This 2021 review subject was probiotic bacteria survival and colonization:

“Health benefits of probiotics are diminished due to substantial reduction of viable probiotic bacteria under harsh conditions in the gastrointestinal tract and colonization resistance caused by commensal bacteria. This review illustrates the journey of probiotics from oral administration to the gastrointestinal tract, followed by colonization of the gut, with a particular focus on the adhesion process of probiotics on mucosa or intestinal epithelial cells.

• Mouth – influence of saliva on survival rates of probiotics seems to be minimal.
• Stomach – transit takes between 5 min and 2 h. Prolonged exposure to the acidic environment is a huge challenge for probiotics.

• Small intestine – bile acids and digestive enzymes (including lipases, proteases, and amylases) can impact probiotic viability through cell membrane disruption and DNA damage.
• Colon – probiotics compete with host microbiota for nutrients and adhesion sites to colonize colonic mucosa and proliferate. Due to colonization resistance, most probiotics are excreted so that they cannot be detected.

Composition of gut microbiota is highly variable. Microbial composition is considerably different between people in different geographic locations and with different diets.

Probiotics cannot change intestinal microbiota community structure or diversity.

How probiotics communicate with commensal bacteria and some are successfully introduced to gut microbiota is of great interest. Understanding these factors will facilitate employment of effective delivery strategies designed for probiotics to overcome colonization resistance and achieve health benefits.”

https://www.frontiersin.org/articles/10.3389/fcimb.2021.609722/full “Probiotic Gastrointestinal Transit and Colonization After Oral Administration: A Long Journey”

This review provided details supporting points 2 and 6 of Harnessing endogenous defenses with broccoli sprouts:

“Even though probiotics as food or supplements demonstrate favourable clinical outcomes, they typically don’t colonise the gut. How do we expect them to restore diversity and lost species to the gut microbiome after antibiotics? If no trace of an administered probiotic organism can be found a few weeks later, is there any sustained benefit?

If the gut can harbour around 1,000 different species, why do we expect a probiotic supplement harbouring just a few species to favourably modify a human microbiome?”

That paper’s emphasis was reflected in its title, “Restoring Gut Ecology: Harnessing the Inbuilt Defence Mechanisms of the Gut Epithelium.”

I stopped taking probiotics earlier this year after 16 years of twice-daily intake. I’ve increased prebiotic intake. Pretty soon I’ll find out whether my innate and adaptive immune systems have changed enough to ward off spring allergy-season effects.

Sand sculptures