In the last decade or so, tens of thousands of gut microbiome research articles have been published. From digestion and metabolism to immune defense and even brain activity, gut microbes play important (if somewhat understated) roles in regulating your health and well-being.
Gut microbiome science is full of opportunity, and there’s heaps of hope that it may provide for new ways to predict or diagnose diseases, or even augment your strength or athletic performance. In the health and fitness space, gut microbiome science has exploded into something resembling both a new field of science and a compelling dietary fad; “gut health.”
And, as with any emerging scientific field, it’s vulnerable to pseudoscience, exaggeration, and potentially dishonest marketing. You need a strong stomach to sift through the science. Luckily, we’ve separated the wheat from the chaff on gut health so you can make an informed decision. Here’s what the science has to say, and why it matters.
- What Is Gut Health?
- What the Science Says
- How to Improve Your Gut Health
- Best Supplements for Gut Health
Editor’s Note: The content on BarBend is meant to be informative in nature, but it should not be taken as medical advice. When starting a new training regimen and/or diet, it is always a good idea to consult with a trusted medical professional. We are not a medical resource. The opinions and articles on this site are not intended for use as diagnosis, prevention, and/or treatment of health problems. They are not substitutes for consulting a qualified medical professional.
What Is Gut Health?
The term “gut health” is used so often, you might assume that there’s a formal definition somewhere, but that’s not the case. Related terms — like dysbiosis and diversity — are used in gut microbiome research, but gut health is a colloquial term that can mean anything (or nothing).
In most cases, people are probably referring to one or all of the following factors when they say “gut health”:
- How well they digest and absorb nutrients and eliminate waste, and how they feel after eating.
- How well they manage their gastrointestinal (GI) disease, if one is present, or prevent certain GI diseases.
- The diversity of their gut microbiome.
These factors are related, but research is just beginning to uncover what might link the gut microbiome to digestion and disease progression.
What the Science Says
It’s logical to assume that a healthy gut only contains “good” microbes, but this isn’t the case at all. Some microbes are only known to perform beneficial functions, like the production of certain short-chain fatty acids that our intestinal cells use for energy. Others don’t seem to do anything in your favor, but they don’t appear to cause disease, either.
Some — known as opportunistic pathogens — can cause disease if their relative abundance becomes high enough, either through their own proliferation or the loss of other species. (1)
Your microbiome is as unique as your fingerprint, and there isn’t yet enough high-quality data to establish widely-applicable reference ranges of the total number or proportions of gut microbes that should be present. Many reference ranges used by consumer gut microbiome testing companies are set by the manufacturers based on a selected cohort of healthy people. (1)(2)
In fact, science hasn’t yet identified all of the bacterial species to be found in every human microbiome, and bacteria are only one portion of the community (though they do make up a majority). Even less has been concretely established about the fungi, archaea, parasites, and viruses inhabiting the human digestive tract. (1)
This means that you could have an asymptomatic condition or digestive discomfort without a disease, and in either case, there is no way of establishing a cause-and-effect relationship with your specific set of microbes. In other words — and contrary to popular belief — your gut microbiome isn’t an established root cause of disease (or health, for that matter). (2)
Without a consensus on what constitutes a healthy gut microbiome (or eubiosis), there’s no way to create a universal definition of dysbiosis. Despite its negative connotation, it doesn’t mean a microbiome is unhealthy. It’s simply different from the comparison sample. (3)
Leaky Gut Isn’t a Root Cause, Either
One main theory linking the gut microbiome to health and disease implicates so-called leaky gut; one that’s excessively permeable. Leaky gut is a supposed indicator of health issues ranging from brain fog to autoimmune disease.
Although intestinal permeability is a measurable phenomenon, it doesn’t always occur in the presence of other symptoms. Leaky gut hasn’t been conclusively established as a cause of any disease. It seems more common in those who suffer from certain illnesses, but it’s not yet possible to determine whether it’s a cause or consequence of the disease. (4)
How to Improve Your Gut Health
Even though “gut health” isn’t easily defined or measured, there are some things you can do to improve your bowel habits, protect against colorectal cancer, support a resilient microbiome, and manage some disease symptoms.
Eat A Plant-Heavy Diet
When it comes to modifying the gut microbiome and supporting your health from the inside out, your dietary pattern is one of the most influential factors. Plant-free, all-meat diets might be popular at the moment, but they can’t compare with the evidence supporting plant-inclusive dietary patterns.
