From Memios
The Longevity Letter
Practical writing and video on living strong and active into your 90s. No hype, no supplements to sell. Just what the evidence supports and what it looks like on an ordinary Tuesday.
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ResearchWhat causes constipation, and why do some people get it more than others?
The evidence is strongest for the definition and for who is affected: pooled prevalence of functional constipation by Rome IV criteria is about 10% of adults, roughly twice as common in women.
2026-09-30 · 19 min read
ResearchFecal microbiota transplantation (FMT): what it treats and what can go wrong
For recurrent Clostridioides difficile infection, a Cochrane review found FMT likely leads to a large increase in resolution (RR 1.92, moderate certainty).
2026-09-30 · 12 min read
ResearchDo fermented foods change the gut microbiome?
The best-known human trial (Wastyk 2021, Stanford, 18 people per arm) found a high-fermented-food diet steadily increased gut microbiota diversity and lowered inflammatory markers over 17 weeks.
2026-09-30 · 7 min read
ResearchWhat "good" and "bad" gut bacteria actually means
The honest summary is that "good" and "bad" are shorthand for statistical associations plus a small number of mechanistic experiments, and that the same species can sit on either side of the line depending on strain.
2026-09-30 · 19 min read
ResearchIrritable bowel syndrome and the gut microbiome: is the microbiome different, do probiotics help, and what does a low-FODMAP diet do?
Limited evidence. The evidence is limited and strain-specific.
2026-09-30 · 10 min read
ResearchWhich medicines and supplements are known to cause constipation, and how often do they do it?
Where trials and meta-analyses report numbers, the size of the effect is measurable rather than theoretical: bladder anticholinergics roughly double the odds of constipation versus placebo.
2026-09-30 · 16 min read
ResearchDo probiotics help after bowel preparation or colonoscopy?
Limited evidence. Results are mixed.
2026-09-30 · 7 min read
ResearchDo probiotics or synbiotics taken during or after antibiotics help?
Pooled randomised evidence shows fewer episodes of antibiotic-associated diarrhoea when a probiotic is taken alongside antibiotics.
2026-09-30 · 14 min read
ResearchSmall intestinal bacterial overgrowth (SIBO): how is it diagnosed, how reliable is breath testing, and does rifaximin work?
Limited evidence. The evidence here is limited.
2026-09-30 · 9 min read
ResearchWhat do the trials actually show for fibre, fluid, laxatives, movement, toileting and pelvic floor training?
The 2023 joint American Gastroenterological Association and American College of Gastroenterology guideline gives its strongest recommendations with moderate certainty to polyethylene glycol.
2026-09-30 · 25 min read
ResearchHow bowel preparation for colonoscopy changes the gut microbiome, and how fast it recovers
In healthy adults, bowel prep causes an immediate large drop in bacterial load (31-fold in Jalanka 2015) and changes composition.
2026-09-29 · 7 min read
ResearchClostridioides difficile infection after antibiotics: risk by drug class, prevention and outcomes
Pooled observational data show large differences in risk by drug class, with clindamycin, fluoroquinolones and cephalosporin-type drugs carrying the highest odds and tetracyclines showing no increase.
2026-09-29 · 9 min read
ResearchWhat consumer stool microbiome tests can and cannot tell you
They are marketed as reading your gut health; the published evaluations say the analytical performance does not yet support that.
2026-09-29 · 14 min read
ResearchHow does dietary fibre affect the gut microbiome and health?
Across 64 trials, fibre supplements (especially fructans and galacto-oligosaccharides) raised stool Bifidobacterium and Lactobacillus but did not change alpha-diversity.
2026-09-29 · 9 min read
ResearchIs a more diverse gut microbiome healthier?
Low diversity or low gene richness is repeatedly associated with worse metabolic markers in population studies, and one randomised trial raised diversity with fermented foods while inflammatory markers fell.
2026-09-29 · 13 min read
ResearchHelicobacter pylori: what does it cause, how is it treated, is resistance a problem, and do probiotics help eradication?
The evidence that H. pylori causes gastritis and raises the risk of ulcer and stomach cancer is well established.
2026-09-29 · 10 min read
ResearchIntestinal permeability and "leaky gut": what is established, how it is measured, and what the supplements sold for it show
Increased permeability is a measurable finding in celiac disease and inflammatory bowel disease, and in stress states such as NSAID use and endurance exercise.
2026-09-29 · 12 min read
ResearchWhat happens to the gut microbiome during and after a course of antibiotics?
A disrupted community is measured, not felt: sequencing shows loss of diversity within 3 to 4 days of starting a drug and a shifted composition afterwards.
2026-09-29 · 7 min read