If you struggle with digestive distress, skin problems, anxiety, or even chronic disease, gut dysbiosis may be the culprit!
In the last few years, the gut microbiome and gut dysbiosis have become popular topics in the media. You probably have heard that our gut health affects the health of our entire body. And it’s true! Having a healthy gut microbiome not only affects digestive health, but also a range of other health conditions. However, it can be hard to disentangle fact from fiction, and know what steps will truly optimize your gut health. If you’ve ever wondered how to eat to prevent or treat gut dysbiosis, keep on reading!
What is Gut Dysbiosis?
Trillions of organisms reside in our gastrointestinal tract, which collectively are known as the gut microbiota. These populations offer us countless benefits such as maintaining the integrity of our mucosal barrier (preventing increased gut permeability or “leaky gut”); protecting against harmful pathogens; modulating our immune system; synthesizing vitamins, enzymes, and amino acids; and aiding in nutrient absorption and metabolism (1). Many of these benefits result from compounds produced by gut microbes called short chain fatty acids (SCFAs). SCFAs provide energy for intestinal cells, have anti-inflammatory properties, and are used by gut bacteria for a range of other purposes as well (1).
While some species, such as Lactobacillus and Bifidobacteria, produce these benefits, others can bring about negative health outcomes. An imbalance of gut microbiota, called “dysbiosis,” is linked to increased gut permeability, inflammation, immune and nervous system dysfunction, an imbalance of neurotransmitters and hormones, insulin resistance, and worsened lipid profiles (1) (2). These in turn increase the risk of many gastrointestinal and metabolic diseases such as cardiovascular disease, type 2 diabetes, obesity, cancer, irritable bowel syndrome (IBS), inflammatory bowel disease (IBD), and fatty liver disease, among others (1). Therefore, keeping a healthy balance of bacteria in our gut is extremely important for our overall well-being!
So, what can you do to avoid or treat dysbiosis? Luckily, there are steps you can take to create a healthy gut microbiome! The numbers and types of microbes in our gut are constantly changing, as they are affected by stress, medications, obesity, physical activity, alcohol, and other factors. But, potentially the factor with the greatest impact is our diet. In fact, microbiome changes can be detected after only 1-2 days of making a dietary change (3). Let’s dive into the specific dietary changes that may help or harm our gut microbiome!
High Fibre Diet
The evidence for a high fibre diet improving gut health is strong. Unfortunately, most Canadians only consume about half the recommended daily intake (4). This low fibre intake leads to a gradual decline in microbial diversity, which is believed to explain the recent increase in chronic digestive diseases (1). To increase your fibre intake, incorporate more fruits, vegetables, legumes, nuts, seeds, and whole grains into your diet!
Gut bacteria ferment these fibres and produce SCFAs. A diet with a greater amount and variety of fibre yields greater SCFA production and subsequent benefits (2). Therefore, it’s a great goal to not only try to eat more fibre overall, but from a wider range of sources! This could be as simple as eating blueberries instead of your usual choice of raspberries, buying a new type of vegetable in the grocery store, or occasionally swapping rice for quinoa.
Foods rich in fibre also tend to be rich in polyphenols. Polyphenols counter dysbiosis through their antibacterial and anti-inflammatory properties, and by increasing Bifidobacteria and Lactobacillus which can alleviate IBS symptoms (1). Once again, variety is key here as similar to fibre, different plant foods contain different types of polyphenols.
High MAC Diet
Microbiota-accessible carbohydrates (MACs) are especially important for the health of our microbiome. MACs are types of carbohydrates that are indigestible to humans but are available for gut microbe metabolism. These include fermentable fibres and non-digestible polysaccharides in resistance starch foods (3). You may have heard the term “prebiotics” before, which are simply a type of MAC associated with increased growth of beneficial bacteria and related health benefits.
High MAC intake promotes a stronger intestinal barrier, as well as increased SCFA production and microbiota diversity including the growth of Lactobacillus. Additionally, consumption of the MAC inulin has been shown to improve stool consistency and well-being in adults suffering from constipation. Animal research shows MACs may also prevent C. difficile infection (a common cause of diarrhea) (2).
