You’ve probably noticed the explosion of information about gut health and the microbiome across the internet. Maybe you’re tempted to learn more about your gut health through at-home testing kits. But what do we really know about gut health tests? And more importantly, can they help you make decisions that will benefit your overall health?
What Is the Gut and the Microbiome?
Before delving into gut health tests, let’s define the gut and the microbiome. First, the “gut” refers to your entire digestive system, starting at your mouth and ending at your anus. However, when we talk about the gut microbiome, we refer to the colonies of tiny organisms called microbes that predominantly live in your small and large intestine.
Your gut is home to trillions of microbes, including bacteria, viruses, fungi, and other microorganisms. There are approximately the same bacterial cells as human cells in the human body!. In most healthy people, bacterial species dominate the microbiome, each with a specific function in your body. These microbes are working hard to keep you healthy 24/7. But, to maintain your health and well-being, they need an environment that allows them to flourish.
The foundation of your microbiome is built very early on, back when you were still in the womb. Microorganism colonization continues during birth and will be different if you were born vaginally or by cesarean section. Other factors influence your gut microbiome after birth, including genetics, feeding practices, the environment, and medication exposure.
What Does It Mean to Have a Healthy Microbiome?
Your microbiome is unique to you alone (save this point – it’s crucial to understand some limitations of gut health testing that we’ll get into below). In the Earth Microbiome Project, researchers combined data from healthy people worldwide. They found a vast spectrum of healthy and beautifully illustrated just how individual the microbiome is.
This large variation between individuals explains why defining a “healthy” microbiome is so difficult. But, we do know that diversity is a good thing. The more species diversity in your gut, the healthier your microbiome tends to be. Lower microbial diversity is commonly associated with type 2 diabetes, Celiac disease, inflammatory bowel disease, atopic eczema, and other conditions.
Defining a single microbiome composition that is considered the most desirable is also challenging because the microbiome is dynamic; it constantly changes and adapts based on your exposures throughout life.
How Does Your Microbiome Affect Your Overall Health?
The microbiome is integral to many fascinating pathways in the body, the depth of which we are only just starting to uncover.
The gut is sometimes called the “second brain” because it has its own nervous system (the enteric nervous system). These nerve cells communicate with your central nervous system (your brain), which likely impacts your mood, cognition, memory, and learning.
In addition to having its own nervous system, your gut is home to part of your immune system. Together, your gut and immune system identify and defend against pathogens while learning to tolerate beneficial microbes.
The gut also produces compounds called short-chain fatty acids (SCFAs). When you eat non-digestible dietary fibers, specific bacteria in the gut use them as an energy source. These fibers metabolize into SCFAs, which help regulate energy balance, glucose and fat metabolism, and inflammation.
Should You Test Your Gut Health?
There’s no question that the microbiome is crucial to your health. But can you learn anything actionable from testing your gut health?
There are gut health testing claims that many diseases result from gut microbiome imbalances. While this may be true, we aren’t entirely sure of the direction of these associations yet. Take Crohn’s disease as an example: people with Crohn’s tend to have dysbiosis. This means they have lower levels of beneficial bacteria and higher levels of harmful bacteria. What we don’t know, however, is whether or not that imbalance caused their Crohn’s or the imbalance happened as a consequence of Crohn’s.
Furthermore, research on the gut microbiome and disease associations relies on clinically available testing methods, not those available through at-home testing. If you are concerned about your health and the potential impact of your microbiome, it’s best to see your doctor.
What Are the Limitations of Gut Health Testing?
Unfortunately, gut health testing doesn’t have the accuracy and reliability needed to make clinical decisions. This is especially true of the methods used for at-home testing. If you are considering testing your gut health, there are several limitations to be aware of.
There Is No Defined Reference Range
Remember when we said that your gut microbiome is unique to you alone? This is where that point matters. Given the individuality of the microbiome, there isn’t a defined reference range for microbes in your gut that we can apply to everyone.
So, your results are compared to something, but is that range relevant for you? There’s no way to know. Plus, reference ranges will differ from company to company – you might have something flagged as abnormal from one company but listed as normal from another. Confusing, right?
You Only Get a Snapshot of One Point in Time
Another important point from earlier: your microbiome is dynamic and constantly adapting. Therefore, your gut health test tells you about your microbiome at only one moment. It doesn’t give you any insight into what is happening to your gut health over time.
Stool Samples Don’t Give the Full Picture of Your Microbiome
At-home testing relies on sampling procedures that you can easily do at home. Test kits use stool almost exclusively because it is convenient and accessible. The problem is that your stool doesn’t tell you the whole story.
