Gut Health and Fermented Foods: Separating Fact from Fiction

Metabolism & the Microbiome

Humans have between 10 trillion – 100 trillion microorganisms in their intestinal system.

This collection of intestinal microflora, known as the microbiome, contains approximately 100 more unique genes than our own (1). That means we contain more bacterial cells than we do human ones. Their presence in our gut makes us unique – our own metabolisms are an amalgamation of microbial and human traits (1).

Why does this matter?

Metabolism refers to the sum of all chemical reactions occurring in our body. Microbial metabolisms work very differently from our own, breaking down complex molecules to produce essential amino acids and vitamins.

The scientific community has long been aware of the importance of our gut bacteria and their relationship with our diets, with seminal nutrition studies being published in the 1990s. However, with new sequencing technologies, which allow us to explore the gut microbiome in more detail than ever before, we are now realising the transformative power of these little creatures on our health.

Recent studies published in the Nature science journal have found that age, gender, diet and even geographical location can influence what lives in your gut (2). They have also demonstrated that it is not necessarily the most abundant species (highest in number) that have the biggest impact on the molecular reactions occurring in your gut (2). Put simply, diversity matters.

Fig 1. This diagram illustrates the complexity of the relationship between the microbiome, our metabolism & our immune system. This is why we still have so much to learn about our gut and what is good for it! (I)

Diet & Diversity

In a small study on diet and the microbiome, scientists found that people who ate a more plant based diet had higher levels of Firmicutes in their gut, which break down complex carbohydrates (4). Firmicutes are aerobic bacteria, meaning they thrive on oxygen. An example of a Firmicute is Lactobacillus acidophilus, which is common in probiotics (3). This bacterium is an important part of a healthy microbiome however because it breaks down carbohydrates into sugar, it is associated with higher fat content in the gut. This means that unless your microbiome is out of balance (i.e. you’ve been on antibiotics or have gastrointestinal problems), you shouldn’t be consuming too much of this bacteria!

In contrast, those on an animal-based diet had a greater number of bile-tolerant organisms. Bile is produced by the liver and is essential for breaking down fat. The bile-tolerant organisms are predominately Bacteroides (4). There is still limited research on the relationship between commensal (good) bacteria and polyphenols, however a nutritional biochemistry study has suggested that increased consumption of polyphenols causes these bacteria to thrive (5). Polyphenols are naturally occurring compounds which can be found in plants, the skin of fruits and vegetables, tea leaves and coffee beans (5).

These differences in gut composition between plant and animal based diets actually reflected those of herbivorous and carnivorous animals (4)!

Whilst there is a lot more research still to be done, scientists are concluding that it is incredibly important to factor in the microbiome when considering overall health, diet and even mental health (such as depression, anxiety and stress) (2).

Probiotics & Fermented Foods – Fact or Fad?

Probiotics and fermented foods have become the buzz words of the health industry. But how much evidence is there that they actually help?

Most probiotics contain lactic acid producing bacteria. There is evidence that these bacteria are highly beneficial to your gut – they increase intestinal health, improve the immune response within the gut, increase availability of nutrients for absorption and can reduce lactose intolerance. However, when you’re taking oral probiotics, these bacteria need to survive the journey to your stomach, which can be a bit of a rough ride (6,7). Furthermore, they produce more sugar, which has been linked to an increased risk of obesity! Essentially, if your gut is already healthy and you’re eating a balanced diet, you don’t need to consume any more of these bacteria.

Yoghurt and fermented milks contain lots of lactobacilli, so they’re great for maintaining a healthy gut. All yoghurts must contain a minimum level of live cultures in order to be approved by Food Standards Australia and NZ, so simply choose brands which meet your desired levels of protein and sugar. Other fermented foods such as sauerkraut also contain high levels of lactic acid bacteria (Kehoe’s Kitchen has a wide range of sauerkraut). These are a different strain to those found in dairy products, so eating a little of both will increase diversity (7,8). 

Image 1. Electron micrograph of a strain of lactobacilli (lactic-acid) producing bacteria.

The popularity of kombucha has exploded recently. But there is still very little scientific research on its benefits. In contrast to other fermented foods, kombucha contains a combination of fungi and acetic-acid producing bacteria (hence its vinegary taste!) (9). It’s not clear how beneficial these particular microorganisms are, or whether they can actually survive and replicate in the gut.

This doesn’t mean you shouldn’t be drinking kombucha. But a varied diet, high in fruit and vegetables, lean protein and dairy or cultured dairy-free alternatives (such as Kehoe’s Kitchen Vegan “Cream Cheese” dip), is going to do a lot more for your gut health than relying on kombucha alone.

About the Author – Rachael Dodds

Rachael has been a Studio Pilates client since 2002 and started working at Studio Pilates HQ in 2013. She is passionate about the transformative impact these classes have had on her physical and mental wellbeing. She recently graduated with a Bachelor of Science (Microbiology) and Bachelor of Arts (Anthropology) from the University of Queensland. She was an elite track athlete for 9 years, representing Australia at the Athletics World Championships in 2011 and London 2012 Paralympic Games.

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