There is no universally best diet. What works is plant variety.

A few years ago a story went around the internet that sounds like the ideal experiment. Two identical twins, Hugo and Ross Turner, split their diets for twelve weeks. One ate vegan, the other ate meat and dairy. Same calories, same training six times a week, same genes. The only variable was the food.

Finally a clean showdown, everyone thought. Now we’ll find out which diet wins.

We won’t. And the reason why not is far more useful than any result that could have come out of it.

What actually happened to the two of them

On the vegan diet, Hugo lost four pounds — roughly two kilos. His cholesterol dropped, his blood sugar stabilized, and he reported steadier energy through the day. At the same time he lost some muscle mass and openly admitted to a marked drop in libido. Ross, on the meat diet, gained ten pounds of muscle, but also fat — from thirteen percent to fifteen. His cholesterol stayed the same, his energy fluctuated.

And then the finding that gets quoted from the story most often: during the vegan diet, the diversity of Hugo’s gut microbiome dropped significantly. Ross’s stayed stable.

This is exactly the moment where most retellings stop and draw a conclusion. I wouldn’t.

Two people are not a sample

The experiment ran under the supervision of Tim Spector’s team at the Department of Twin Research at King’s College London, which lends it a weight it doesn’t deserve. It wasn’t a study. It never went through peer review, it was never published. It’s a well-prepared home experiment with one person in each group.

The irony is that Spector’s own team has research that explains precisely why you can’t read anything from two people.

It’s called PREDICT, and it came out in 2020 in Nature Medicine. 1,103 participants, 660 of them twins. Everyone got identical meals, and researchers measured what their bodies did with them. The result: identical twins respond to the same food dramatically differently. Variation between people was 103% for triglycerides, 68% for glucose, 59% for insulin. The inflammatory response to one and the same meal differed among healthy adults as much as tenfold.

And on the microbiome specifically: identical twins share about 34% of their gut microbes. Two random unrelated people share roughly 30%. The difference is so small it’s worth reading twice — your genes have almost no say over your microbiome.

So: the difference between two people is bigger than the difference between two diets. If you compare two diets on two people, you’re mostly measuring the people.

What a sample of 21,561 people showed

Four years later, Nature Microbiology published a paper that looked at the same question properly. Vegans, vegetarians and omnivores, 21,561 people in all.

Vegans had, on average, the healthiest microbiome profile. Then vegetarians, then omnivores. Which is the opposite of what happened to Hugo — one person against twenty-one thousand.

But the really interesting finding is subtler and almost always gets lost in the headlines: what mattered was the amount and variety of healthy plant foods, not the diet label. Omnivores came out worse mainly because they eat fewer plants. An omnivore with a varied plant intake does well. A vegan who gets by on three kinds of vegetables and processed substitutes does not — which, by the way, is the most likely explanation for Hugo’s drop in diversity.

So we don’t round it off in our own favor

It would be convenient to stop here and pretend that the type of diet doesn’t matter at all. That isn’t true, and it should be said.

In 2023, JAMA Network Open published a Stanford study by Christopher Gardner — the one you may know from the Netflix documentary You Are What You Eat. Twenty-two pairs of identical twins, 44 people, eight weeks, randomized assignment. And above all: both diets were healthy. Vegetables, legumes, fruit, whole grains, no added sugar or refined starches on either side. No hastily built straw man.

The vegan group still came out ahead — lower LDL cholesterol, lower fasting insulin, greater weight loss.

There’s a catch, and not a small one. The vegan group also ate fewer calories and lost more weight, so part of the improvement may be down to weight loss rather than veganism. Eight weeks is short for anything health-related. And healthy was compared with healthy, not with what people actually eat.

But keeping quiet about it would be dishonest. Between two equally varied diets, the plant-based one did better on some markers. Anyone telling you the type of diet doesn’t matter even a little is rounding something off, too.

So, more precisely: the first question isn’t plant versus animal. It’s varied versus monotonous — and that’s where a much bigger difference hides. Only once variety is sorted does it make sense to talk about the rest.

The one good question isn’t “what should I cut out of my diet.” It’s “how many different plants made it into my pot this week.”

Thirty plants a week

That’s where Spector’s practical recommendation comes from: thirty different plant species a week. It sounds like a task for an enthusiast with a spreadsheet. It isn’t — mostly because far more things count than most people think.

Legumes, grains, nuts, seeds, herbs and spices all count toward the thirty. A single curry base adds turmeric, caraway, coriander, fennel, mustard seed, ginger and garlic to your list — seven species before the first vegetable even hits the pot. Every variety counts separately: red lentils and beluga lentils are two items, not one.

And one more thing that needs saying fairly, because it tends to go unsaid: Tim Spector is a co-founder of ZOE, a company that sells personalized nutrition. The data from PREDICT and from the microbiome paper went through peer review and stand on their own — but there is a conflict of interest, and it should be stated.

That’s how we cook, too

This isn’t new information for us that we read and then rebuilt the kitchen around. It’s more that someone finally gave us the vocabulary for what we’ve been doing at Monáda from the start.

We’re not a vegan bistro, and we’re not a meat bistro. We refuse to fight that war, because by all accounts it’s built on the wrong question. On the daily menu, beef ragù sits right next to mung bean kitchari, and that isn’t indecision. It’s the whole point.

What we really pay attention to is variety in the pot. Moroccan harira has two kinds of legumes, four spices and fresh herbs. Ribollita is literally a recipe built on throwing in whatever is left over. Hŕstková (a “handful” soup of mixed legumes and grains) has variety right in its name. Vegetable sauté with sweet potatoes and black lentils or mung bean hummus with roasted root vegetables get past ten plant species on a single plate without anyone having to count.

This is also why we cook legumes so often, and why there are so many jars of spices standing in the kitchen. It isn’t a style. It’s the simplest lever available for the one number that, as far as we know so far, really works across tens of thousands of people.

And if you take one thing from this article seriously, let it not be a list of foods. Rather, that shift in the question — from “which diet should I choose” to “how many different plants did I have this week”. After decades, science has no answer to the first question. To the second, it does.

Let’s also say it plainly, so there’s no confusion: we’re not doctors or nutritionists, and nothing here is a treatment recommendation. If you’re dealing with a specific health problem, that belongs with a doctor, not with a pot. We just cook — and try to make decisions along the way that make sense outside the kitchen, too.

What you can cook from this

Seven dishes from our kitchen where that variety shows best. They’re not “healthy recipes” — they’re ordinary food that just happens to add up to a lot of plant species.