Getting to the guts of your health


gut microbiome stomach intestines bacteria

With mounting evidence supporting the influence of the gut microbiome, more people want to know how they can improve their gut health

Knowledge about the human gut microbiome has increased significantly over the past decade.

Yet while our understanding of gut health and the role of bacteria has come a long way, the gut microbiome is a complex community and there’s still a great deal we don’t know. There are also myriad differences from one person to the next that impact and interfere with an individual’s microbiome.

So, while many people now recognise the importance of maintaining good gut health, pharmacists can offer practical guidance.

Dr Vincent Ho, gastroenterologist and lecturer at Western Sydney University, explains, “We know a lot about the importance of gut bacteria from germ-free animals (most commonly mice) that are raised and maintained in a completely sterile environment. They are known to have a germ-free gut. However, they are much more susceptible than normal mice to infection by certain bacteria, viruses and parasites. For example, the introduction of just 10 Salmonella typhimurium bacteria is known to kill all germ-free mice within eight days of inoculation, whilst it takes 4700 Salmonella typhimurium bacteria to kill half a group of normal mice.

“The bacteria that are normally found in our gut, also known as ‘commensal bacteria’, are important in providing a barrier to protect against infections. They also help in the maturation of the immune system, particularly during early life.”

The impact of gut bacteria on health

Alongside producing nutrients, offering protection against pathogens, aiding absorption and assisting with digestion, the gut microbiota co-ordinates immune–neuroendocrine communication. So, it’s not too surprising that adverse changes to the rich landscape of the gut may impact this multidirectional dialogue and influence human health.

“A negative alteration in the gut microbiome is known as dysbiosis. Dysbiosis is linked to the development of many different diseases such as obesity, inflammatory bowel disease, type 1 diabetes mellitus, allergic disorders, autism, and colorectal cancer,” says Dr Ho.

“Notably these are associations and it is very difficult to establish causality. It is also easier to study the effects of dysbiosis in childhood diseases than in adult diseases where a whole range of environmental factors can impact the interpretation of results.”

Dr Ho tells the AJP, “The gut microbiome has taken on a special fascination with emerging evidence that it may be involved in the development of certain diseases. The idea that perhaps you could transmit some features of a person, such as their obesity or leanness, through their gut bacteria was first raised by an ingenious set of experiments carried out in Professor Jeff Gordon’s laboratory at Washington School of Medicine in St Louis, which is equipped to house germ-free mice.

Stool samples from human twins, where one was obese and the other lean, were transplanted into separate groups of germ-free mice. The mice receiving the microbes from the obese twin showed increased body fat and metabolic abnormalities”.

Meanwhile, the mice receiving microbes from the lean twin were leaner and more metabolically healthy.

“This idea of transmitting some of the physical properties of a person through their gut microbes was highly popularised by the media to a fascinated public. It became the source for many myths about special fad diets changing one’s gut microbiome and then leading to a distinct change in physical attributes. Much of the false belief about faecal transplants being able to cure all sorts of diseases has stemmed from this concept of transmitting physical attributes through the gut microbes.

“Diet pills and various probiotics that are purported to affect the gut microbiome have become fashionable. It’s important that pharmacists are aware of what is accurate information when it comes to claims that particular interventions affect the gut microbiome and improve health.”

Maintaining a healthy microbiome

Several factors are believed to influence the gut microbiome. However, environment and lifestyle are thought to have the biggest impact.

A 2018 study by Daphna Rothschild et al found that environmental influence could account for 20–25% of microbial differences. The main factors being diet, medication, such as statins, metformin and antibiotics, as well as body composition.

Another factor known to impact the microbiome is ageing. As the body ages it leads to a decline in microbial diversity, with beneficial strains of bacteria, such as bifidobacteria and lactobacilli, typically reducing.

Yet, while we can’t prevent ageing, we can be aware of the key features of a healthy gut and the factors within our control that influence the microbiome.

Dr Ho explains, “The three key features considered to be hallmarks of a healthy microbiome are diversity, stability and resilience. Diversity refers to how many different species of bacteria there are and how evenly distributed they are in the population. A healthy gut microbiome should be diverse, as low microbial diversity can be associated with disease.

“Secondly a healthy gut microbiome is stable and resistant to changes, such as fad diets for example. Finally, it should be resilient, which means that it returns to a healthy state after a disruption—such as following the use of antibiotics.”

In order to maintain healthy gut function Dr Ho advises it is sensible to avoid certain situations that can alter the microbiome and the mucosal immune system. This includes stressful events and eating an unbalanced diet. “A diet should be diverse and rich in fibre, which is known to be helpful for the gut microbiome.

