Why plant variety matters

It's the Range of Plants That Counts, Not Just the Amount

The evidence here is moderate, resting on one of the largest citizen-science microbiome studies ever run, though it has real limitations worth naming honestly.

The American Gut Project analysed stool samples and dietary habits from over 10,000 volunteers across the US, UK, and Australia.

Its most widely cited finding wasn't about eating more plants. It was about eating more different kinds of them.

Diversity of plants mattered more than any single diet label

People who reported eating more than 30 different plant types a week had significantly more diverse gut bacteria than those eating 10 or fewer, along with higher levels of the short-chain fatty acids gut bacteria produce through fermentation.

What stood out was what didn't matter. Whether someone identified as vegan, vegetarian, or an omnivore made far less difference to their microbial diversity than how many different plants they actually ate.

This reframes the usual dietary question. It isn't really "animal versus plant" that predicts a diverse gut community. It's the sheer range of different plants someone eats, whatever else is on the plate alongside them.

Source: American Gut: an Open Platform for Citizen Science Microbiome Research

Why range matters more than volume, mechanistically

Different plants contain different types of fermentable fibre, and different gut bacteria are specialised to break down different fibre types. A single vegetable, eaten in large quantities, still only feeds the specific bacteria equipped to use its particular fibre structure.

Widening the range of plants eaten, herbs, spices, grains, legumes, nuts, and seeds all count alongside fruit and vegetables, gives more bacterial species something they're specifically suited to ferment, rather than concentrating all the fuel on whichever few species can use one dominant fibre type.

This is the same underlying logic seen in the Hadza hunter-gatherer studies, where a diet built around a wide range of wild plants produces some of the most diverse gut microbiomes recorded anywhere.

Source: Diversity for Your Microbiome: Eating 30+ Plants a Week

The number 30 deserves an honest caveat

The 30-plants figure comes from a single self-reported survey question, asking people roughly how many plant types they ate, not from carefully measured, verified dietary records.

Every plant counted equally in that count too, whether it was a large helping of lentils or a pinch of dried thyme in a sauce. That's a real limitation, and worth stating plainly rather than treating 30 as a precise scientific threshold.

None of that undermines the underlying finding though. The genuine, repeatable signal is that variety itself, not any specific number, tracks with a more diverse gut community. Thirty is a useful rough target, not a hard scientific cut-off.

Source: Why plant diversity matters, but counting to 30 might not

What this means for you

There's no need to count plants precisely or hit an exact weekly number to benefit from this. The honest takeaway is simpler: variety itself, across fruit, vegetables, grains, legumes, nuts, seeds, and herbs, is what this research ties to a more diverse gut community, more so than the total quantity eaten or whether meat is included. A varied, plant-rich diet is exactly what this research points toward. That's the same idea behind GutLab, everyday gut health starts with regularly feeding the microbiome a broad range of plant-rich ingredients.