Probably the most
oversold phrase in food.
Gut health sells a great many things, most of which have no business claiming it. That is a shame, because underneath the marketing sits some genuinely interesting science — and a couple of things you can act on that cost nothing.
This page explains what the gut microbiome is, what the evidence actually supports, and where it thins out. No prior knowledge assumed, and no pretending we know more than anyone does.
You are outnumbered
in your own body.
There are more microbial cells living in and on you than there are human cells making up the rest of you, and the greatest concentration by far sits in your large intestine. For most of medical history they were assumed to be irrelevant, or mildly unwelcome. It turns out they finish digesting what you cannot, produce compounds your own cells depend on, and hold a continuous conversation with an immune system that has stationed a great deal of itself in your gut wall. What you feed them changes who thrives.
30–45 days
45–90+ days
Thirty a week,
five in a punnet.
There is one target worth remembering in this whole subject, and it is not a supplement dose.
What the gut microbiome actually is
Your large intestine is home to trillions of microorganisms — mostly bacteria, along with fungi and viruses. Collectively they are called the gut microbiome, and there are more of them than there are cells in the rest of you.
They are not passengers. They finish digesting things your own body cannot break down, particularly plant fibre. They manufacture certain vitamins. They occupy space that less welcome organisms would otherwise take, and they are in constant conversation with your immune system — a large proportion of which is stationed in the gut wall, precisely because that is where the outside world gets closest to the inside of you.
Everyone's is different. Yours is shaped by how you were born, what you ate as a child, where you live, medication you have taken and, importantly, what you eat now — which is the only part still in your hands.
Why fibre is the thing that matters most
Fibre is plant material you cannot digest. That sounds like a flaw until you realise it is the point — it arrives in the large intestine intact, and that is what your microbes eat.
When they ferment it, they produce short-chain fatty acids, of which butyrate is the best studied. Butyrate is the preferred fuel of the cells lining your colon. They are, quite literally, fed by the by-products of your own bacteria digesting your dinner.
This is the least glamorous and most solid part of the whole subject. No supplement replicates it. You have to eat plants, and different ones, because different fibres feed different bacteria.
Why variety beats quantity
Eating a great deal of one vegetable is not the same as eating a little of many. Different plants carry different fibres and different polyphenols, and different bacteria specialise in different things. Feed a narrow range and you cultivate a narrow population.
This is where the thirty-plants figure comes from, and why it counts herbs, spices, nuts, seeds and grains rather than only vegetables. A teaspoon of something is still a different plant.
It is also, frankly, why we sell a mix. Five varieties in one punnet is five plants, not one.
Where fermented food fits
Fermented food arrives with live microbes already in it, and with the food itself partly broken down.
The Stanford trial we describe on our fermentation page found that ten weeks of a fermented-food diet increased gut microbial diversity and lowered inflammatory markers — while a high-fibre diet, over the same period, did neither. That surprised the researchers too.
It does not make fermented food better than fibre. Most likely they do different jobs, and the interesting question is what happens when you do both.
Wastyk et al., Cell, 2021
What actually disrupts it
Worth knowing, because it is more useful than any list of superfoods. Antibiotics, which do not discriminate between the bacteria you want and the ones you do not. A diet narrow in plants. Very low fibre intake. Significant, sustained stress. Poor sleep.
Most of that list is either unavoidable or hard to change quickly. Which is precisely why the part you can influence — eating a wider range of plants — is worth the attention.
30
different plants a week — the single most useful target to come out of gut microbiome research.
In 2018 the American Gut Project, a citizen-science study spanning the US, UK and Australia, compared people eating more than thirty different plant types a week with those eating ten or fewer. The high-variety group had noticeably more diverse gut microbiomes, and fewer antibiotic resistance genes.
The important word is different. Not thirty portions — thirty kinds. Herbs count. So do spices, nuts, seeds, grains, pulses and, yes, five varieties of microgreen in one punnet.
It reframes the task rather usefully. Most people trying to eat better attempt to eat more vegetables, which is effortful. Eating a wider range is easier, cheaper and rather more interesting.
What nobody
can tell you.
This is the corner of nutrition with the loudest claims and the thinnest proof. Here is where we stop.
How strong is the '30 plants' evidence, really?
Worth being straight about, because the figure is quoted everywhere as though it were settled law.
It comes from the American Gut Project, a large citizen-science study published in 2018. People eating more than thirty different plants a week had more diverse gut microbiomes than those eating ten or fewer. The comparison groups at the extremes were small — dozens of people, not thousands — and it is observational, so it cannot prove the plants caused the diversity rather than simply travelling with a generally better diet.
What it is, is a useful and memorable target that points in a direction the wider evidence supports. What it is not, is a precise dose. Nothing happens at twenty-nine.
Is a diverse microbiome definitely better?
Generally it is associated with better health outcomes, and that association is consistent enough to be taken seriously. But diversity is a crude measure — it counts how many different species are present, not whether they are the right ones or what they are doing.
Researchers do not yet agree on what an ideal microbiome looks like, and it almost certainly differs between people. Anyone offering you a definitive answer on that is ahead of the science.
Can you tell me what this will do for my gut?
No, and we would be suspicious of anyone who could. Your microbiome is specific to you, and the response to any change in diet varies enormously between individuals — which is one of the more robust findings in the field.
What we can say is what our products are: plants, several different kinds, some of them fermented with live cultures. Whether that shifts anything measurable in you, only you will find out — and 'my digestion feels calmer' is a perfectly reasonable thing to go on.
Should I be taking a probiotic supplement instead?
That is a conversation for a pharmacist, GP or registered dietitian rather than a microgreen farm, and it depends entirely on your situation — there is decent evidence for specific strains in specific circumstances.
What we would say is that food and supplements are not competing. Our position is simply that eating a wider range of plants is the part with the longest track record, and it is the part we can help with.
If I have a diagnosed gut condition, is this suitable?
Please ask your clinician first. Some conditions require a low-fibre or low-FODMAP approach, at least temporarily, and general advice about eating more plants can be exactly the wrong thing.
Our fermented products are also unpasteurised and contain live cultures, which matters if you are immunocompromised. We would far rather you checked than assumed.
Read it
yourself.
Links go to the original research rather than to somebody's summary of it.
A handful of plants,
without the shopping.
Fusion Mix is five different microgreens in one punnet — five of your thirty, cut the day it goes out. Big Shot is the same five, fermented, in a ten-second shot.
See what we grow →