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What Are Probiotics? Here's What To Know About These Mood-Boosting Gut Bugs

Darcy McDonough, M.S.
mbg Nutrition & Health Writer
By Darcy McDonough, M.S.
mbg Nutrition & Health Writer
Darcy McDonough is the Senior Manager, SEO & Content Strategy at mbg. She has a master’s degree in nutrition interventions, communication, and behavior change from the Tufts Friedman School of Nutrition Science and Policy.
Image by Martí Sans / Stocksy

Probiotics are everywhere lately. And we don't mean that in the "microscopic bacteria is all around us" kind of way. You can now find everything from granola to chips that have been sprinkled or infused with a dose of good-for-your-gut probiotics. They have even invaded our beauty cabinets and cleaning products.

Since they are credited with everything from preventing chronic disease to boosting weight loss, who can blame us for wanting to cram probiotics into everything imaginable—but what exactly are probiotics, and why are they so good for us and our gut?

What are probiotics?

Probiotics are living organisms that protect the gut, or GI tract, and contribute to overall well-being. In fact, you have trillions of these friendly microscopic "bugs" in your gut and throughout your body right now. It has been estimated that our bodies host just as many microbes as human cells1. Yup, you read that right—you are made up of at least half bacteria. Each person has a unique ecosystem of microbiota, and the diversity of strains can change over the course of a lifetime or even just a few days.

The immune-boosting role of probiotics in the body.

But wait, isn't bacteria what makes us sick? Yes and no. Some bacteria are friendly—these are the ones we call probiotics. Probiotics are the good guys, stimulating and communicating with the immune system2 to keep it strong (a large portion of your body's immune tissue is actually located in the digestive tract, so it's heavily influenced by the bacteria living there). Probiotics "prime" the immune system, keeping it alert to harmful bacteria, and join in the fight by producing toxins to ward off "bad" bacteria. So, they actually work with our body to keep it healthy.

Of course, some bacteria are unfriendly as well. Unfortunately, you can't avoid bad bacteria; it's everywhere. But that's OK—the presence of some bad bacteria can help keep probiotics on their toes and in fighting shape, thus bolstering the immune system further. The key to staying healthy is for the good bacteria—probiotics—to outweigh the bad. Infections, antibiotics, stress, and diet can upset the balance of good and bad bacteria in our gut, wreaking havoc on the digestive system, immune system, and possibly even messing with your mental health. When people talk about improving their gut health, they are referring to maintaining a healthy ratio of good to bad bacteria. 

Other health benefits of probiotics.

Beyond basic immune functions, probiotics also help with digestion3. You've probably heard that fiber is good for you, but did you know our bodies cannot actually break it down? That's where the microbiome and probiotics come in. Gut bacteria feed on the fermentable fiber we eat, sometimes called prebiotics, which are found in many fruits and vegetables such as bananas, oats, and garlic. As the probiotics digest these prebiotics, they release important minerals and produce short-chain fatty acids4, which we can absorb and use. The production of short chain fatty acids is especially important because we cannot make them ourselves and they play a crucial role in reducing inflammation, maintaining the integrity5 of the gut lining (thus helping prevent leaky gut), appetite regulation, and brain signaling.

While the science is still emerging, there is growing interest in how these bacteria interact with, communicate with, and influence other systems in the body. Studies have shown that the microbiome is directly connected to the brain through the gut-brain axis6. In fact, the gut is responsible for producing up to 90 percent of our serotonin, an important brain neurotransmitter sometimes called the "happiness hormone." Additionally, there is a gut-skin axis7 that can regulate skin conditions like acne and eczema.

These two axes show how maintaining a healthy gut can have far-reaching benefits. From the obvious benefits of preventing diarrhea and relieving constipation to the more surprising acne-clearing, mood-boosting, and brain health perks, it is clear that good probiotic bacteria and gut health are integral to overall health.   

3 ways to populate your gut with probiotics.

So, how can you ensure your gut is populated with the right kind of bacteria to keep you healthy? You've got a few options:

1. Eat naturally probiotic-rich foods.

Gut health specialist, best-selling author of Happy Gut, and mbg Collective member, Dr. Vincent Pedre advises, "One way to repopulate your gut with probiotics to restore harmony and get all their many benefits is with the right foods, which can support the growth and proliferation of good bacteria that crowd out the bad ones." And the good news is you are probably already eating several delicious, gut-friendly foods like yogurt and kombucha.

Eating fermented foods is the best way to pack a probiotic punch. Fermentation is the process by which yeast and bacteria break down the sugars in a food, releasing alcohol, gas, or acids. This is what turns cabbage into kimchi, milk into yogurt, and tea into kombucha. The process encourages the growth and proliferation of bacteria, and the end result is a probiotic-rich, good-for-your-gut food. Since these foods contain probiotics, you are adding to the population of friendly bacteria in your gut when you eat them, tipping the balance in your favor.

Some probiotic-rich fermented foods include:

  • Yogurt
  • Cultured cottage cheese
  • Miso paste
  • Tempeh
  • Kimchi
  • Sauerkraut
  • Kombucha
  • Kvass
  • Kefir
  • Lacto-fermented pickles and vegetables

2. Pop a probiotic supplement.

Another great way to ensure you are getting enough probiotics to support your gut is through probiotic supplements. These capsules contain billions of colony-forming units (CFUs) of freeze-dried bacteria. By taking a probiotic supplement, you are delivering an array of friendly bacteria right to your gut and inviting them to make a home there.

However, Dr. Pedre offers a word of caution: "With probiotics, it's all about survival. These delicate microorganisms must survive several obstacles: the manufacturing process, shelf life, and (once you take them) the acid in your stomach environment to reach your intestines, where they do their job."

So be sure to seek out trustworthy brands with third-party verification for survivability. In the past, probiotics have required refrigeration to help with survivability, but more and more shelf-stable probiotics have come to market in recent years. In fact, in a 2019 trend report, Whole Foods predicted that we'll be seeing a lot more probiotics leaving the refrigerator this year.

3. Increase your fiber intake.

Lastly, fiber can help increase the population of probiotics in your gut. As a prebiotic, it plays an important role in gut health. As we mentioned above, probiotics eat prebiotics. Therefore, by eating prebiotic-filled fiber you are essentially feeding the bacteria in your gut and encouraging their proliferation and survival. Think of your microbiome like a pet. It needs to be fed daily. Even if you are eating tons of fermented foods and popping a daily probiotic pill, those good bacteria won't stick around in your gut if there is nothing to eat.

For a happy gut, incorporate lots of fiber-rich fruits, vegetables, and grains into your diet, along with fermented foods like yogurt and kefir.   

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Darcy McDonough, M.S. author page.
Darcy McDonough, M.S.
mbg Nutrition & Health Writer

Darcy McDonough, M.S., is the Senior Manager, SEO & Content Strategy at mindbodygreen. She holds a master’s degree in nutrition interventions, communication, and behavior change from Tufts Friedman School of Nutrition Science and Policy. She has previously worked in nutrition communications for Joy Bauer, the nutrition and health expert for NBC’s TODAY Show.

McDonough has developed & lead nutrition education programming in schools. She’s covered a wide range of topics as a health & nutrition reporter from the rise in the use of psychedelics for depression to the frustrating trend in shorter doctors' appointments and the connection between diet and disease.