How probiotics work, and the details of the probiotic strains

How probiotics work, and the details of the probiotic strains

Would you believe your intestinal tract is teeming with millions of microorganisms? Known collectively as microbiome, the various species of bacteria and fungi that live in your gut play an important role in many bodily functions. “The bacteria in the microbiome help digest our food, regulate our immune system, protect against other bacteria that cause disease, and produce vitamins including B vitamins 12, thiamine and riboflavin, and vitamin K, which is needed for blood coagulation.”1

Good health depends on maintaining diverse microbiomes in the gut as well as a proper ratio among the various species. Certain factors can disrupt the healthy composition of the gut ecosystem such as, antibiotics, illness, stress, aging, and bad dietary or lifestyle habits. An imbalance of the gut bacteria, called dysbiosis, can lead to a number of chronic diseases. 

The goal of probiotic supplements is to introduce a large number of live, beneficial bacteria back into the intestinal system to restore the proper balance. However, when choosing a probiotic, it’s important to understand that the number and variety of strains differs between products. “Health benefits are strain-specific, and not all strains are necessarily useful…”2

How different strains of probiotics can benefit you

Probiotics work by “resetting” the microbiome in the gut after it has become disrupted. “The seven core genera of microbial organisms most often used in probiotic products are Lactobacillus, Bifidobacterium, Saccharomyces, Streptococcus, Enterococcus, Escherichia, and Bacillus.”3 All of these strains have the potential to treat specific health conditions, but not every strain can treat the same problem. 

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For example, one study examined the use of probiotics in people who were taking an antibiotic and developed a side effect called antibiotic-associated diarrhea (AAD). The study concluded that specific strains of probiotics were effective in treating the disorder. “Overall, the available evidence suggests that starting treatment with Lactobacillus rhamnosus GG or Saccharomyces boulardii within 2 days of the first antibiotic dose helps reduce the risk of ADD…”4 If you’re suffering from AAD and you take a probiotic that doesn’t contain these strains, you may not notice any relief in your symptoms.

Other studies examined the effectiveness of probiotics in treating atopic dermatitis (eczema), an inflammatory skin disorder that affects up to 20% children. The results indicated that probiotics specifically containing Lactobacillus strains reduced the severity of the disease in infants and children under the age of three. “They found a significant decrease in the Scoring Atopic Dermatitis (SCORAD) index among those who received probiotics.”5

Recent research conducted in China supports the use of probiotics in patients with COVID-19.1 Some patients with COVID-19 participating in the study presented with intestinal dysbiosis; specifically, decreased levels of Lactobacillus and Bifidobacterium. The scientists in the study recommended that patients be treated with probiotics to regulate the balance of intestinal microbiota, which would therefore reduce the risk of secondary infections. 

How do I choose the right probiotic?

So do you need to research every strain of bacteria used in probiotic supplements to find exactly which one you need? No need. In general, choosing a probiotic from a reliable source that contains a broad variety of strains is a good way to ensure its overall effectiveness.


The Human Microbiome , 
Health benefits of taking probiotics , 
Probiotics , Probiotics, 
Probiotics , Probiotics, 
Can probiotics help kids with atopic dermatitis?, 
Management of Corona Virus disease-19 (COVID-19): The Zhejiang Experience , 

NOTE: The Center for Ecogenetics and Environmental Health, University of Washington and Harvard Health Publishing, Harvard University and The U.S. Department of Health & Human Services, The National Eczema Association and Journal of Zhejiang University, Medical sciences, have not reviewed or approved the above article.