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. 
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
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.
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.
Immune SystemYour small intestine contains the largest density of immune cells in your body . 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. [10, 11]
Inflammation 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,  and cardiovascular disease. [13, 14]
Nutrient Absorption Inflammation also damages the lining of the digestive system.  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.
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.
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.
Leuconostoc mesenteroidesLactobacillus brevisPediococcus pentosaceusLactobacillus plantarum
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 blends
Saccharomyces 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. [106 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.
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. [107 Trusted SourcePubMedGo to source, 108 Trusted SourcePubMedGo to source]
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. [110, 111, 112]
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)
Probiotics are safe and have few side effects. The National Institute of Health states that probiotics are generally safe, even for premature infants. 
“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.” 
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.
Use for reference links. Use Pubmed citation NOT just URL when available
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