Our intestines (or what we commonly refer to as the gut) are inhabited by a vast population of bacteria, numbering about 100 trillion and collectively known as the gut microbiota. Most of these bacteria are beneficial to our health, with roles in digestion, production of nutrients, immunity and management of diseases. They also have an important role in metabolism and energy balance, making them one of many determinants of weight. In general, evidence suggests that a balanced and diverse microbiota (with a lot of good bacteria, and not a lot of harmful bacteria) might contribute to better health overall, and a less diverse or less balanced microbiota can have a negative impact on health. Research has shown that having a strong population of good bacteria helps us prevent harmful bacteria from taking over and contributing to conditions like irritable bowel syndrome (IBS) and other digestive distress, diabetes, allergies, liver disease and cardiovascular diseases (1).
The composition of our gut microbiota is dependent on genetics, geographic location, age, medication/drug use, stress, medical conditions, exercise and diet. In fact, microbiota composition is similar in family members, individuals in the same geographic location and individuals of the same age. Our diet & gut bacteria In terms of diet, gut bacteria changes in response to daily meals (short term) and habitual dietary patterns (long term). By altering the numbers and kinds of bacteria present in the gut, diet may help manage diseases (2). For example, diets high in prebiotics promote very favorable changes in gut bacteria and may reduce risks of infections in the gut, inflammation, and chronic disorders; increase the bioavailability of nutrients; and regulate appetite and satiety (3). Prebiotics are types of fibers that provide a major source of energy for pre-existing good bacteria, stimulating their growth and activity. They are found in several fruits, vegetables and whole grains.
Some foods contain probiotics, living strains of bacteria that add to the population of good bacteria in your digestive system. For example, yogurt has been used for thousands of years for its health-promoting properties. Many other fermented foods provide probiotics as well. The potential health benefits of foods that contain probiotics include alleviating diarrhea and constipation; enhancing immune function; protecting against colon cancer and reducing the risk of heart disease and diabetes (4,5).
Bacteria in the gut also produce several vitamins, including biotin, folate, pantothenic acid, riboflavin, thiamin, vitamin B6, vitamin B12, and vitamin K. However, these vitamins are still considered essential nutrients and must be obtained through diet because the levels produced are insufficient to suit the body's demands (2). How we can improve gut health In terms of diet, the best advice I can give you is to try to have a diversified diet filled with whole grains, fruits, veggies and a wide variety of proteins. The more diverse the diet, the more diverse the microbiota. If your diet isn’t too varied at the moment, changing up your diet can actually alter your gut bacteria profile after only a few days (6).
In terms of specifics, we can consume prebiotics and probiotics to have better gut health. Here’s a short list of foods with prebiotics:
- Bananas - Apples - Watermelon - Grapefruit - Jerusalem artichokes - Asparagus - Garlic - Leeks - Onions - Cabbage - Radishes - Barley - Wheat bran - Oats - Lentils, chickpeas and beans - Nuts and seeds (almonds, cashews, pistachios, flaxseeds, etc.) - Cocoa
To add some of these to your diet in a general way, you can try snacking on fruits, nuts and seeds, incorporating more vegetables into your meals, making legume-based meals or adding legumes to salads and soups, and trying oatmeal for breakfast or adding oats to a smoothie.
And, a list of probiotic sources:
- Kefir
- Yogurt (make sure it has “live" or "active" cultures,” or “probiotics” on the label)
- Some cheeses, like cottage cheese, gouda and cheddar (make sure it has “live" or "active" cultures or “probiotics” on the label)
- Kimchi
- Kombucha
- Miso
- Pickles
- Sauerkraut
- Tempeh
- Natto
I personally eat yogurt almost every day and love to have kombucha when I can. However, if these foods aren’t to your liking, there’s always supplements. If you’re interested in taking probiotics for the sake of IBS, constipation or diarrhea relief, there are specific strains that work best for each one of the conditions. For example, Bifidobacterium bifidum and Bifidobacterium infantis seem to work best against IBS. You can use labdoor.com to look for top-rated supplements!
In summary
The gut microbiota is incredibly complex and incredibly important to our health. Having diverse bacteria can help prevent chronic diseases, help with our immunity, help with nutrient absorption, and much more. Therefore, if you have the time, the means and the interest for improving your gut health, go for it! Adding foods with prebiotics and probiotics also have tons of different health-benefitting properties as they carry many other nutrients, such as protein, iron, calcium, potassium, vitamin C… and the list goes on and on.
Works cited
1. Khanna, S. & Pritish, T. A clinician's primer on the role of the microbiome in human health and disease. Mayo Clinic proceedings vol. 89,1 (2014): 107-14.
2. Rolfes, W. et al. Understanding Nutrition, 16th ed., Cengage Learning, 2021.
3. Santos, JG et al. Dietary interventions, intestinal microenvironment, and obesity: A systematic review, Nutrition Reviews 77 (2019): 601–613; J.
4. Kok, CR. & Hutkins, R. Yogurt and other fermented foods as sources of health-promoting bacteria, Nutrition Reviews 76 (2018): 4–15.
5. Fernandez, MA. et al. Yogurt and cardiometabolic diseases: A critical review of potential mechanisms, Advances in Nutrition 8 (2017): 812–829.
6. Heiman, M. & Greenway, F. A healthy gastrointestinal microbiome is dependent on dietary diversity. Molecular metabolism vol. 5,5 317-320. 5 Mar. 2016.