best probiotic supplement for people with type 2 diabetes.
Generally speaking, you should look for a probiotic that is backed by clinical evidence demonstrating efficacy in type 2 diabetes. This will likely include a combination of bacteria that help to increase butyrate production and reduce the leakiness of the gut.
Some probiotics will also include inulin as a starter food for the bacteria; this is to help the bacteria hit the ground running, so to speak.
Pendulum Glucose Control is one such probiotic. This medical probiotic provides 3 different species of bacteria that are known to boost butyrate levels and are often missing in people with type 2 diabetes. It also includes akkermansia muciniphila to help strengthen the gut barrier. Pendulum Glucose Control contains inulin as well to encourage rapid growth of these bacterial species.
In a double-blind clinical study, it was shown that people with type 2 diabetes taking metformin experienced a larger decrease in their blood A1C levels when taking Pendulum Glucose Control relative to people who had not taken it.17.
When we think about health and disease, the bacteria residing deep within our gut microbiome are often overlooked.
But the past few decades have revealed just how important the microbiome is. It’s a rich ecosystem teaming with life; and, like all ecosystems, it needs to be cared for.
We can care for our microbiome by forming routine exercise habits, reducing stress where possible, and by adding fiber and probiotics to our diet.
When we do these things, we favor the growth and survival of bacteria that help protect us from many different conditions, even type 2 diabetes.
Do gut bacteria affect blood sugar?
Yes, gut bacteria affect blood sugar levels through a number of indirect mechanisms that include the production of signaling molecules (such as butyrate) which can cause changes in sugar-regulating hormones (such as insulin or GLP-1).
How does gut bacteria affect insulin resistance?
Gut bacteria affect insulin resistance by influencing the following:
- Sugar regulating hormone levels (such as insulin, glucagon, and GLP-1)
- Gut barrier integrity
By influencing each of these, gut bacteria can affect how blood sugar levels and the body’s sensitivity to blood sugar levels. This can lead to changes in insulin resistance.
- Gurung, Manoj et al. “Role of gut microbiota in type 2 diabetes pathophysiology.” EBioMedicine vol. 51 (2020): 102590. doi:10.1016/j.ebiom.2019.11.051 https://www.thelancet.com/journals/ebiom/article/PIIS235239641930800-X/fulltext
Tai, Ningwen et al. “The role of gut microbiota in the development of type 1, type 2 diabetes mellitus and obesity.” Reviews in endocrine & metabolic disorders vol. 16,1 (2015): 55-65. doi:10.1007/s11154-015-9309-0 https://pubmed.ncbi.nlm.nih.gov/25619480/
Ortega, Miguel A et al. “Type 2 Diabetes Mellitus Associated with Obesity (Diabesity). The Central Role of Gut Microbiota and Its Translational Applications.” Nutrients vol. 12,9 2749. 9 Sep. 2020, doi:10.3390/nu12092749 https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7551493/
Liu, Hu et al. “Butyrate: A Double-Edged Sword for Health?.” Advances in nutrition (Bethesda, Md.) vol. 9,1 (2018): 21-29. doi:10.1093/advances/nmx009 https://pubmed.ncbi.nlm.nih.gov/29438462/ https://pubmed.ncbi.nlm.nih.gov/29438462/
Ojo, Omorogieva et al. “The Role of Dietary Fibre in Modulating Gut Microbiota Dysbiosis in Patients with Type 2 Diabetes: A Systematic Review and Meta-Analysis of Randomised Controlled Trials.” Nutrients vol. 12,11 3239. 23 Oct. 2020, doi:10.3390/nu12113239 https://pubmed.ncbi.nlm.nih.gov/33113929/
Madsen, Mette Simone Aae et al. “Metabolic and gut microbiome changes following GLP-1 or dual GLP-1/GLP-2 receptor agonist treatment in diet-induced obese mice.” Scientific reports vol. 9,1 15582. 30 Oct. 2019, doi:10.1038/s41598-019-52103-x https://www.nature.com/articles/s41598-019-52103-x
Gérard, Céline, and Hubert Vidal. “Impact of Gut Microbiota on Host Glycemic Control.” Frontiers in endocrinology vol. 10 29. 30 Jan. 2019, doi:10.3389/fendo.2019.00029 https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6363653/
Boets, Eef et al. “Systemic availability and metabolism of colonic-derived short-chain fatty acids in healthy subjects: a stable isotope study.” The Journal of physiology vol. 595,2 (2017): 541-555. doi:10.1113/JP272613 https://pubmed.ncbi.nlm.nih.gov/27510655/
Xu, Yu, et al. “Function of Akkermansia muciniphila in Obesity: Interactions With Lipid Metabolism, Immune Response and Gut Systems.” Frontiers in Microbiology, vol. 11, 2020, doi:10.3389/fmicb.2020.00219. https://www.frontiersin.org/articles/10.3389/fmicb.2020.00219/full
Bermon S;Petriz B;Kajėnienė A;Prestes J;Castell L;Franco OL; “The Microbiota: an Exercise Immunology Perspective.” Exercise Immunology Review, U.S. National Library of Medicine, pubmed.ncbi.nlm.nih.gov/25825908/. https://pubmed.ncbi.nlm.nih.gov/25825908/
Cully, Megan. “Antibiotics Alter the Gut Microbiome and Host Health.” Nature News, Nature Publishing Group, 17 June 2019, www.nature.com/articles/d42859-019-00019-x.
Karl, J Philip et al. “Effects of Psychological, Environmental and Physical Stressors on the Gut Microbiota.” Frontiers in microbiology vol. 9 2013. 11 Sep. 2018, doi:10.3389/fmicb.2018.02013 https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6143810/
Nagpal, Ravinder et al. “Gut microbiome and aging: Physiological and mechanistic insights.” Nutrition and healthy aging vol. 4,4 267-285. 15 Jun. 2018, doi:10.3233/NHA-170030 https://pubmed.ncbi.nlm.nih.gov/29951588/
Li, Yuanyuan, et al. “The Role of Microbiome in Insomnia, Circadian Disturbance and Depression.” Frontiers, Frontiers, 20 Nov. 2018, www.frontiersin.org/articles/10.3389/fpsyt.2018.00669/full.
- “Inulin Dietary Fiber with Functional and Health Attributes-A Review.” Taylor & Francis, www.tandfonline.com/doi/abs/10.1080/87559121003590664.
Kashyap, Purna C. et al. “Genetically Dictated Change in Host Mucus Carbohydrate Landscape Exerts a Diet-Dependent Effect on the Gut Microbiota.” Proceedings of the National Academy of Sciences of the United States of America 110.42 (2013): 17059–17064. PMC. https://pubmed.ncbi.nlm.nih.gov/24062455/