MACs are primarily found in cereals and some fruits and vegetables. For example, garlic, onions, artichokes, asparagus, bananas, and chicory root contain the MACs inulin and oligofructose. Despite promoting good gut health, it is important not to overdo MAC intake. Both too little and too much can cause digestive discomfort, particularly in those who suffer from IBS. For example, high inulin intake can worsen flatulence (1).
Supplements
Probiotics
Probiotics may also help treat gut dysbiosis. Probiotics are live microorganisms that when consumed in sufficient amounts lead to health benefits. Certain strains (primarily Bifidobacterium and Lactobacillus species) produce antimicrobial compounds which prevent the growth of competing pathogens (1). However, more research is needed on which strains confer which health benefits. It is also important to remember that taking probiotics does not replace the need for a balanced diet!
Synbiotics
Synbiotics refers to combining probiotics and prebiotics that work synergistically to promote health. One example would be a yogurt that contains both inulin and B lactis bacteria. Much like fibre and probiotics, some synbiotics can restore microbiota equilibrium and alleviate IBS symptoms. The main challenge remains the limited number of studies on the effects of different types of synbiotics (1).
Fibre Supplement: Psyllium
While it is important to prioritize food sources of fibre first, fibre supplements can also produce similar outcomes. Specifically, psyllium is a prebiotic soluble fibre that when fermented by microbiota produces SCFAs, thus fostering a balanced microbiome (1).
Dietary Patterns that Support Gut Health
The Mediterranean Diet
The Mediterranean diet is renowned for its chronic disease-fighting properties. This association is in part attributable to its favourable impact on the gut microbiome. Specifically, it may fight dysbiosis by increasing SCFAs and microbiome diversity and decreasing the pathogen E Coli. A Mediterranean diet has been shown to lower the Firmicutes/Bacteroidetes (F/B) ratio, meaning lower levels of Firmicutes and higher levels of Bacteroidetes bacteria (2). This profile is associated with better gut and metabolic health, indicated by lowered inflammation, obesity, and lipid levels (3). Omega 3 fatty acids in particular can restore the F/B ratio and increase SCFA production (2).
To adhere to the principles of the Mediterranean diet, aim to incorporate more olive oil, nuts, whole grains, fruit, vegetables, legumes, poultry, and fish in your diet while limiting processed meats, sweets, and other processed foods. This eating pattern is high in polyunsaturated fatty acids (such as omega 3s), monounsaturated fatty acids (like in nuts and olive oil), fibre, complex carbohydrates, polyphenols, antioxidants, and micronutrients.
Vegetarian/Vegan Diets
Vegetarian diets are associated with similar benefits to the Mediterranean diet including more SCFAs and Lactobacillus bacteria and less pathogenic bacteria (3). This may partly be because people following a vegetarian diet are more likely to eat pulses which can increase beneficial bacteria and reduce gut inflammation (2).
However, some studies find no significant difference in SCFA levels between omnivores and vegetarians/vegans. This may be because the benefits arise not because of the elimination of meat, but rather from increasing fibre intake and variety. This is likely why the Mediterranean diet (which does not eliminate meat) produces similar benefits; both diets are high in fibre and MACs (3). Therefore, whether you wish to eat vegetarian or not, it is important to focus on eating a wide variety of plant based foods such as legumes to avoid dysbiosis.
Dietary Patterns that May Worsen Dysbiosis
The Low FODMAP Diet (1)
While the low FODMAP diet is well supported for managing IBS symptoms, it can be detrimental to the microbiome if followed long term. This is because the diet restricts various types of carbohydrates that are fermented by gut bacteria. Although this fermentation is responsible for GI symptoms in sensitive individuals, it also leads to SCFA production and a healthy, diverse gut microbiome. Some FODMAPs such as oligosaccharides, fructans, and GOS are prebiotic fibres, thus conferring the benefits discussed above. Meanwhile, the polyols (the “P” of “FODMAPs”) erythritol and lactitol increase Bifidobacteria and good gut health. A mere 2-4 weeks on a low FODMAP diet can significantly decrease Bifidobacteria. Therefore, while a low FODMAP diet is a useful tool for identifying individual food sensitivities, it should only be followed short term and with the guidance of a Registered Dietitian (RD).
