Why does microbiome diversity matter?

When we talk about the concept of ‘gut health’ in terms of consumer wellbeing, it can be difficult for formulators to picture what this looks like in practice. Most often, a ‘healthy gut’ refers to the balance of bacteria in the gut, and whether that balance is favourable.

Each year in June, World Microbiome Day provides an opportunity for everyone, from consumers to product developers, to build a stronger knowledge of the gut microbiome. The awareness day highlights some of the incredible science and technology that guides today’s health and wellness sector.

The gut microbiome is the community of bacteria in the gastrointestinal tract, which can be beneficial to the human host. Among the kinds found – estimated to be around 1000[1] different species – there are types of gut bacteria that are particularly beneficial, known as ‘good bacteria’. There are also kinds of bacteria that are less useful to the body, some are benign and others can be harmful!

It is often associated that having balance favouring ‘good bacteria’ over other kinds can have a positive influence on health and notably, it is understood that having a diverse collection of bacteria to support the function of human physiological systems is important. Better understanding of the gut microbiome and its interplay with other areas, such as the immune system, brain function and cognition, has led the innovation charge for a number of dietary supplements, such as prebiotic ingredient Bimuno® GOS, a dietary fibre designed to boost a specific kind of good bacteria, bifidobacteria.

Interestingly, the diversity of a gut microbiome can be a predictor of general health – particularly the ratio of two particular bacteria types, firmicutes to bacteroidetes. However, the environment and diet can both play a major role in gut microbiome diversity[2].

What are the benefits of a diverse gut microbiome?

Bacterial diversity is one way that gut health is monitored and addressed. In order to understand the benefits of diversity in the gut microbiome, first we need to understand the impact an imbalanced gut microbiome can have. A lack of diversity can lead to proliferation of unhelpful or harmful bacteria, known as dysbiosis.

Dysbiosis of the gut microbiome can lead to compositional changes that can affect the functionality of the gut microbiome. These effects have been associated with some diseases and gastrointestinal conditions.

Higher diversity of species in the gut microbiome is recorded in populations and communities that reflect the hunter-gatherer lifestyle[3] and diet of the Western world’s ancestors. This diversity is thought to provide greater stability and flexibility to withstand pathogens. Higher microbial diversity is often associated with a gut microbiome that is more resilient. A gut microbiome that has been negatively impacted in terms of microbial composition can return to equilibrium after physical, chemical and microbial influences, further underlining the connections between lifestyle, diet and health.

Defining a ‘healthy gut microbiome’ is complex, because the gut microbiome is as unique as a fingerprint and composition varies from one person to another. However, patterns have been recognised between the gut microbiome and immune function, as well as brain and cognitive health, nerve system function and nutrient acquisition.

Understanding changes in gut bacteria diversity in connection to specific biomarkers provides greater clarity on cause and effect, which in turns helps to indicate and benchmark a healthy gut microbiome[4].

What is happening to gut microbiome diversity?

The microbiome’s composition isn’t fixed – as lifestyles and consumption habits have changed throughout time, our microbial communities have adapted and changed to the nutrients available. We can even see evidence of these changes today.

For example, the Hadza people of Tanzania maintain a hunter-gatherer lifestyle, reminiscent of our ancestors. Because of this, they have a high dietary diversity, eating approximately 600 species of plants and animals throughout the year. This results in high gut microbiome diversity that differs significantly from contemporary Western or urban diets. Additionally, the Hadza people have no exposure to commercial antibiotics and pesticides.

When tackling the public health issue of decreasing intestinal diversity[5], aspects of Western culture and lifestyles must be considered. For instance, it may not be that a full 600 species a year are recommended, but rather a small incremental increase in the types of plants consumed weekly.

We can also see lifestyle changes in rural populations such as in the Himalayas where farming industrialisation has changed the gut microbiome composition in those communities. Although a change in diversity was not reported, the change in composition suggests that the industrialisation of lifestyles is what begins the initial change in gut microbiome composition to later cause a fall in gut microbial diversity[6].

In a further example, in a cohort of people who immigrated to the United States, dietary variation was a contributor to the gut microbiome changes observed. There was a significant shift in the dominant types of bacteria in the microbiome, away from an abundance of prevotella and towards a greater bacteroides proportion. Displacement of native bacteria with European and American bacteria occurred at varying rates – and even short residence in the United States reduced bacterial diversity and changed the gut microbiome composition[7].

