Gut Microbiome And Stool Tests: Do I Need To Know What Lives In My Gut?

You may have noticed a recent influx of new products in the supermarket that make bold claims of improving gut health or being “gut-friendly.” These products and supplements often make miraculous promises to restore your gut microbiome, but more recently, there is a new holy grail: gut microbiome tests that claim to assess your individual gut microorganisms and help to diagnose imbalances. Sounds pretty good, right? All it takes is one stool sample to find the root cause of all your symptoms and gut struggles. Or at least that’s what is promised widely online.

Many of the nutrition and wellness trends are built on a grain of truth, which makes them believable and easily accepted as fact. However, taking scientific findings out of context, exaggerating or oversimplifying results, ultimately leads to misinformation. Nutritional studies are notoriously difficult to conduct due to the complexity of diet and food, human behaviour and other confounding variables which cannot be fully controlled. This means scientific findings from the nutrition field are often not well-suited to be translated into black and white statements or sexy clickbait headlines. Gut microbiome testing perfectly demonstrates this dilemma.

In this article, I deep dive into the research that looks into whether gut microbiome tests are worth your time and money.

What is the gut microbiome?

First off, what actually is the gut microbiome? In a nutshell, it is a fancy way of describing all the little critters that live in our gut. This includes different types of microorganisms including bacteria, archaea and even viruses. However, we are not just offering free housing to them; they play a very important role in our daily bodily functions, including supporting healthy digestion or fighting pathogens (the bad guys).

The presence of microorganisms was reported in the 17th century, but interest really took off with the development of new scientific methods, which show how complex and versatile our gut bugs really are - marking the beginning of the gut microbiome era[1].

Now, while we never have to feel alone ever again, knowing there are approximately 100 trillion microbes (weighing 2 kgs!!) living in our gut, it does not mean our gut bug friends remain the same over time. Just like our human friends, many factors influence who stays around or not.

The cold, hard truth: Do gut microbiome tests actually work?

Before you spend your hard-earned money and run off to collect poo samples to be tested, you should keep the following in mind:

1)         Your results will represent a snapshot of your current situation.

Your lifestyle, such as diet, physical activity, medication, genetics and even who you share a house with, has been shown to influence the gut microbiome[2]. This means the gut microbiome test results are just a reflection of the microorganisms present at the time of the test. For reference, dietary changes have previously shown some changes to the gut microbiome composition within a day[3]!

2)         We are all unique - even on a poo-ular level!

When we say, “you are one of a kind,” we mean it! This also applies to our highly individual and unique gut microbiome. This means there is no standard or definition for a ‘normal and/or healthy’ gut microbiome. Don’t expect your results to give you a statement on your health status like we see in blood test results, with clear ranges of what is considered healthy[4].

3)         Diversity lies in the eyes of the beholder.

We know a decreased gut microbiome diversity is associated with poorer health outcomes, and some commercial kits attempt to use a diversity rating to draw conclusions on the test subject’s wellbeing[5]. However, these ratings differ across test kits and have been found to report completely different findings for the same stool sample in a past study (good, average and low diversity!)[6].

4)         Staying mysterious.

This brings us to the wider underlying issue, the absence of a standard method of obtaining, storing and analysing the sample and interpreting the data, which significantly impacts results. It’s hard to tell from the websites of available kits how they do things, leaving us in the dark about how they produce their results[6].

5)         Are we testing your poo microbiome or your gut microbiome?
These gut microbiome testing companies use your poop to get a glimpse of what may be living in your gut, but it is really just a vehicle to get an indirect sample of the real thing? The bacteria identified in your stool is unlikely to be a full representation of what is actually present in your gut[8]. Some of these tests don’t even differentiate between alive or dead bacterial cells[7].

6)         Presenteeism - not even bacteria are safe!

Just like some work colleagues, specific bacteria being physically present does not mean the actual work is getting done. Particular bacterial strains have been reported to be crucial for gut health by producing short-chain fatty acids (SCFAs). SCFAs are metabolites formed by bacteria fermenting dietary fibre and taken up by our intestinal cells to help with immune responses and strengthen the gut barrier. Commercial tests, however, may confirm the presence of these bacterial families, but not how much, or if any, SCFA are actually produced[7].

What’s the verdict: should I do a gut microbiome test?

While it is fair to say that this is an extremely exciting and promising area of research, we need to acknowledge that it is still in its infancy. There is no consensus on whether and what role these tests will and can play in real-world medical use.

So, should you consider taking a gut microbiome test? If you’re looking for an explanation for any digestive symptoms or to gauge your level of health, we do not advise you to spend your money on gut microbiome testing. We need to wait for a better understanding and scientific evidence so that the information that is collected in these tests can actually be useful to you.

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This article was written by Melanie Bruckberger.

BSc (Biomedical Science)
Master of Human Nutrition
Currently undergoing Certificate III & IV in Fitness
TDC Intern

Whether it’s cellular processes, microorganisms, nutrition or the environment, Mel loves sharing scientific insights in a digestible way (pun intended!) and empowering people to make dietary and lifestyle-informed choices.

References

1.              Lewandowska-Pietruszka Z, Figlerowicz M, Mazur-Melewska K. The history of the intestinal microbiota and the gut-brain axis. Pathogens. 2022;11(12):1540.

2.              Schmidt TS, Raes J, Bork P. The human gut microbiome: from association to modulation. Cell. 2018;172(6):1198-215.

3.              Leeming ER, Johnson AJ, Spector TD, Le Roy CI. Effect of diet on the gut microbiota: rethinking intervention duration. Nutrients. 2019;11(12):2862.

4.              Ferranti EP, Dunbar SB, Dunlop AL, Corwin EJ. 20 things you didn’t know about the human gut microbiome. J Cardiovasc Nurs. 2014;29(6):479-81.

5.              Deng F, Li Y, Zhao J. The gut microbiome of healthy long-living people. Aging (Albany N Y). 2019;11(2):289.

6.              Rodriguez J, Cordaillat-Simmons M, Badalato N, Berger B, Breton H, de Lahondès R, et al. Microbiome testing in Europe: navigating analytical, ethical and regulatory challenges. Microbiome. 2024;12(1):258.

7.              Martin-Gallausiaux C, Marinelli L, Blottière HM, Larraufie P, Lapaque N. SCFA: mechanisms and functional importance in the gut. Proc Nutr Soc. 2021;80(1):37-49.