Gluten Free Diets
Another diet commonly used for IBS management is the gluten free diet, as many people with IBS report symptom relief upon eliminating gluten. However, a gluten free diet can reduce beneficial bacteria like Bifidobacterium adolescentis and Faecalibacterium prausnitzii (1).
Generally, restricting any food group decreases the diversity of fibre types and thus diversity of gut microbes. It is crucial to follow a gluten free diet if you have diagnosed celiac disease, but otherwise it may worsen rather than alleviate gut dysbiosis. Of note, some people without diagnosed celiac are sensitive to gluten-containing foods not due to the gluten itself, but rather to the FODMAP fructans found in wheat. It may be worthwhile working with an RD to investigate if you are sensitive to other fructan-containing foods such as onions, garlic, cabbage, kidney beans, raisins, and dark chocolate, and to determine the amount/threshold of these foods you can tolerate.
Western Diet
The standard diet in many western countries such as Canada and the US is high in saturated fat, processed meat, processed foods, food additives, and refined carbohydrates while being extremely devoid of fibre and MACs.
This way of eating decreases microbial diversity and hinders the functionality of the microbiota (3). It is associated with a higher F/B ratio, gut permeability, insulin resistance, and systemic inflammation (2). For example, a high fat diet can cause inflammatory responses by increasing the endotoxin lipopolysaccharide (LPS) levels (3).
The Bottom Line
There are many dietary factors that can improve or worsen gut microbiota equilibrium. Each individual’s microbiome and response to these dietary factors will vary, making a personalized approach key. Nonetheless, there are some common principles that can tackle dysbiosis for most people, such as:
- Focus on whole foods like fruits, vegetables, meat, dairy, eggs, grains, legumes, nuts, and seeds
- When selecting processed foods:
- Select nutrient-rich foods with fewer ingredients such as yogurt, rolled oats, protein powders without artificial sweeteners, and fortified whole grain cereals, breads, and pastas
- Limit ultra-processed foods like chips, candy, processed meat, and pop
- Prepare food at home more often and reduce how often you eat out or get takeaway
- Don’t cut out food groups unnecessarily
- Above all, incorporate more fibre from a wide variety of sources
- Mix up the types of fruits and vegetables you cook with
- Buy mixes such as mixed nuts, mixed grains, or mixed berries
- Use at least 3 different vegetables and 1 whole grain each lunch and dinner when possible
- For further support, work 1-on-1 with an RD to discover the eating pattern that works best for you!
The way we eat can have a huge impact on the health of our gut. Since dysbiosis is a common feature of many diseases and conditions, the dietary choices you make every day can be the key to your long term health! If you suspect you may have dysbiosis, or are struggling with other health or digestive symptoms, contact us to get started working with a gut-specialized Registered Dietitian – we can help!
References
1. Thomas A, Thomas A, Butler-Sanchez M. Dietary modification for the restoration of gut microbiome and management of symptoms in irritable bowel syndrome. Am J Lifestyle Med. 2021. 2021 May 10;16(5):608–21. https://www.doi.org/10.1177/15598276211012968.
2. Rinninella E, Tohumcu E, Raoul P, Fiorani M, Cintoni M, Mele MC, et al. The role of diet in shaping human gut microbiota. Best Pract Res Clin Endocrinol Metab. 2023 Feb;62–63:101828. https://www.doi.org/10.1016/j.bpg.2023.101828.
3. Martinez JE, Kahana DD, Ghuman S, Wilson HP, Wilson J, Kim SC, et al. Unhealthy lifestyle and gut dysbiosis: A better understanding of the effects of poor diet and nicotine on the intestinal microbiome. Front Endocrinol. 2021 Jun 8;12. https://www.doi.org/10.3389/fendo.2021.667066.
4. Canada.ca [Internet]. Government of Canada; 2019 [updated 2019 Jan 22; cited 2025 Jun 4]. Fibre; [about 2 screens]. Available from: https://www.canada.ca/en/health-canada/services/nutrients/fibre.html.
Leave a Reply