“Exercise has been shown to be beneficial in promoting bacteria that produce a useful short-chain fatty acid called butyrate that is able to reduce inflammation and help nourish the cells lining the colon (known as colonocytes). Exercise can also encourage the growth of a particular type of bacteria (Akkermansia municiphilia), which promotes mucus secretion in the gut and can reduce inflammation in the colon and protect against metabolic syndrome.

“However, we must note that on occasion it may not be possible to avoid stresses to the gut microbiome. For example, some medications can adversely affect the gut microbiome with antibiotics considered the most important class of drugs to do this. Probiotics have been shown to shorten the duration of antibiotic-induced diarrhoea. In this case, pharmacists can play a helpful role by recommending a probiotic to assist a patient to more speedy recovery from antibiotic-induced diarrhoea.”

probiotic pills on white background

Advising on probiotics and prebiotics

The role of probiotics and prebiotics in strengthening and supporting gut health has gained much media attention over the past decade. As such, you may find yourself fielding a growing number of questions, particularly as some people may not understand the differences between the two.

“Probiotics very simply are live microbes that have beneficial qualities when they’re ingested. They can be found in live-cultured yoghurt and other fermented foods such as kombucha, kimchi and miso. It’s important to remember that not every single yoghurt or fermented food can be classified as a probiotic because they have to be shown to have a beneficial effect, usually from clinical studies,” explains Dr Ho.

He says where people are experiencing gut problems that don’t seem to improve, a probiotic supplement may be something to consider, but the type of probiotic will depend on their specific clinical situation.

According to Sniffen et al, when choosing an appropriate probiotic product for your patient, several factors must be considered. These are mode of therapy, disease specificity, in that one probiotic may be effective for one disease yet not in another, specific efficacy of strain, as well as product quality and formulation.
With regards to strain-disease efficacy, Sniffen et al found that several types of probiotics had strong evidence for the prevention of antibiotic-associated diarrhea; Saccharomyces boulardii I-745, a three-strain mixture (Lactobacillus acidophilus CL1285, L. casei Lbc80r, and L. rhamnosus CLR2) and L. casei DN114001. These probiotics should be used at a dose of 1–2 x 10 cfu/day, starting within 48 hours of the antibiotic and continued for 5–7 days after the antibiotic has been discontinued.

For paediatric acute diarrhoea, there was strong evidence found to support S. boulardii I-745, L. rhamnosus GG, L. reuteri 17938, L. acidophilus LB, L. casei DN114001, Bacillus clausii and an eight-strain mixture (VSL#3). The eight-strain mixture (VSL#3) was also strongly supported for the treatment of IBD, while L. plantarum 299v or B. infantis 35624 was better for IBS.

With regards to the role of prebiotics, Dr Ho explains, “These are compounds in food that act as a ‘fertiliser’ for good bacteria in the human gut. Prebiotics are found naturally in leeks, asparagus, wheat, oats and soybeans, among other foods.

“A key difference between probiotics and prebiotics is how they behave when ingested. Prebiotics are not digested or absorbed in the small intestine and arrive at the colon where they are fermented by bacteria. On the other hand, given that probiotics are live bacteria, some may find it difficult to survive the acidic and enzymatic conditions of the stomach and may not even reach the small intestine.

“As such, probiotics should be ‘administered in adequate amounts’ allowing for enough bacteria to arrive at the colon to exert beneficial health effects. This is the reason why you see commercial probiotic capsules often containing many billions of colony forming units. The concentrations of bacteria exceed what is normally found in fermented foods and this high starting concentration is thought to provide the best chance for the bacteria to survive the stomach to colonise in the gut.”

*For more on this topic, including a look at supporting children’s gut health, and the impact of medicines on the gut microbiome, see our April print magazine or eMagazine.

Information sources:

Sniffen JC, et al. Choosing an appropriate probiotic product for your patient: an evidence-based practical guide. PLoS One. 2018;13(12):e0209205. doi: 10.1371/journal.pone.0209205.

Dominguez-Bello MG, et al. Partial restoration of the microbiota of cesarean-born infants via vaginal microbial transfer. Nat Med. 2016;22(3):250-3. doi: 10.1038/nm.4039. Rothschild D, et al. Environment dominates over host genetics in shaping human gut microbiota. Nature. 2018;555(7695):210-5. doi: 10.1038/nature25973.

Vich Vila A, et al. Impact of commonly used drugs on the composition and metabolic function of the gut microbiota. Nat Commun. 2020;11:362. doi: 10.1038/s41467-019-14177-z.

Shao Y, et al. Stunted microbiota and opportunistic pathogen colonization in caesarean-section birth. Nature. 2019;574(7776): 117‑21. doi: 10.1038/s41586-019-1560-1.

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