Field notes
As of Oct 2026 · 1 study · newest 2025 Vegan
New: Fackelmann 2025, 21,561 people
01
The short version
Gut microbes tell vegans, vegetarians and omnivores apart in one large study of 21,561 people in 5 cohorts. Several microbes are lower in vegans, among them Streptococcus thermophilus, a dairy microbe. Whether the differences come from the diet itself, and whether they matter for health, hasn't been shown.
02
What studies have seen
Each line is one finding. The word says how many separate groups of people showed it.Gut microbes told vegans, vegetarians and omnivores apart, in each of 5 cohorts; vegans and omnivores most clearly on average.
omnivores vs vegetarians: 5 of 5 cohorts · omnivores vs vegans: 5 of 5 cohorts · vegetarians vs vegans: 5 of 5 cohorts · 21,561 people · Italy, UK, US Fackelmann 2025
[Ruminococcus] torques is highest in omnivores, then vegetarians, then vegans.
omnivores vs vegetarians: 5 of 5 cohorts · omnivores vs vegans: 5 of 5 cohorts · vegetarians vs vegans: 5 of 5 cohorts · 21,561 people · Italy, UK, US Fackelmann 2025
Streptococcus thermophilus, a dairy microbe, is higher in omnivores and vegetarians than in vegans.
omnivores vs vegans: 5 of 5 cohorts · vegetarians vs vegans: 5 of 5 cohorts · 21,561 people · Italy, UK, US Fackelmann 2025
Alistipes putredinis is higher in omnivores than in vegetarians or vegans.
omnivores vs vegetarians: 5 of 5 cohorts · omnivores vs vegans: 4 of 5 cohorts · 21,561 people · Italy, UK, US Fackelmann 2025A difference is an association: it doesn't mean a diet changes these microbes, or that they affect health. Each person was measured once.
03
Ideas being tested
What researchers think might explain it, and how far each idea has been tested.Idea · The authors suggest
The authors suggest that some of these microbes may come from food itself: several overlap with microbes found in food, such as dairy microbes in omnivores and vegetarians and soil microbes in vegans.
How far it’s been tested ProposedIn a dishIn animalsSeen in peopleTested in a trial Fackelmann 202504
What nobody knows yet
Open questions, as the studies leave them.- Q1Whether changing diet changes these microbes: each person was measured once.
- Q2How much comes from the diet itself, and how much from other habits that vegans or vegetarians share.
- Q3Smaller differences between vegetarians and vegans: only 1,744 people were in that comparison.
05
Who's been studied
WhereItaly · UK · US
How many1 study · 21,561 people
HowEach person measured once
3 of the 5 separate groups of people behind these studies are in cohorts run by ZOE Ltd.
06
The microbes
07
The studies
Each person measured once · Shotgun sequencing
Per-microbe tables open · CC BY 4.0 Competing interests Several authors have ties to ZOE Ltd, a nutrition company: two co-founded it, others are or were employees or consultants, and ten receive ZOE share options. 9 authors list ZOE Ltd. among their affiliations.