In the intricate world of the gut microbiome, where billions of tiny microorganisms coexist, scientists face the challenge of unraveling its complexity. Just as urban planners categorize neighborhoods into 'residential,' 'commercial,' or 'industrial' zones to unravel the dynamics of a city, scientists devised a method to simplify the intricacies of the gut microbiome.
In 2011, the concept of gut enterotypes (or gut types, as we call them in Tiny Health) was introduced for the first time . This novel approach proposed classifying the fully matured human gut microbiome into three distinct types then called – Bacteroides, Prevotella, and Ruminococcus – based on the dominant bacterial species within the community.
These gut types are different from baby gut types (used from 0 to 12 months old), since baby microbiomes are much less diverse than adult guts.
Keep reading to learn more about:
- The different gut types you may find in your Tiny Health report, and specific traits associated with each of them
- How common your gut type is
- Controversies surrounding this categorization system
Tiny Health adult gut types
We have categorized mature gut microbiomes into seven different types (which are different to baby gut types). Figure 1 shows the gut type distribution by age group. Scroll down to read the main characteristics of each of these.
The Bacteroides gut type
- A very common gut type in developed countries
- Dominated by species like Bacteroides, Phocaeicola, or Parabacteroides
- Often found in those who eat mostly animal-based foods
The Bacteroides gut type is common for all ages. In fact, this is the most common gut type for people in developed countries –. It’s often seen in those whose diet is high in animal protein and fats, with lower consumption of plant-based foods.
We see this gut type in an important percentage of Tiny Health users: 29% of adults and 21% of children and toddlers.
Compared to the Prevotella gut type, a good thing about the Bacteroides gut type is that it tends to have higher levels of Bifidobacterium species . In fact, babies with a gut type dominated by Bifidobacterium often transition to a Bacteroides gut type during toddlerhood . And compared to other gut types, the Bacteroides gut type has the highest potential to produce vitamin B12 and biotin .
Studies have shown that gut types respond differently to dietary interventions , . For example, while fiber-rich foods are beneficial for everyone, if trying to lose weight, the Bacteroides gut type may not benefit much from a fiber-rich diet , .
Researchers have identified two subtypes in the Bacteroides gut type, named Bact1 and Bact2. The Bact2 subtype has three main characteristics in terms of microbiome composition:
- Top species include Bacteroides fragilis, Phocaeicola vulgatus, and Parabacteroides distasonis
- Has a low diversity
- Has very low levels of Faecalibacterium prausnitzii 
This gut subtype is more often seen in people with obesity, insulin resistance, or inflammatory conditions such as inflammatory bowel disease and multiple sclerosis –.
The Prevotella gut type
- An uncommon gut type in developed countries
- Frequently dominated by Prevotella copri
- Often found in those that eat lots of plant fiber-rich foods
In developed countries, the Prevotella gut type is less common than the Bacteroides gut type in both little ones and grown ups , , , , , . We see this gut type in about 2-3% of Tiny Health users.
This gut type is often dominated by Prevotella copri, the most common Prevotella species in the human gut , . One important thing to note about P. copri is that different strains seem to have different food preferences. While some strains may be very good at digesting fibers in plant-based foods, others may not be so good , .
This variable nature of P. copri may explain the different and sometimes contradictory health associations that studies have found for the Prevotella gut type. Prevotella bacteria have been positively associated with:
- The production of beneficial short-chain fatty acids (SCFAs) , 
- Improved glucose metabolism , 
- An anti-inflammatory effect , 
- Effective weight loss or maintenance when on a high-fiber diet, especially with fibers found in cereal grains (whole-wheat, barley, oats, rye, etc.) , , 
- Lower cholesterol 
On the other hand, some studies have associated P. copri with:
- Inflammatory conditions , 
- Insulin resistance and glucose intolerance 
In any case, the Prevotella gut type is often seen in people with non-Western and/or fiber-rich diets , , , . That is, people whose diet is heavy in plant-based foods.
When compared to the other gut types, the Prevotella gut type has the highest potential to digest cellulose , an insoluble fiber found in plant-based foods.
The Ruminococcaceae gut type
- An uncommon gut type
- Dominated by species like Ruminococcus, Ruminiclostridium, and Faecalibacterium
In Western countries, the Ruminococcaceae gut type is less common than the Prevotella and Bacteroides gut type. Because of this, not many studies have explored how the Ruminococcaceae gut type responds to dietary or supplement interventions. We see this gut type in less than 0.5% of Tiny Health users.
Common bacteria that dominate this gut type are some Ruminococcus and Ruminiclostridium species, and Faecalibacterium bacteria. These bugs are good at breaking down fiber from carbohydrates to produce beneficial SCFAs –. Some species also feed on acetate produced by other bacteria, and transform it into another SCFA called butyrate.
Due to its ability to break down carbohydrates, the Ruminococcaceae gut type could make it easy to gain weight if eating too many carbs, due to increased nutrient availability and absorption.
The Lachnospiraceae gut type
- A common gut type in Western countries
- Dominated by species like Anaerostipes, Blautia, and Roseburia
Found in 35% of adults and about 50% of children and toddlers, the Lachnospiraceae gut type is the most common among Tiny Health users.