For example, some microbes stick to the mucus in your small intestine, meaning they never make it into your stool. Microbial growth also changes as you pass from the small intestine into the large intestine and move throughout the different sections of the large intestine. Active water reabsorption and bacterial fermentation in the large intestine affect the types of microbes produced.
Therefore, the microbes in your stool may not accurately reflect those colonizing the rest of your gut.
We Don’t Have Guidelines to Interpret Results
You will likely receive some additional information or explanations along with your results. Many companies and doctors attempt to interpret your results into real-world, actionable recommendations. While this may sound appealing, we don’t have a standardized, evidence-based method to go from results to recommendations.
Based on test results, some companies and doctors give a list of foods to avoid. However, there is no scientific backing to these recommendations because we have no data to support the avoidance of foods from gut health testing. You may inadvertently end up on an overly restrictive diet, which could have its own associated health consequences.
So, What Can You Learn from an At-Home Gut Health Test?
Gut health is a fascinating area of research, and there are some exciting prospects about what we could learn about disease pathology from the microbiome. However, research is still in its infancy, so it’s essential to understand the limitations.
Clinically, researchers and health professionals have proposed microbiome testing as a screening tool for colorectal cancer and inflammatory bowel disease. However, it’s important to note that the testing methods used in these areas are not the same as those used for at-home testing.
An at-home gut health test is informational, at best. It’s not diagnostic, and it may not be entirely accurate. You might learn something interesting about the overall diversity of your microbiome. However, it’s crucial to interpret the results in the context of the limitations. Given the problems with defining reference ranges, testing your gut health over time and comparing yourself to yourself will give you a better understanding than a single test.
What to Know if You Choose to Test Your Gut Health
If you are interested in at-home gut health testing, do your research before committing to a company. Remember that gut health tests do not replace visits to your doctor, and the results are not diagnostic.
Here is what to expect from an at-home gut health test:
- Choose the company. Be aware that not all microbiome test kits are the same. Think about your budget, how the company will analyze your sample, customer reviews, and presentation of results (most companies have a sample report on their website). Also, check if you receive a complete interpretation of your results with the test price or if that is an add-on service.
- Prepare for the test. Follow your regular diet leading up to the test to get the most accurate picture of your typical microbiome (but don’t forget it’s constantly changing!). The test kit may have additional instructions, such as discontinuing probiotics before testing.
- Take your sample. Follow the test kit instructions for sampling and storage carefully to avoid contamination.
- Send your sample. Send your sample as per the test kit instructions. Many companies send a prepaid envelope.
- Await your results. How long it takes to receive your results depends on the company. You should be able to find information about this on their website before purchasing the test.
Remember: Your results cannot diagnose any medical conditions, but they may provide insight into your gut’s overall health.
Can You Improve Your Gut Health Without Doing a Test?
Absolutely! There are many ways to support your microbiome through food choices and lifestyle habits. Here are a few ideas:
- Eat more fermented foods
- Drink enough fluids
- Eat more fiber
- Eat less processed foods
- Move your body regularly
- Prioritize your sleep
- Learn to manage stress
- Spend more time outside
These factors can influence your gut and microbiome health over time, helping you create an environment where beneficial bacteria and other microorganisms can thrive.
The health of your microbiome is essential for your overall health, but gut health testing doesn’t have all the answers (yet!). You may be able to gain some intriguing information, but you must interpret it in context and with a skilled provider. We have a long way to go before microbiome testing is robust enough to be used for individually-targeted medical advice.
Resource Links:
- “A communal catalogue reveals Earth’s multiscale microbial diversity” via Nature
- “Microbiome 101: Studying, Analyzing, and Interpreting Gut Microbiome Data for Clinicians” via Clinical Gastroenterology and Hepatology
- “Gut microbiota and IBD: causation or correlation?” via Nature Reviews: Gastroenterology and Hepatology
- “Current Sampling Methods for Gut Microbiota: A Call for More Precise Devices” via Frontiers in Cellular and Infection Microbiology
- “Towards Novel Non-Invasive Colorectal Cancer Screening Methods: A Comprehensive Review” via Cancers
- “Role of the gut microbiota in nutrition and health” via BMJ
- “Gut microbiome and health: mechanistic insights” via Gut
- “Functional circuits and signal processing in the enteric nervous system” via Cellular and Molecular Life Sciences
- “Revised Estimates for the Number of Human and Bacteria Cells in the Body” via PLoS Biology
- “Effect of water flow and chemical environment on microbiota growth and composition in the human colon” via Proceedings of the National Academy of Sciences of the United States of America
