The tree · Inflammation and the body's messaging
Gut microbes from a young animal rejuvenate an old one
The community of microbes in the gut changes with age, and the change is thought to feed the low-grade inflammation of old age through a leakier gut wall. The direct test is to swap the microbes: in 2022 a Norwich group transferred gut microbes from young mice into old ones and found the old mice's gut lining, eyes and brain inflammation shifted toward young, and the reverse transfer aged young mice. Transferring gut microbes from one person to another is already an approved treatment, since 2022, for a dangerous gut infection; nobody has shown it does anything for ageing in people, and the leaf asks for that.
What would count
An old living animal given gut microbes from a young one afterwards has measurably less inflammation or better tissue function than untreated old controls, in a peer-reviewed report. The first-human rung needs a controlled trial in which older people given a defined microbial transfer improve on an age-related measure more than placebo. For the clinic rung: a regulator approves such a transfer for an age-related condition.
Who settles it: Peer-reviewed reports; the regulator's approval record for the clinic rung.
Where it stands
Shown in animals. Reached 29 April 2022, on the record of doi.org. Next rung more than 20 years away, if ever.
When it reaches the clinic: the project's estimate
This is the one thing on this page that is a judgment rather than a record. The project's estimate of the year it reaches the clinic is 2050, no earlier than 2035 and no later than not this century; the model draws from that range every run, with the likely year the most probable draw. Set 16 October 2026, a first pass awaiting an outside review.
| Rung | No earlier than | Most likely | No later than | |
|---|---|---|---|---|
| First human | 2029 | 2033 | 2060 | |
| In clinical use | 2035 | 2050 | not this century | feeds the year at the top |
Why. A transfer product exists and is approved for an infection, so a trial in older people is cheap to run; what is missing is any human sign that it touches ageing. The likely year assumes a controlled trial in frailty or vaccine response reports positive in the early 2030s and an approval for an age-related condition follows around 2050; the earliest assumes a trial already running in older adults reports positive by 2029; the latest allows for the mouse result not carrying to people.
Changes to this record
None since it was written on 16 October 2026. Every change to the stage or the estimate lands here with its date, the old value, the new one and the reason, and a change to the estimate never happens because a number looked wrong: it needs a dated reason and a source.
The last readings
- 17 October 2026 Quiet
Nothing in the window. No controlled trial of a microbial transfer in older people has reported, and no new animal report dated 2026-10-10 to 2026-10-17 was found. Two registered trials bear on the first-human rung and are already allowed for by the estimate's assumption of a trial running in older adults: ARMOR (ClinicalTrials.gov NCT06649981, registered 2024-10-21, capsules of gut microbes from young active donors or placebo in 65 to 84 year olds in Chile, with its protocol published in BMC Geriatrics volume 26 in 2026) and STEP-aging (NCT05598112, oral transfer for ageing at Fuwai Hospital in China, recruiting, primary completion estimated 2026-12-31). Neither has results, and whether either registry entry changed in the window could not be checked because the registry could not be opened from this session.
What the story so far says about it
No promise, self-experiment or logged paper names this one yet.
Notes
The gut's microbes are one of the three published kinds of ageing damage ("hallmarks") the branch groups, and this is the only leaf for it; a drug or diet that changed the microbes with a measured effect on ageing in people would belong here too, and none has such a record.