Your gut bacteria: The good, the bad & the jack of all trades

Author: Dr Paula Smith-Brown (APD, PhD)

24 February 2021 Education Health Conditions Latest Science Nutrition
Gut bacteria

Many of us may be familiar with the idea of "good" and "bad" bacteria but the truth is, it is not always that clear cut.

When we talk about “good bacteria” we might be thinking of the limited number of probiotic species found within supplements or fermented foods. However, our bodies are in fact home to many more species that together form a community of microbes known as our microbiome. Our health depends on the balance between these species, which is not solely influenced by the bacteria themselves but by what we feed them.

How bacteria influence your health

Generally, bacteria that turn the fibre we eat into beneficial compounds, such as Short Chain Fatty Acids, are associated with improved wellbeing. One example of this is the species Faecalibacterium prausnitzii which at high levels has been linked to many health benefits including reduced levels of belly fat and better blood sugar control,1 while low levels or an absence of this species has been seen in patients with inflammatory bowel diseases2 or asthma3.

In contrast, some bacteria prefer to consume protein and can produce compounds often associated with poor health outcomes. For example, a species known as Eggerthella lenta has been linked with higher levels of belly fat and worse blood sugar control,1 and high levels have been seen in patients with asthma3.

See how your gut bacteria may be influencing your health with Insight™ gut microbiome analysis.

How bacteria adapt to your lifestyle

Of course, nothing in life is ever that simple and we can’t label every bacterial species as either “good” or “bad”.

Some species can use both fibre and protein as fuel sources.  This means that the compounds these species produce and how they impact your health will largely depend on your diet and lifestyle.

A good example of this is a species known as Prevotella copri which has been linked to both positive and negative health outcomes. Some studies have shown high levels of Prevotella copri in people with diabetes4,5 and arthritis, including rheumatoid arthritis6 and ankylosing spondylitis,7 while other studies have shown reduced levels of Prevotella copri in people with Parkinson’s disease8. A recent study out of the UK reported that having Prevotella copri species within your microbiome was associated with 12.5% less belly fat,1 which not only affects your figure but is a risk factor for heart disease, diabetes and Alzheimer’s dementia.

Understanding your bacteria’s ever-changing role

To understand these conflicting results, we need to consider how Prevotella copri functions depends on our diet and lifestyle choices. Prevotella copri is a species that is commonly found in non-western populations and appears mismatched to the dramatic shifts in diet and lifestyle that have occurred in the Western world over the last 100 years. It is found in over 95% of people from non-western countries9 and when combined with a minimally processed, high fibre diet it will produce beneficial Short Chain Fatty Acids that can help support health. However, in the Western world, Prevotella copri is found less frequently, in fewer than 30% of individuals9.

Combining a Prevotella copri containing microbiome with a Western diet and lifestyle can be a risk to health.

Western-style diets are low in fibre which encourages Prevotella copri to use protein instead of fibre. This results in the generation of compounds known as Branch Chain Amino Acids (BCAAs) which are used by our muscle tissue. Unfortunately, a more Western “couch potato” lifestyle reduces the amount of muscle tissue available to deal with these extra BCAAs. If the level of BCAAs produced by the microbiome is higher than the muscle’s ability to break them down it leads to a build-up of toxic compounds which can damage our health10.

What can you do?

Prevotella copri is a well-studied example of a bacterial species that can play different roles in our health depending on our diet and lifestyle choices. However, many other bacterial species can also use multiple fuel sources and will produce different compounds based on the fuel they are provided.

Those lucky enough not to have lost Prevotella copri from their microbiome should understand that this can make them more susceptible to the negative impacts of a Western-style, low fibre diet or a “couch potato” lifestyle. However,  the good news is that a Prevotella copri containing microbiome can maximise the health benefits of positive lifestyle choices, such as choosing a high fibre diet and maintaining muscle mass through regular activity. These are both easy ways to promote the production of beneficial compounds by your gut microbiome.

Testing your microbiome can help you understand the balance of bacteria within your body as well as inform the best diet to suit your unique microbiome and health needs. So, before you jump to categorising the microorganisms that live in your gut as “good” and “bad” you should first look at what’s there and how you can maximise their potential!

Measure and track your gut bacteria with Insight™ gut microbiome analysis.

This microbiome test is not intended to be used to diagnose or treat medical conditions. A full disclaimer is available here



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