What Are Probiotics? Your Guide to Healthy Gut Bacteria

Probiotics Defined

What are probiotics: Hands holding intestine illustration

Probiotics are live microorganisms that live in your digestive tract and confer health benefits when consumed. They can be obtained through foods (sauerkraut, kombucha, miso, kimchi, etc.) or via probiotic supplements.  

What Are Probiotics Good For?

Probiotics are important for maintaining the health of your microbiome, the complex ecosystem in your digestive system that includes around 300 to 500 bacterial species. These microorganisms perform critical functions for your digestion, hormones, nervous system and immune system. [1]

The balance of healthy and harmful bacteria in your gut have far-reaching consequences for your health. Gut dysbiosis is an imbalance of microorganisms in your digestive system, much like a garden overrun with weeds. Dysbiosis doesn’t just lead to digestive symptoms, but it can negatively impact mood, energy, skin, joint health, metabolism, sleep, immune function, hormone balance, thyroid function and more.

The good bacteria in probiotics can help to restore and maintain balance in your gut microbiota — the world of bacteria in your gut — and thus, it can help with many different symptoms and conditions.   

Why We Need Probiotics More Than Ever

Hand in rubber glove holding soapy sponge

People in traditional societies had far more exposure to live bacteria than most of us do today. Natural childbirth, breastfeeding, contact with animals, contact with soil, and consumption of whole and fermented foods all helped to maintain a diverse human microbiome.

Our environment is much more sterile today. We routinely diminish our exposure to bacteria through Cesarean birth, antibiotics, and the use of antibacterial soaps and cleaners. Unhealthy diets that are low in fiber and high in sugar compound the problem. Even a sedentary lifestyle and poor sleep habits can negatively impact your beneficial bacteria. [2 Trusted SourcePubMedGo to source, 3 Trusted SourcePubMedGo to source]

In today’s world, bacterial imbalances in the digestive tract are the norm.  

How Do Probiotics Help You?  

Probiotics help to improve the balance of organisms in your gut, [4 Trusted SourcePubMedGo to source, 5 Trusted SourcePubMedGo to source, 6 Trusted SourcePubMedGo to source] reduce overzealous immune system activity, [7 Trusted SourcePubMedGo to source, 8] Trusted SourcePubMedGo to source and reduce inflammation in the gut and elsewhere in the body. [9 Trusted SourcePubMedGo to source, 10 Trusted SourcePubMedGo to source] Probiotics are also antibacterial, antifungal, and antiparasitic and help to eliminate bad bugs.

When you understand the connections between your gut health, your immune system, inflammation, and nutrient absorption, it’s easier to appreciate the far-reaching impact of your gut health.

What Are Probiotics? Your Guide to Healthy Gut Bacteria - image7

Immune System
Your small intestine contains the largest density of immune cells in your body [11].  This is one reason why the health of your digestive tract and the health of your immune system are so closely linked. If your gut bacteria are unbalanced, your immune system may be chronically activated into an overzealous response. [12, 13]

An overzealous immune system produces inflammation in the gut and elsewhere in the body. Chronic inflammation is a major factor in many health conditions, including rheumatoid arthritis, [14] and cardiovascular disease. [15, 16]   

What Are Probiotics? Your Guide to Healthy Gut Bacteria - image1
What Are Probiotics? Your Guide to Healthy Gut Bacteria - image4

Nutrient Absorption
Inflammation also damages the lining of the digestive system. [17] This can impair nutrient absorption. If you eat a healthy diet but don’t absorb nutrients well, this can be similar to eating an unhealthy diet.

What Are Prebiotics and Synbiotics?

Prebiotics are the fiber-rich foods that feed gut bacteria. If your gut is in good health, a diet rich in prebiotic foods can be very beneficial. However, it’s important to note that prebiotics may cause problems for some. That’s because prebiotics also feed bad gut bacteria.

Some patients with gut issues may actually need to restrict their intake of prebiotics. The low FODMAP diet is designed to restrict prebiotic foods and can be very helpful for patients with IBS and IBD. [18 Trusted SourcePubMedGo to source, 19, 20 Trusted SourcePubMedGo to source, 21 Trusted SourcePubMedGo to source, 22 Trusted SourcePubMedGo to source, 23 Trusted SourcePubMedGo to source, 24 Trusted SourcePubMedGo to source]

Synbiotics are dietary supplements that combine probiotics and prebiotics. While this is great for some, a synbiotic supplement may not be the best probiotic choice for people with digestive issues.

Probiotic Foods

Diet can be a great source of probiotics. However, through diet alone, it can be difficult to obtain the dosages that have been shown to be effective in research. For therapeutic doses of probiotics, dietary supplements may be a better choice.  

Here are some of the probiotic species and dosages found in probiotic foods.

FoodSpeciesAmountEquivalent Dose
SauerkrautLeuconostoc mesenteroidesLactobacillus brevisPediococcus pentosaceusLactobacillus plantarum3 billion CFUper cup1/8 capsuleLacto-Bifido Blend Probiotic
Yogurt [25, 26]Lactobacillus acidophilusStreptococcus thermophilusLactobacillus delbrueckii subsp. bulgaricus2.5 billion CFUper  cup1/10 capsuleLacto-Bifido Blend Probiotic
Lacto-fermented Pickles [27, 28]Lactobacillus caseiLactobacillus rhamnosusLactobacillus plantarumLactobacillus brevis1.3 billion CFUper pickle1/20 capsuleLacto-Bifido Blend Probiotic
Kefir [29]Lactobacillus brevisLactobacillus acidophilusLactobacillus caseiLactococcus lactisSaccharomyces cerevisiae2.5 billion CFUper cup1/10 capsuleLacto-Bifido Blend Probiotic
Kimchi [30, 31]Weissella koreensisLactobacillus sakeiLactobacillus graminisWeissella cibariaLeuconostoc mesenteroides11.5 billion CFUper ½ cup1/2 capsuleLacto-Bifido Blend Probiotic

Benefits of Probiotics for Gut Health

Probiotics are best known for their ability to help with various gut health conditions. A large volume of research supports this. 

