Bacteria for Your Gut? Learn What Probiotics are and What They Do

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    Learn what science says about probiotics, digestive health and immunity. Then find the fermented foods and beverages, or supplements that are right for you.

    You’ve probably heard the hype surrounding probiotics, as the foods and beverages rich in these microorganisms gain popularity. You may have seen bottles of kombucha at your local grocery store or met someone who makes their own sauerkraut, and wondered how ingesting microorganisms can improve health.

    Bacteria are commonly associated with many potential health issues. Probiotics, however, are known as “good” bacteria, “beneficial” bacteria, or “helpful” bacteria. The term “probiotic” is a combination of the Latin prefix “pro-” (meaning “for”) and the Greek noun “bios” (meaning life).

    The term "probiotic" generally refers to beneficial microorganisms living in the gut. They are naturally found in your body, but they are also found in many foods, drinks, and supplements. Read on to learn more about how probiotics work, how they affect your health, and ways you can include them in your diet.

    Probiotics: the “beneficial” bacteria

    We learn at a young age that bacteria can be harmful. Our view of the world is shaped by the knowledge that invisible germs can make us sick. It is no surprise that bacteria of all types have gotten a bad reputation.

    However, as our knowledge of the human body evolves, scientists are getting a deeper understanding of the other side of the equation: the importance of “beneficial” or “good” bacteria. In fact, the average human has just as many bacterial cells as it does human cells. You could never remove all of these bacteria from your body, and you would not want to even if you could!

    The trillions of microorganisms that call our bodies home are commonly referred to as the “microbiome.” The microorganisms that live in our digestive systems are known as the “gut microbiome.”

    There are around two dozen common types of bacteria considered probiotics, mostly in the Lactobacillus or Bifidobacterium families. These are the key types of beneficial bacteria to look out for when adding probiotics to your diet or supplement regimen, because they can support your digestive health, as well as other aspects of wellbeing.

    Trust your gut (health) and enhance immunity

    According to a 2014 report from the National Institute of Health, approximately 60 to 70 million Americans are affected by digestive diseases. This has attracted the attention of doctors and scientists trying to understand the various factors contributing to digestive health. Scientists believe that ingesting probiotics helps restore the balance between “good” bacteria and the rest of the inhabitants in your digestive system. .

    Eating fermented foods and drinking fermented beverages are simple ways to introduce lactic acid bacteria (LAB) into the gastrointestinal, or GI, tract.

    According to a study published by the National Institute of Health, the benefits of consuming probiotics include:

    • boosting intestinal tract health
    • enhancing the immune system
    • supporting healthy digestion

    As scientists develop a broader understanding of the gut biome, the antioxidant and inflammation support capabilities of probiotics, may also show meaningful health benefits beyond the stomach. One of the more emerging applications of probiotics is linked to the gut-brain connection and their potential support to stress and mood.

    Fermentation: the prehistoric process that became the latest trend

    Scientists only began studying the health benefits of probiotics recently, but fermented foods have been traditionally known for their healing properties for hundreds of years. Fermentation, which creates probiotic-rich food and drink, is a process by which bacteria and yeasts consume sugars, then expel acids, gasses, and alcohol.

    In "lacto-fermented" foods, like pickles or sauerkraut, the beneficial bacteria digest sugars and produce lactic acid, which acts as a natural preservative.

    Fermentation is a natural process that has occurred in nature since the dawn of time, long before humans harnessed it as a culinary technique. Throughout human history fermentation has been a reliable method to preserve and improve the flavor of food. Indeed, fermented foods have played a major role in the development of human culture and history.

    Incredibly, The two most common strains of beneficial bacteria found in the human digestive system are Lactobacillus acidophilus and Bifidobacterium bifidum, which are also abundant in fermented foods and beverages.

    Fermented foods: a common theme across the globe

    As you might expect from an ancient practice, fermented foods have found established places in cultures from around the world. You are probably quite familiar with a number of the most common fermented foods and drinks from around the world:

    • Yogurt is thought to have originated in Mesopotamia before spreading throughout the Middle East and the Mediterranean.
    • Kefir is a fermented milk drink similar to yogurt. It is thought to have originated in the Caucasus Mountains, before spreading across the globe.
    • Tibicos (also known as water kefir) is thought to have originated in Mexico on the nopal (prickly pear) cactus. Pulque is another Mexican fermented beverage made from the nectar of the agave plant.
    • Kombucha is a Japanese name for a drink originating in China, made by fermenting sweet tea.
    • There are countless recipes for fermented vegetables, including: pickled cucumbers from India, kimchi from Korea, and sauerkraut from Germany.

    There are also fermented foods and drinks that won’t provide you with probiotics, including beer and wine, for example. (Their alcohol content inhibits the growth of beneficial bacteria.) Uncooked sourdough is fermented, but the beneficial bacteria is killed during the baking process.

    Straight to the gut: probiotic supplementation

    If you are interested in the health benefits of probiotics, but don’t typically eat probiotic foods, consider taking a probiotic in supplement form.

    The dosing for probiotics is measured in something called “colony-forming units” (CFUs) -- the number of active cells with the potential to grow and multiply. A typical dose of a probiotic supplement will include between one and ten billion active CFUs.

    Probiotic supplements are typically found in capsule form, but are also available in tablet, liquid, and even gummy form. The most effective formulations and delivery methods for providing viable probiotic cells are still being studied and developed.

    Choosing a proven blend of bacteria strain is important, so be sure to check the labels of any probiotic supplements you buy. Lactobacillus acidophilus and Bifidobacterium bifidum are known to be the most common strains of beneficial bacteria found in the human digestive system, which makes them good choices for supplementation.


    Whether it is probiotic-packed foods or a simple supplement, increasing your intake of beneficial bacteria can promote digestive health and support your immune system. It may require some trial and error to find the foods that please your palate, but your stomach will thank you!

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    Dr. Carla Montrond Correia ND, CNS
    Medical Content Manager
    Dr. Montrond-Correia is a licensed naturopathic physician and a certified nutrition specialist (CNS). She holds degrees from University of Bridgeport, Georgetown University, and University of Saint Joseph, and supplemented her education with internships in the health and wellness space. She's focused on research, herbal medicine, nutrigenomics, and integrative and functional medicine. She makes time for exercise, artistic activities, and enjoying delicious food.
    Our Editorial Staff
    Freelance Contributor
    The Care/of Editorial Team is made up of writers, experts, and health enthusiasts, all dedicated to giving you the information you need today. Our team is here to answer your biggest wellness questions, read the studies for you, and introduce you to your new favorite product, staying up to date on the latest research, trends, and science. Each article is written by one of our experts, reviewed both for editorial standards by an editor and medical standards by one of our naturopathic doctors, and updated regularly as new information becomes available.