The impact of a good diet on our health is well-known and continuously researched. Most of us know to cut back on red and processed meats, reduce our sugar intake, and eat a variety of vegetables, fruit, and whole grains. These things provide us with the vitamins, minerals, and protein necessary for our body to function well. But what happens once these foods reach our intestinal tract?
Digestion is more than our body breaking food down into nutrients and waste; it is a delicate system involving trillions of good and bad bacteria. When the balance of beneficial and harmful bacteria is disrupted, it puts us at risk for common gastrointestinal ailments, such as diarrhea and indigestion, or more severe diseases, such as cardiovascular disease and diabetes.¹ Probiotics and prebiotics can help regain this balance and promote better health.
When we eat, we’re feeding ourselves and the 100 trillion bacteria that live on and in our bodies. Over 1,000 species of microorganisms called microbiota live and thrive in our intestinal tract, creating the gut microbiome.¹ Our relationship with these microorganisms is symbiotic; the gut provides the environment and food, and, in return, the bacteria contribute to functions vital to our health and well-being.
The beneficial bacteria in the gut microbiome are responsible for producing or synthesizing a large portion of vitamins, including most B vitamins (such as folate, biotin, thiamine, pantothenic acid, and riboflavin) and nearly half of our daily vitamin K requirement.² Gut microbiomes also produce short-chain fatty acids (SCFAs) — such as acetate, propionate, and butyrate — by digesting fiber. SCFAs impact many areas of the body, including water absorption, CO2 production, blood flow, and even skeletal and muscle function.²
Some other important tasks the gut microbiome performs include:¹
Probiotics and prebiotics act like relief workers for a struggling gut microbiome. A shift in the balance of bacteria is called dysbiosis; there may be a decrease in diversity or loss of beneficial bacteria or an increase in disease-causing bacteria. The imbalance could also be due to certain health conditions.³ Whatever the case, probiotics and prebiotics work together to bring balance back to the gut microbiome.
Although you can find probiotics and prebiotics in many different foods, it’s more effective to take them as supplements. Probiotics and prebiotic supplements are often tailored to many different conditions like weight loss, increased energy, and digestive health, but their main goal is always to support the gut microbiome.
Probiotics are products or food which contain a high number of living microbes or bacteria, adding to the microbiota already in the gut microbiome. Probiotics replenish and boost the number of microbes as a means to prevent or heal dysbiosis.⁴ Although probiotics are very popular, there is still some confusion surrounding the differences between bacteria genera, species, and strains.
If you’ve looked closely at a bottle of kefir, you may have seen Lactobacillus in the ingredients and assumed it was a probiotic strain. Lactobacillus is a genus (type) of bacteria with many different species, and each species has many different strains.
This scientific classification is the same one you’ll find for larger organisms. For example, the genus Panthera contains multiple species, such as lions, tigers, and jaguars. Within these species, there are different breeds, such as the Bengal tiger, the African leopard, and the Barbary lion.⁵ The same principle applies to bacterial taxonomy.
Here’s a quick run-down on the four genera of beneficial bacteria you might find in a probiotic.
These lactic acid-producing bacteria (LAB) are found in yogurt and cheese and used in fermentation for wine, pickles, and cider. The most popular species of lactobacillus include L. reuteri, L. rhamnosus, L. acidophilus, and L.casei. Strains beneficial to human health include L. reuteri DSM 17938, L. reuteri RC-14, L. rhamnosus GG, and L. casei Shirota. These strains show benefits for digestive issues, vaginal problems, ADHD, and upper respiratory infections.⁶
This is the most common type of bacteria found in the digestive tracts of healthy breastfed babies. Research has shown that lower quantities of Bifidobacterium are present in formula-fed infants, which may account for their higher rates of diarrhea and allergies. The number of Bifidobacterium in the digestive system decreases with age. Species of Bifidobacterium include B. infantis, B. lactis, and B. breve. Strains used to improve health include B. infantis 35624, B. lactis Bi-07, and B. breve M-16V. These have been effective in some studies for immune support and treating inflammation, IBS symptoms, and depression.⁶
Saccharomyces is a yeast (fungal) genus with several different species used in bread and alcohol fermentation. The most popular species of saccharomyces is S. cerevisiae. S.cerevisiae boulardii is among the most researched strains and is the only yeast labeled as a probiotic. It removes pathogenic microbes and has antifungal properties.⁶
Bacillus is among the most diverse genera of bacteria and has medical, holistic, and agricultural applications. The species B. coagulans is popular for its ability to withstand high temperatures, acidity, and pressure. This resilience allows the manufacturers to make the probiotic as a chewable tablet or gummy instead of a capsule. Strains beneficial to human health include B. coagulans Unique-IS2 and B. coagulans BC30, which promote gastrointestinal health and protein absorption.⁶
While you can find these probiotics in food, supplements have them in higher quantities. Probiotic strains in food, such as certain yogurts, kimchi, and cheeses, may not reach the digestive system alive due to high temperatures, acidity, and pressure in the body. This is also why some probiotic supplements are delivered in capsule form while more resilient probiotic strains are delivered in chewable or gummy form.⁶ Supplements usually contain a mix of different species and strains rather than offering a single strain. However, they don’t always provide important information about the strains they use in their products.