Your gut health may benefit from including more fruits and vegetables on a daily basis. The added micronutrients certainly won’t hurt either, both from a health and performance perspective.
Include Dietary Fiber
Dietary patterns that include plenty of whole grains, fruits, vegetables, and beans can reduce the odds of becoming constipated, whereas inadequate fiber intake can lead to bowel-related irregularity. (5)(6)
Fiber creates bulk and holds water in the stool to make it easier to pass. Gut microbes can also convert it to short-chain fatty acids that regulate intestinal smooth muscle contractions. These factors can all increase the regularity of bowel movements. (5)(6)
Plant-heavy diets may lead to feeling bloated for some. If that’s the case for you, there are certainly some actions you can take.
Eat the Right Carbs
A huge body of literature shows that diet is one of the most influential and modifiable risk factors for developing colon cancer later in life. Compared to a Westernized diet, following a more prudent dietary pattern — like the Mediterranean or Dietary Approaches to Stop Hypertension (DASH diet) — may reduce your risk of colon cancer by about 20 percent, according to some research. (7)(8)
If you don’t want to follow a specific or branded diet, you need only look at what they have in common. They both include plenty of minimally or unprocessed whole grains, fruits, and vegetables, with limited amounts of sodium, saturated fat, added sugars, and red meat. (7)(8)
Whole grains appear to be the most consistently protective against colorectal cancer, but there’s also evidence supporting fruit and vegetable intake, as they all contribute dietary fiber and beneficial plant compounds called polyphenols. (9)
Both fiber and polyphenols have positive effects on the microbiome, supporting the growth of beneficial microbes and the production of postbiotics (health-promoting compounds created during microbial metabolism.) (7)(8)(9)
Make Diverse Food Choices
Microbiome diversity refers to the richness (or number of different types of microbes) and evenness (their relative proportions) of the population living in your gut. Generally speaking, more gastrointestinal diversity is regarded as a good thing, because it often means a high level of functionality (from lots of genetic material) and resiliency. (2)
In other words: If some microbes are killed off due to an environmental stressor — like antibiotics, for example — there will still be many microbes available to pick up the slack and maintain the overall functionality of the microbiome. (1)(2) (the “right” level of diversity hasn’t been determined yet, so it’s hard to conclusively know just how diverse your microbiome is). (3)
Like organisms in any ecosystem, these microbes interact with each other. They may share, compete for, or even provide resources to other microbes. To make energy, most gut microbes rely on the indigestible carbohydrates — fiber and resistant starch — that you eat. These are sometimes referred to as microbe-accessible carbohydrates, or MACs.
Dietary diversity seems to correlate with gut microbiome diversity, so the most prudent recommendation is to eat a wide variety of MACs from whole grains, fruits, vegetables, legumes, and nuts. (1)(2)
While you don’t need to follow a vegan or vegetarian diet, it’s just as important to hit your daily fiber goal as it is to hit your protein target.
Add (Some) Fermented Dairy
Although fermented foods may contain live microbes, only fermented dairy is considered a probiotic food because it meets the specific definition of a probiotic (unlike other ferments, such as kimchi.) Fermented dairy with live cultures — like kefir or certain yogurts — can reduce antibiotic-associated diarrhea and may also protect against colorectal cancer. (10)(11)
Best Supplements for Gut Health
Not everyone needs a gut health supplement, but there are a few options that could be useful for people with irritable bowel syndrome (IBS), inflammatory bowel disease (IBD), or diarrhea.
Peppermint Oil & Glutamine
Peppermint oil can ease IBS-associated abdominal pain, and some emerging evidence suggests that glutamine might also improve IBS symptoms and reduce markers of intestinal permeability in people with post-infectious IBS. (12)(13)
Probiotics
Probiotics can also improve IBS and IBD symptoms, reduce antibiotic-associated diarrhea, and prevent traveler’s diarrhea (the type picked up by ingesting contaminated food or water). However, the effects of probiotics are strain-specific, so you could be flushing your money away if you’re using a random blend and missing the microbes you really need. (14)(15)
Supplements You Can Skip
Despite their popularity, greens powders, collagen, and bone broth aren’t supported by meaningful scientific evidence yet. While a fiber supplement might help you have a bowel movement, you don’t necessarily need to supplement if you’re getting enough fiber in your diet.
