Vegetarian diets, plant-based but allowing eggs and dairy, sit between vegan and regular eating, and the gut bacteria research reflects that middle position clearly, sharing a lot of ground with vegan findings while showing its own distinct marker.
The largest dataset available
The same 21,561-person study covering vegan, vegetarian, and regular diets found gut bacteria profiles could tell these three eating patterns apart with strong accuracy. Vegetarian and vegan gut signatures overlapped a lot and were both linked to favorable heart and metabolic markers, while red meat specifically drove a distinct pattern in regular eaters linked to less favorable outcomes.
A specific, well-replicated marker
A study comparing 23 long-term vegans and vegetarians against 51 regular eaters found significantly lower levels of a compound called TMAO in the plant-based group, and crucially, even when directly challenged with a compound found in meat, vegans and vegetarians still made less TMAO. TMAO gets made when certain gut bacteria process compounds found in red meat, and it's been linked to heart disease risk.
Vegetarian and vegan are more similar to each other than to regular eating
Research directly comparing all three groups has consistently found only small differences between vegan and vegetarian gut bacteria specifically, with the bigger gap sitting between plant-based eating broadly and regular, meat-inclusive eating.
The finding that changes the whole picture
A 2025 study found something that reframes the vegetarian-versus-omnivore question entirely, regular eaters who ate a genuinely wide variety of vegetables, fruits, nuts, seeds, and beans had gut bacteria profiles comparable to vegetarians and vegans. The benefit tracked with plant food variety itself, not strictly with cutting out meat.
If you're vegetarian, the TMAO finding is a genuine, well-replicated benefit worth knowing about specifically. As with vegan eating, prioritize actual fiber and plant variety rather than assuming vegetarian status alone gets you optimal gut health. If you eat some meat but want to improve your gut health without fully cutting it out, the 2025 research above offers real reassurance, maximizing plant variety may matter more than the presence of occasional meat.
This content is for educational purposes only and is not a substitute for professional medical advice.