Often you’ll only see an amount listed as a colony-forming unit (CFU). For example, you may see 1 x 10^10 CFU, meaning the product has 10 billion microbes. Currently, manufacturers are only required to disclose the total microbe amount, whether alive or dead. Because of this, it’s difficult to determine how beneficial the product will be.⁷ Choosing products with at least one billion CFUs of resilient strains, such as the ones mentioned above, is the best way to ensure you’re getting your money’s worth.
Prebiotics are the food source of probiotics and are the key to a healthy and thriving gut microbiome. You can get prebiotics from fibers and resistant starches that come from a long list of different fruits, vegetables, and whole grains including:⁸
Because humans can’t digest the fibers from these foods, we rely on the microbiome to metabolize them. A diet inclusive of resistant carbohydrates and fiber keeps the microbiota well-fed and producing vitamins and SCFAs while starving out pathogenic bacteria. These foods also appear to promote immunity, reduce cholesterol, and improve insulin resistance by improving the quality of your gut microbiome.⁹
Evidence suggests that eating too many prebiotic foods can negatively impact IBS patients, requiring more research to determine the best prebiotic and dosage for people with this condition.⁸ Like probiotic supplements, prebiotics are sold as powders, gummies, capsules, and tablets.
Without probiotics and prebiotics, the gut microbiome suffers, as does our health. Disruptions in the balance of beneficial to pathogenic microbes contribute to many health problems. Dysbiosis can involve increased pathogenic bacteria, decreased diversity, or loss of beneficial bacteria.³ These disruptions are correlated with many things, such as:³
Essentially, the fewer nutrients you send to your gut microbiome or the more disruptive agents (such as alcohol or antibiotics), the more likely you are to experience dysbiosis.
Dysbiosis symptoms vary from person to person but can include typical ailments such as diarrhea, constipation, gas, bloating, and vomiting. More uncommon symptoms might look like increased sugar cravings, carbohydrate cravings, and skin problems.¹⁰ Diseases and conditions linked to dysbiosis include:¹¹
The research on the effect of dysbiosis is ongoing, and it’s often unclear whether dysbiosis causes or is caused by disease.³ For example, eating a diet high in sugar and low in fiber can cause a decrease in SCFAs, which are produced when the microbiota breaks down plant fibers. This decrease in SCFAs can result in inflammation, which is associated with other health problems like heart disease and weight gain.¹¹ Dysbiosis is also a common symptom in many other diseases in which pathogenic strains have overwhelmed beneficial microbes or a severe lack of beneficial bacteria. People with alcoholic liver disease tend to have an excessive amount of Candida albicans, a fungal microbe, and those with IBD have a marked decrease in microbe diversity.³
Understanding and monitoring the gut microbiome can provide indispensable information about a person’s health, which medical professionals can then use to determine a proper course of treatment. These treatments can include prescribing probiotics and prebiotics to replenish the microbiome, or even microbial restoration, which is transferring healthy bacteria from one patient to another, as in the case of C. Difficile patients.¹
A diet rich in vegetables and commitment to regular exercise is the best way to keep the gut microbiome thriving.¹² For many people, this is an ideal that is difficult to achieve. Time, money, and energy play a huge role in making these healthy choices, and it can be much easier to resort to high-fat and low-fiber foods like macaroni and cheese rather than buying and cooking with fresh vegetables. This type of diet can lead to weight gain, high cholesterol, and heart disease, which are linked to dysbiosis. Dysbiosis can wreak havoc on the body and lower immune responses, triggering inflammation and allowing pathogenic bacteria to thrive.
Prebiotics and probiotics bring balance back to the gut microbiome and promote better immune responses. Eating a diet rich in probiotics and prebiotics keeps the gut microbiome healthy, but probiotic and prebiotics supplements are also available if there is a need for extra support. If you’re curious about your gut microbiome's health, check out our guide to the best microbiome tests.