These recorded changes are likely due to multiple factors associated with Western lifestyles, such as stress, altered exercise patterns and antibiotic exposure, as well as dietary changes. The lack of dietary fibre causes a reduction in prevotella and the enzymes required to break down dietary fibre. Additionally, dietary patterns in Western countries have become less abundant in fibre. This provides fewer carbohydrates for microbes to feed on in the gut, which has led to a reduction in some beneficial bacteria over several generations[8].

What are the ways to support diversity in the gut microbiome?

From birth (and perhaps even earlier), various factors are known to affect the development of the gut microbiome and its diversity later in life. Exposure to microorganisms and reducing interruptions to the developing gut microbiome in the first 3 years of life is important for building diversity in the gut microbiome[9].

There may be a decrease in gut microbiome diversity in Western countries, however there are lifestyle choices that can be made to help our diversity thrive:

  1. Breastmilk bacteria influence the development of the gut microbiome in infants and there is a continued benefit after the introduction of solid food. Breastfeeding is associated with bacteria that decrease the risk of allergy development in infants. This highlights the importance of breastfeeding and the early development of the gut microbiome[10].
  2. Exercise is associated with positive effects on gut microbiome diversity. Cardiorespiratory fitness is linked with better microbial diversity, suggesting that both fitness and microbial diversity are benefits gained from exercise. The improvement is thought to be caused by the resulting increase in abundance of butyrate producing bacteria from higher levels of physical activity[11].
  3. Dietary intake is one of the main environmental factors that can shape the intestinal microbial community. The type, amount and balance of the three macronutrients – carbohydrates, protein and fat – have a large impact on the composition of the gut microbiome. A diet high in plant-based foods, particularly complex carbohydrates, and lower in fat and animal proteins, is protective against inflammation and leads to a preferable composition of bacteria in the gut[12].
  4. The changes in food manufacturing due to industrialisation, alongside pressures for greater food production, has led to a decreased agrobiodiversity. As a result, dietary diversity has decreased over generations. Dietary diversity contributes to feeding a diverse microbial community in the gut[13]. Increasing the variety of foods included in a weekly dietary pattern can feed and promote a greater diversity of beneficial microbes in the gut.
  5. Supplementing diet with prebiotic and probiotic foods can improve gut microbiome composition and, in some cases, using supplements is recommended, where prebiotics cannot be obtained from diet alone. Probiotics are live microorganisms consumed for their health promoting benefits and supplementing a diet with probiotics after a course of antibiotics has been reported to reduce the proliferation of opportunistic pathogens in the gut and restore diversity[14].
  6. Prebiotics, defined as ‘a substrate that is selectively utilised by host microorganisms conferring a health benefit’[15], can promote growth of beneficial bacteria. Consuming a variety of foods in a dietary pattern that is rich in complex carbohydrates and plant-based foods can provide naturally occurring prebiotics. However, there is notable a fibre gap; in UK adults, while the recommended intake of fibre[16] is 30g, the average amount consumed by an individual is just 20g. In cases where it may be difficult for people to increase their fibre intake significantly, a prebiotic supplement could be recommended, such as Bimunoâ.

The key understanding, and perhaps the next significant step-change in consumer understanding of the complexities of gut health, is recognising the influence and benefits of a diverse microbiome. While the science behind it is still relatively new, diversity is understood to be hugely important in microbial communities for general good health.

[1] https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4262072/

[2] https://www.mdpi.com/2072-6643/11/7/1613

[3] https://www.nature.com/articles/ncomms4654

[4] https://academic.oup.com/jn/article/149/11/1882/5542976

[5] https://www.sciencedirect.com/science/article/pii/S0960982215006144

[6] https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6237292/

[7] https://www.sciencedirect.com/science/article/pii/S0092867418313825

[8] https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4850918/

[9] https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5032909/

[10] https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5710346/

[11] https://www.researchgate.net/profile/Muhammad_Umar_Sohail/publication/334961464_Impact_of_Physical_Exercise_on_Gut_Microbiome_Inflammation_and_the_Pathobiology_of_Metabolic_Disorders/links/5d4e6ef792851cd046afee7c/Impact-of-Physical-Exercise-on-Gut-Microbiome-Inflammation-and-the-Pathobiology-of-Metabolic-Disorders.pdf

[12] https://www.sciencedirect.com/science/article/pii/S0014579314002543

[13] https://www.sciencedirect.com/science/article/pii/S2212877816000387

[14] https://www.tandfonline.com/doi/full/10.1080/19490976.2016.1138197

[15] https://isappscience.org/for-scientists/resources/prebiotics/

[16] https://www.nutrition.org.uk/healthy-sustainable-diets/starchy-foods-sugar-and-fibre/fibre/?level=Health%20professional