Many of us have at least a rudimentary understanding and awareness of the basics of probiotics. Not unlike other areas of medicine, and life, there are more advanced and nuanced issues that impact the specificity and effectiveness of their clinical impact. 
The International Scientific Association for Probiotics and Prebiotics defines probiotics as “live microorganisms that, when administered in adequate amounts, confer a health benefit on the host”. These microorganisms consist mainly of bacteria but also include yeasts, and are naturally present in fermented foods, but can also be added to foods and of course are available as dietary supplements.
Probiotics are not the same as prebiotics. Prebiotics are usually complex carbohydrates (such as inulin and other fructo-oligosaccharides) that microorganisms in the gastrointestinal tract use as metabolic substrates. Synbiotics are products that contain both prebiotic sugars and probiotic organisms. Then there are postbiotics. This term refers to the waste left behind after the body digests both prebiotics and probiotics. Healthy postbiotics include nutrients such as vitamins B and K, amino acids, short chain fatty acids and antimicrobial peptides that help to slow down the growth of pathogenic or disruptive bacteria.
Probiotics are identified by their specific strain, which includes the genus, the species, the subspecies (if applicable), and an alphanumeric strain designation. There are seven core genera of microbial organisms that are most often used in probiotic products and include: Lactobacillus, Bifidobacterium, Saccharomyces, Streptococcus, Enterococcus, Escherichia, and Bacillus.
Here is an example of identification: Bifidobacterium (genus) longum (species), 35624 (strain designation, Bifantis (nickname).
How do they work? The gastrointestinal tract of humans is colonized by many microorganisms, including bacteria, archaea, viruses, fungi, and protozoa. This is collectively known as the gut microbiota, microbiome, or intestinal microflora. The composition of all these microorganisms has many implications in health and disease, and not just those of the digestive system.
Oral probiotics transiently colonize the human gut mucosa, and their influence depends on the baseline microbiota, and the probiotic species/strain/potency. The mechanisms of their effects are nonspecific and genus, species, and strain specific.
These mechanisms include inhibition of the growth of pathogenic microorganisms in the gastrointestinal tract, production of bioactive metabolites, such as short-chain fatty acids, and reduction in the pH of the colon lumen. Other species-specific mechanisms can include the synthesis of vitamins, intestinal barrier effects, bile salt metabolism, enzyme activity and the neutralization of toxins. Strain-specific mechanisms include cytokine production, immunomodulation, and effects on the endocrine and nervous systems.
Understanding of the microbiome has escalated and deepened such that we now know that probiotics have wide ranging prevention and intervention effects and potential, including gastrointestinal, gynecological, mental health, skin, immunity, and autoimmunity.
Think irritable bowel syndrome, inflammatory bowel syndrome, infectious diarrhea, antibiotic associated diarrhea, atopic dermatitis, hypercholesterolemia, obesity, vaginitis, cystitis, depression, and more.
Summary
- Probiotics stand amongst the primary pillars of dietary supplementation
- A daily supplement of a broad spectrum probiotic can be simple and straight forward in low to medium doses (1 billion to 10 billion CFUs per day)
- Probiotic specificity can be utilized as part of a treatment strategy, choosing the specific genus/species/strain and potency depending on the clinical goals for that patient. A naturopathic physician, functional medicine or integrative medicine physician are in the best position to effectively recommend specific probiotic products for specific clinical situations