Certain digestive enzymes could reduce feelings of gas and bloating, but improvements aren’t consistent between different studies, so your results may vary. (16)
Your supplement choices for muscle growth or recovery should be couched in firm, well-scrutinized scientific evidence; products you pick up to help with gut health should be scrutinized just as closely.
Work On Your Overall Health
The basics of health promotion for the human body — like exercising, limiting alcohol intake, and managing stress — are just as effective for promoting gut health as they are for helping you add some muscle, lose fat, or get a bit stronger.
Good cardiovascular health and regular exercise are linked to microbiome diversity and high levels of beneficial microbes. (17) Drinking more than one alcoholic beverage per day, on the other hand, likely increases the risk of colon cancer. (18) There’s also some evidence that significant stress is associated with more severe gastrointestinal disease symptoms. (19)
If you’re already exercising regularly, limiting alcohol, and managing stress, you have a solid foundation. If not, turning toward your top-level health habits is a productive place to begin. Grabbing a gut health supplement off the bat may be ignoring the root cause of your distress.
Gut Health & Physical Activity
Good cardiovascular health and regular exercise are linked to microbiome diversity and high levels of beneficial microbes. (20) Some studies have examined the effects of dietary patterns on the microbiomes of bodybuilders: In addition to finding lower microbial diversity at higher fat intakes, they also found that the microbiomes of fiber-deficient bodybuilders were more similar to sedentary controls than to the bodybuilders taking in adequate fiber. (21)(22)
It’s possible that the microbiome could influence endurance performance and muscle mass. Recent studies have shown that endurance athletes harbor microbes that convert lactate to propionate, a short-chain fatty acid that improves exercise performance in mice.(23)
In the past few years, the gut-muscle axis has also been explored as a potential explanation for age-related muscle loss, but a causal relationship hasn’t been established. (24) It’s likely, though, that dietary patterns, physical activity, and the microbiome interact in a synergistic way that has yet to be fully explained.
Trust Your Gut
Gut health is more than just a current trend; it really is important to keep your microbes in mind when looking for ways to support your health. By eating a varied diet, staying active, limiting alcohol, managing stress, abstaining from smoking, and using supplements judiciously, you can support your health from the inside out.
References
1. Rinninella, E., Raoul, P., Cintoni, M., Franceschi, F., Miggiano, G., Gasbarrini, A., & Mele, M. C. (2019). What is the Healthy Gut Microbiota Composition? A Changing Ecosystem across Age, Environment, Diet, and Diseases. Microorganisms, 7(1), 14.
2. Cani, P. D., Moens de Hase, E., & van Hul, M. (2021). Gut Microbiota and Host Metabolism: From Proof of Concept to Therapeutic Intervention. Microorganisms, 9(6), 1302.
3. Brüssow, H. (2020). Problems with the concept of gut microbiota dysbiosis. Microbial Biotechnology, 13(2), 423–434.
4. Vanuytsel, T., Tack, J., & Farre, R. (2021). The Role of Intestinal Permeability in Gastrointestinal Disorders and Current Methods of Evaluation. Frontiers in nutrition, 8, 717925.
5. Buddington, R. K., Kapadia, C., Neumer, F., & Theis, S. (2017). Oligofructose Provides Laxation for Irregularity Associated with Low Fiber Intake. Nutrients, 9(12), 1372.
6. de Vries, J., Le Bourgot, C., Calame, W., & Respondek, F. (2019). Effects of β-Fructans Fiber on Bowel Function: A Systematic Review and Meta-Analysis. Nutrients, 11(1), 91.
7. Illescas, O., Rodríguez-Sosa, M., & Gariboldi, M. (2021). Mediterranean Diet to Prevent the Development of Colon Diseases: A Meta-Analysis of Gut Microbiota Studies. Nutrients, 13(7), 2234.
8. Tangestani, H., Salari-Moghaddam, A., Ghalandari, H., & Emamat, H. (2020). Adherence to the Dietary Approaches to Stop Hypertension (DASH) dietary pattern reduces the risk of colorectal cancer: A systematic review and meta-analysis. Clinical Nutrition, 39(10), 2975–2981.
9. Zhang, X. F., Wang, X. K., Tang, Y. J., Guan, X. X., Guo, Y., Fan, J. M., & Cui, L. L. (2020). Association of whole grains intake and the risk of digestive tract cancer: A systematic review and meta-analysis. In Nutrition Journal (Vol. 19, Issue 1). BioMed Central Ltd.
