Probiotics

•RCT evidence— Strain-specific; common-cold and AAD strongest

The framing

"Probiotic" is a regulatory category, not a single therapy. Effects depend on:

• Species and strain (e.g. Lactobacillus rhamnosus GG vs. generic LGG).
• Dose (CFU at time of consumption, not at manufacture).
• Condition treated.
• Host microbiome (some hosts are "permissive", others reject).

Suez et al. (2018) showed that probiotic colonisation is highly person-dependent, and that probiotics actually delayed microbiome recovery after antibiotics in some hosts.

Strain-condition pairings with reasonable evidence

Condition	Strain(s)	Evidence
Antibiotic-associated diarrhoea	Saccharomyces boulardii; L. rhamnosus GG	Strong meta-analysis
C. difficile prevention	S. boulardii	Moderate
Acute infectious diarrhoea	L. rhamnosus GG	Moderate
Atopic dermatitis (infant)	L. rhamnosus GG (maternal/infant)	Modest
IBS	VSL#3 / mixed strains	Modest
Common cold duration	Mixed strains	Small

For "general aging support" the evidence is weak.

Akkermansia muciniphila

A newer focus — A. muciniphila (pasteurised, marketed as A2-Akkermansia) showed in a 3-month French RCT modest improvements in insulin sensitivity, liver enzymes, and weight in metabolic syndrome. Promising but preliminary.

Whole-food alternative

Diverse fermented foods (yoghurt, kefir, kimchi, sauerkraut, miso) deliver a richer mix of organisms than most capsules and were shown in the Stanford Sonnenburg-lab study to increase microbiome diversity and reduce inflammation markers — more than a high-fibre diet matched for calories.

Related entries

Fermented foods, Dysbiosis, Prebiotic fibre.