Probiotics Support These Conditions

High level of scientific support for:
Irritable Bowel Syndrome (IBS)
Gas, bloating, diarrhea, constipation, abdominal pain
Inflammatory Bowel Diseases (IBD)
Crohn’s disease and ulcerative colitis 
Depression and Anxiety
Gut Imbalances
SIBO, H. pylori, candida/fungus, pathogens, antibiotic associated diarrhea
Leaky Gut
Gut damage and permeability
Vaginal infections, urinary tract infections, tooth decay  
Limited, but encouraging, scientific support for:
Cognitive function, brain fog
Hormonal Health
Thyroid health, PCOS, endometriosis, bone density
Dairy intolerance, seasonal allergies
Autoimmune Conditions
Type 1 diabetes, multiple sclerosis, rheumatoid arthritis 
Metabolic Health
Blood sugar, cholesterol, blood pressure, weight loss
Sleep quality and Disruption

Here are some of the research highlights:

Benefits of Probiotics for Non-Digestive Conditions

Probiotics aren’t just good for digestive health. Research has found that probiotics are effective for a number of non-digestive conditions. Probiotics:

Simplifying Probiotics 

There are a dizzying number of probiotic strains available in supplement products. However, here’s a trick to keep things simple: most every probiotic can be organized into one of these three categories: 

Lactobacillus & bifidobacterium species predominated blendsSaccharomyces Boulardii (a healthy fungus)Soil-Based Probiotics using various bacillus species 
These are the most well-researched, with over 500 trials assessing their validity.  These live microorganisms are also known as lactic-acid producing probiotic bacteria.  They typically do not colonize the host but do improve the health of the host.The second most researched probiotic, with over 100 studies.  Saccharomyces boulardii (S. Boulardi for short) is not a normal part of human microbiota, meaning it does not colonize us but does improve the health of the host.The third most researched category of probiotics is soil-based probiotics. This group has roughly 14 clinical trials evaluating their effectiveness. This category is also known as spore-forming bacteria. This category of probiotic can colonize the host. [108 Trusted SourcePubMedGo to source]

You don’t need to try every probiotic product on the market. Instead, use one quality formula from each category, and take them all together.  Wait a few weeks and reevaluate your symptoms. If you are seeing some level of improvement, keep going. If not, you can discontinue probiotic therapy and don’t need to try a different formula. 

In my clinical experience, taking all three categories together has been the difference between people experiencing minimal results or impressive results.  

What are probiotics: Three categories of probiotics needed for gut balance

Research supports this approach to taking probiotics. When mixtures of several probiotics were compared with single strains of probiotics in the treatment of IBS, the systematic reviews and meta-analyses indicated that the multi-strain probiotics were more effective than single-strain probiotics. [109 Trusted SourcePubMedGo to source, 110 Trusted SourcePubMedGo to source]

Quality Assurance 

Probiotic products are not highly regulated in the United States. Several studies have shown that a surprising number of probiotic supplements do not contain the species and concentrations listed on their label, or contain unacceptable microorganisms. [111, 112, 113]

When shopping for probiotic supplements, look for these indicators of quality:

  • A clearly stated list of species
  • A clearly stated number of colony-forming units (CFUs) in the billions
  • A manufacture date or expiration date
  • Labeled free of common allergens and other substances you may wish to avoid (e.g. gluten-free, non-GMO, vegan)
  • Good Manufacturing Practices (GMP) certification
  • Lab-verified for probiotic species and potency by third-party analysis (independent lab testing)

My line of probiotic supplements meets all of these quality assurance criteria.

What are probiotics: Three bottles of probiotic supplements

Probiotic Safety

Probiotics are safe and have few side effects. The National Institute of Health states that probiotics are generally safe, even for premature infants. [114]

“Given the large quantities of probiotics consumed around the world, the numbers of opportunistic infections that result from currently marketed probiotics are negligible. For example, probiotics have been administered to thousands of newborn infants, including some who were premature, without a single case of sepsis.” [115]

There Are a Lot of Reasons to Take Probiotics

Some medical professionals still claim that there is no evidence that probiotics are effective. Clearly these “experts” haven’t spent hundreds of hours combing through the research. 

Of course, more research is always needed to refine our understanding. And new studies into probiotics are published regularly.

With more than 500 clinical trials to support their use in maintaining gut health and treating a wide variety of symptoms and conditions, probiotics simply make sense. 

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2 thoughts on “What Are Probiotics? Your Guide to Healthy Gut Bacteria

  1. You make some good points in your article, however I question how you arrived at the conclusion with any degree of scientific rigor that one should take a probiotic from each of the three listed categories as a shotgun approach to gut issues. This is akin to throwing crap at a wall and seeing what sticks. It’s never a good idea to guess with treatment. The patient can be out both money and time. Why not get some sort of gut or other lab test instead to see what is actually going on in your gut that may be the culprit? Then one can tailor treatment to their specific issue and test result they want to influence

  2. Once again, no answer from Dr. Ruscio. He also has a massive conflict of interest with his online supplement store he always links to for your “convenience”. Keep on riding the gravy train though and ignore all the people with gut issues generalized probiotics have been useless for and have actually made their issues worse

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