This gut type is often dominated by species like Anaerostipes, Blautia, and Roseburia. These bacteria are good at digesting plant fibers such as:
- Pectin 
And from these, Lachnospiraceae produce beneficial SCFAs like butyrate. That said, the ability to digest fiber and produce SCFAs varies depending on the species.
The Bifidobacterium gut type
- Seen in many toddlers and some children, characterized as immature gut community Rare in adults
- Dominated by beneficial Bifidobacterium species
Although a Bifidobacterium gut type is typical of babies, many toddlers and some children and adults can also have this gut type , , , . In Tiny Health users, we see this gut type in 0.3% of adults, 1.5% of children, and 16.5% of toddlers.
Compared to the Bacteroides and Prevotella gut type, the Bifidobacterium gut type has lower diversity , . From studies in toddlers and children, this gut type is considered to be more immature, and may not be able to properly digest complex carbohydrates typical of an adult diet. It’s unclear what this means for adults.
That said, this gut type is better than the other ones at producing branched-chain amino acids, which are essential for building protein in muscle cells .
In children and adults, common species that dominate this gut type are Bifidobacterium adolescentis and Bifidobacterium catenulatum .
If your toddler or child has this gut type, as they continue to grow, their gut microbiome will diversify and will likely transition to one of the other gut types that are typical of older children and adults . If you are an adult with a Bifidobacterium gut type, it’s a good idea to try to diversify the gut microbiome. Even if Bifidobacterium are beneficial bacteria that we like to see, for an adult microbiome it is not ideal that they dominate the gut.
The ‘Other’ gut type
- A gut type that doesn’t fit in the main categories
- This gut type is not dominated by any particular group of bacteria, so it’s very diverse
Instead of being dominated by Bacteroides, Prevotella, Ruminococcaceae, Lachnospiraceae, or Bifidobacterium, the ‘Other’ gut type has higher levels of a variety of species.
Having this gut type is not a bad thing; in fact, its high diversity may be beneficial for gut health. For Tiny Health users, this gut type is seen in 32% adults, 21% of children, and 8% of toddlers.
As microbiome research continues, we may be able to provide more insights about this gut type.
The Enterobacteriaceae gut type
- A rare gut type that a couple of studies identified in Asian populations
- Has high levels of unfriendly bacteria
- Could be temporary
The Enterobacteriaceae gut type has high levels of unfriendly bacteria such as:
This is not a common gut type for toddlers or adults but a couple of small studies have identified it in adult Asian populations , . One of these studies reported that compared to people with a Bacteroides or Prevotella gut type, those with an Enterobacteriaceae gut type ate a higher amount of red meat and had quicker transit times .
It’s also possible for this gut type to be the result of a recent gut infection or antibiotic treatment. Some of the top antibiotic-resistant bacteria are species of Escherichia and Klebsiella . If that’s the case, it should be possible for this gut type to shift to a different composition after recovery, potentially helped by probiotics or other supplements.
For Tiny Health users, this gut type is seen in 1% adults and 0.5% of children and toddlers.
More studies are needed to see how widespread this gut type is in different locations and whether it’s driven by specific dietary patterns or infections.
Some controversies on adult gut types
The topic of enterotypes or gut types is controversial among scientists. Depending on the method and dataset used, studies differ in the exact number of gut types defined. Many have described Bacteroides and Prevotella as the only two gut types , , , , while other studies have described three , , . In Tiny Health, we classified gut types into seven different groups because we believe this better reflects the differences we see in our users.
Besides, gut types aren’t as straightforward as blood types, where you fall into distinct categories (A, B, AB or O blood type). Unlike blood types, gut types can exhibit a degree of overlap. For example, when categorizing gut microbiomes into gut types, there are samples that fit neatly into a Bacteroides gut type, while others fall somewhere in between Bacteroides and Ruminococcaceae gut type. Your Tiny Health report will tell you which gut type your sample most resembles but it makes more sense to see these as a gradient in which different types can overlap –.
Finally, while gut types may be broadly correlated with the risk of a disease, the predicted response to a supplement, or specific diets, there's still a lot of variability within gut types that prevents a clear prediction. This is because of the dramatic differences between bacterial species and strains from the same taxonomic group. For example, as we saw for the Prevotella gut type, depending on the species or strain, this gut type can be associated with either positive or negative health aspects , , , .
For a more precise understanding of your gut microbiome health, we recommend looking into specific metrics available in your Tiny Health gut report. This will offer a more accurate picture of which key species are out of range or potentially contributing to any symptoms. Additionally, you’ll find the predicted potential of your whole gut microbiome to produce short-chain fatty acids, digest fiber, etc, rather than relying on composition alone.
Still, knowing your gut type can give you some general insights about your gut microbial community, and it can be fun to compare with family members. It can also give you hints on what aspects of your diet you may want to change or focus on. However, it’s crucial to keep in mind that the science behind gut types is still evolving, and that not all the characteristics associated with your gut type may necessarily apply to you.