10. Zhang, K., Dai, H., Liang, W., Zhang, L., & Deng, Z. (2019). Fermented dairy foods intake and risk of cancer. International Journal of Cancer, 144(9), 2099–2108.
11. Dimidi, E., Cox, S. R., Rossi, M., & Whelan, K. (2019). Fermented Foods: Definitions and Characteristics, Impact on the Gut Microbiota and Effects on Gastrointestinal Health and Disease. Nutrients, 11(8), 1806.
12. Alammar, N., Wang, L., Saberi, B., Nanavati, J., Holtmann, G., Shinohara, R. T., & Mullin, G. E. (2019). The impact of peppermint oil on the irritable bowel syndrome: a meta-analysis of the pooled clinical data. BMC Complementary and Alternative Medicine, 19(1), 21.
13. Zhou, Q., Verne, M. L., Fields, J. Z., Lefante, J. J., Basra, S., Salameh, H., & Verne, G. N. (2019). Randomised placebo-controlled trial of dietary glutamine supplements for postinfectious irritable bowel syndrome. Gut, 68(6), 996–1002.
14. McFarland, L. v., Karakan, T., & Karatas, A. (2021). Strain-specific and outcome-specific efficacy of probiotics for the treatment of irritable bowel syndrome: A systematic review and meta-analysis. EClinicalMedicine, 41, 101154.
15. Agamennone, V., Krul, C., Rijkers, G., & Kort, R. (2018). A practical guide for probiotics applied to the case of antibiotic-associated diarrhea in The Netherlands. BMC gastroenterology, 18(1), 103.
16. Edakkanambeth Varayil, J., Bauer, B. A., & Hurt, R. T. (2014). Over-the-counter enzyme supplements: what a clinician needs to know. Mayo Clinic Proceedings, 89(9), 1307–1312.
17. Tarracchini, C., Fontana, F., Lugli, G. A., Mancabelli, L., Alessandri, G., Turroni, F., Ventura, M., & Milani, C. (2022). Investigation of the Ecological Link between Recurrent Microbial Human Gut Communities and Physical Activity. Microbiology spectrum, 10(2), e0042022.
18. Zhong, L., Chen, W., Wang, T., Zeng, Q., Lai, L., Lai, J., Lin, J., & Tang, S. (2022). Alcohol and Health Outcomes: An Umbrella Review of Meta-Analyses Base on Prospective Cohort Studies. Frontiers in Public Health, 10.
19. Schoultz, M., Beattie, M., Gorely, T., & Leung, J. (2020). Assessment of causal link between psychological factors and symptom exacerbation in inflammatory bowel disease: a systematic review utilising Bradford Hill criteria and meta-analysis of prospective cohort studies. Systematic Reviews, 9(1), 169.
20. Tarracchini, C., Fontana, F., Lugli, G. A., Mancabelli, L., Alessandri, G., Turroni, F., Ventura, M., & Milani, C. (2022). Investigation of the Ecological Link between Recurrent Microbial Human Gut Communities and Physical Activity. Microbiology spectrum, 10(2), e0042022.
21. Jang, L. G., Choi, G., Kim, S. W., Kim, B. Y., Lee, S., & Park, H. (2019). The combination of sport and sport-specific diet is associated with characteristics of gut microbiota: an observational study. Journal of the International Society of Sports Nutrition, 16(1), 21.
22. Son, J., Jang, L. G., Kim, B. Y., Lee, S., & Park, H. (2020). The Effect of Athletes’ Probiotic Intake May Depend on Protein and Dietary Fiber Intake. Nutrients, 12(10), 2947.
23. Scheiman, J., Luber, J. M., Chavkin, T. A., MacDonald, T., Tung, A., Pham, L. D., Wibowo, M. C., Wurth, R. C., Punthambaker, S., Tierney, B. T., Yang, Z., Hattab, M. W., Avila-Pacheco, J., Clish, C. B., Lessard, S., Church, G. M., & Kostic, A. D. (2019). Meta-omics analysis of elite athletes identifies a performance-enhancing microbe that functions via lactate metabolism. Nature Medicine 2019 25:7, 25(7), 1104–1109.
24. Liu, C., Cheung, W. H., Li, J., Chow, S. K., Yu, J., Wong, S. H., Ip, M., Sung, J., & Wong, R. (2021). Understanding the gut microbiota and sarcopenia: a systematic review. Journal of cachexia, sarcopenia and muscle, 12(6), 1393–1407.
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