What is an enterotype?
Recent research suggests that the human microbiome can be assigned to three main groups – so-called enterotypes. Intestinal bacteria develop – depending on the enterotype – stable, clearly different clusters with typical metabolic properties.
The three enterotypes are thought to consist of, or be dominated by, the following bacteria:
- Enterotype 1 is enriched in Bacteroides and the co-occurring Parabacteroides.
- Enterotype 2 is enriched in Prevotella which co-occurs with Desulfovibrio.
- Enterotype 3 is the most common enterotype and is distinguished on the basis of enrichment in the levels of Ruminococcus and the co-occurring Akkermansia bacteria.
These categories, named ‘‘enterotypes”, were reported originally as ‘‘densely populated areas in a multidimensional space of community composition,” which means that they are not sharply delimited as human blood types (Cheng & Ning, 2017).
However, with more recent studies focusing on the stratification of human gut microbiome, it has been noticed that the number of enterotypes varies when different methods are employed even on the same samples. It appears some researches believe that there may only be two real enterotypes.
What Effects Enterotype?
It has been demonstrated that enterotypes are independent of sex or age and remain stable for years and it is thought that long-term dietary patterns are important contributors to the enterotype of an individual. Although short-term diet adjustment might not be able to change the enterotype, the long-term diet has been observed to significantly associate with the enterotype patterns (Cheng & Ning, 2017). A study by Liu et al.  has revealed that even after half a year, the enterotypes of the Chinese individuals can be reverted after the subjects shift back to their routine diets. Therefore, the impact of long-term dietary shift needs to be further investigated.
Other research has suggested that the administration of antibiotics, and age, may indeed influence our enterotype.
To make it even more confusing, some research demonstrates that for some healthy subjects, enterotype can vary widely and continuously over time.
Interestingly enterotypes are distinctly distributed over the BSS scores: the Prevotella (P) enterotype is more abundant in subjects with loose stool while the Ruminococcaceae-Bacteroides (RB) enterotype completely dominates the harder stool samples (Vandeputte et al., 2015).
It also appears nutrient status/intake may influence the enterotype (hence long term dietary habits are connected):
“The types of vitamins whose intake levels were found to be associated with the enterotypes were vitamin A, including retinol and carotene, vitamin C, and vitamin E. All of these vitamins have antioxidant properties, and influence immune function by strengthening epithelial barriers and cellular immune responses. Moreover, a study with vitamin A-deficient mice revealed that vitamin A can modulate the composition of gut microbiota, and in turn affect the differentiation of pro-inflammatory Th17 cells. Thus, our data suggest that dietary vitamin intakes may partially contribute to particular configurations of the gut microbiota, and therefore, host immune phenotypes may differ according to the host’s enterotype.”
Another interesting quote is:
“In the present study, enterotype 2 was associated with diets higher in fruit and egg food items compared to enterotype 1. For energy-adjusted nutrient intakes, enterotype 2 had significantly higher levels of dietary fiber, minerals (potassium and iron), and vitamins (vitamin A, vitamin C, vitamin E, folate, carotene, and retinol) than enterotype 1.
No significant associations were noted between enterotypes and macronutrients such as protein, fat, and carbohydrate. In the present study, enterotype 2 was associated with diets higher in fruit and egg food items compared to enterotype 1. For energy-adjusted nutrient intakes, enterotype 2 had significantly higher levels of dietary fiber, minerals (potassium and iron), and vitamins (vitamin A, vitamin C, vitamin E, folate, carotene, and retinol) than enterotype 1.
No significant associations were noted between enterotypes and macronutrients such as protein, fat, and carbohydrate.’
Why Is Enterotype Important?
The described enterotypes show significantly differing metabolic performance.
- Enterotype 1 is optimally adjusted to the utilisation of fat, fatty acids, protein and amino acids.
- Enterotype 2 is optimally adjusted to metabolise carbohydrates, and cannot metabolise fat and protein adequately. Enterotype 2 has been found more frequently in strict vegetarians. Diet-independent lower LDL-c levels in subjects from Prevotella than in other enterotypes suggest that a protective bacterial cluster may be driving this association.
- Enterotype 3 is capable of degrading mucins.
The enterotypes also influence the absorption of minerals like sodium, potassium, calcium or iron.
Enterotypes 1 and 2 have been shown to be enriched in the biosynthesis of different vitamins: biotin, riboflavin, pantothenate and ascorbate in the former, and thiamine and folate in the latter.
Enterotypes seem to be useful to understand the impact of daily diet exposure on cardiometabolic risk factors.
A study has shown that individuals with an enterotype characterized by enriched proportions of Prevotella have significantly higher plasma concentration of trimethylamine-Noxide (TMAO), a proatherogenic metabolite, than individuals with a Bacteroides enterotype, indicating that enterotypes affect the host (us) (Roager et al., 2014).
Can You Change Enterotype?
Many studies have shown that gut microbiome composition, in healthy adults, is relatively stable and doesn’t change much over long time periods. This suggests a generally stable ecosystem, and enterotype stability. There are, of course, important exceptions to this.
In one study, over 6 months, 16% of individuals switched enterotype between visits suggesting that, at least for these individuals, gut microbiome composition can be relatively fluid.
To understand this we need to understand the response of the gut microbiome to different perturbations – mainly antibiotics, dietary changes and feral microbiota transplants.
Dietary changes, which cause considerably less perturbation to the gut microbiome, may thus be better suited for investigating the resilience of the microbiome.
Significant changes in gut microbiome composition have been observed within four days and could cause an enterotype shift.
However, an important finding is that after about ten days, the enterotype appeared to return to the original one, suggesting a tendency of recovering the original state.
This results suggest that there are limitations on how much an individual’s microbiome may be influenced by short-term dietary changes and support the idea of enterotype resilience.
But what about more long term dietary changes? Do they have a more profound effect?
Dietary modulation over the period of a year have been shown to have a strong impact on the Bacteroidetes/Firmicutes ratio, potentially leading to enterotype switches.
As enterotypes were generally stable over time and no follow-up studies exist for the long-term interventions, no approximation of their resilience either in terms of overall community resemblance or enterotype assignmentcan be derived from the available data.
Instead of discrete enterotypes, this kind of distribution is deemed as a continuum changing from Bacteroides- driven to Prevotella-driven microbiota types
Enterotype has remained a controversial concept as to whether human gut microbiome can be clustered into different types or just fall into a continuous gradient.
Testing Your Microbiome
You can assess your enterotype via stool testing. Click here to order a stool test from Healthpath, and receive a personalised report of your results.
- Cheng & Ning, Stereotypes About Enterotype: the Old and New Ideas: click here
- Vandeputte et al., 2015, Stool consistency is strongly associated with gut microbiota richness and composition, enterotypes and bacterial growth rates: click here
- Roager et al., 2014, Microbial Enterotypes, Inferred by the Prevotella-to-Bacteroides Ratio, Remained Stable during a 6-Month Randomized Controlled Diet Intervention with the New Nordic Diet: click here