Fermentation happens when microbes (bacteria, yeast or mold) break down the carbohydrates in food and turn them into something else. Think of yogurt (bacteria convert the sugar in milk into lactic acid), or bread (a loaf will only rise once yeast has fermented the sugar in dough into carbon dioxide). A non-wellness-pilled normie will have some questions here. Is kimchi more elite than kefir? Should you be downing forkfuls of sauerkraut every morning or at night?
The internet, naturally, has many answers. We’re living through a gut health boom right now, so odds are pretty high you’ve seen your local influencer waxing poetic about their tangy jars of pickles and cabbage and carrots. Fermented foods have gold status in the wellness world—touted by influencers like Andrew Huberman—because they’re often teeming with gut-boosting prebiotics, probiotics and postbiotics.
To understand how to best integrate fermented foods into our diet, we spoke with Dr. Johnny Drain, a PhD-educated cook who recently published something of a bible on the subject, Adventures in Fermentation. “Human beings have been fermenting for as long as we’ve been human beings,” he says. “And the most surprising thing, that lots of people don’t realize, is that many of their favorite foods in the world have been fermented. It’s not just kimchi, it’s not just sauerkraut—which people might like or dislike—but bread, butter, any booze you drink, cheese, soy sauce, vinegar. Even coffee and chocolate.” Drain has been called a “microbial poet” by René Redzepi, the founder of the shuttered world-renowned gourmet restaurant Noma—so we’ll take his word for it.
GQ: Why did our ancestors originally start fermenting—without the benefit of seeing preserve jars all over their TikTok feed?
Dr. Johnny Drain: They were trying to get through winter. It’s a preservation technique. So it can extend the shelf life of stuff in the same way as salting or smoking or drying. But the other really important thing it does is break down macronutrients into forms that are more digestible for humans. So if you take the example of a soybean, our digestive systems are not that well set up to get every ounce of nutrition out of a soybean. If you let the microbes break it down first, then when you eat your soy sauce or your miso paste, it’s already broken down, so humans can extract more nutrients.
Is there a reason why fermented food and drink—chocolate, cheese, coffee, wine—are some of the best-tasting things out there?
The genius of fermentation is that it creates this kaleidoscope of flavors from very simple ingredients. If you think of sake, it’s made from rice and some funky molds. And the flavor profiles of sake are insane, it can taste like kiwi fruit, or like melon. It’s all the action of these microbes.
Which fermented foods are considered the best for your gut health?
The world—and science—is messy. So we’re not necessarily at that point yet where we can say, ‘Eat this, it will do this.’ There’s two defensible things you can say about fermented foods. One is that if you eat a diverse range of them in your diet, that’s associated with all sorts of positive health outcomes, and things like a reduction in inflammation markers. So the key piece of advice is not ‘You have to eat kefir,’ or ‘You have to make your own sourdough’ —just eat a bunch of fermented foods. Chocolate counts, coffee counts.
And then the other really key piece of advice is to eat more fiber. The microbes in your gut need to eat stuff to be happy. If you feed them what they like, they are more happy and diverse and multiple. The stuff they love is basically fiber, prebiotic fiber.
So, at the moment, we can’t say that certain fermented foods can fix specific gut conditions?
We lack this kind of one-to-one mapping: this fermented food to this ailment. That’s because of complexity on both sides. My microbiome is really different to yours. Even if we’re both healthy, we might have different microbes, different strains performing the same function. And then if you compare our microbiomes to someone, let’s say, who’s got Irritable Bowel Syndrome, they might lack the function that our guts have, but it might be because they lack or they have too much of a different type of microbe. And then on the fermented side, if you take two types of sauerkraut, they might have some of the same microbes, the same lactic acid bacteria, but they might have different strains.
Is there a “best” time of day to eat your fermented foods?
It’s very difficult to say, unfortunately. But what we do know is that the microbes in your gut change throughout the day. So at midnight versus midday, the populations, the sizes of the different communities of microbes in your gut will be different. They wax and wane over the course of a day, a week, a month. If you start living with someone, or even if you start sitting next to someone different at work, your microbiome will probably change because of your proximity to that person. People with pets have more diverse microbiomes because their pets are going out, messing around, and bringing things back. So if you can’t stomach a tablespoon of sauerkraut at 9 a.m., but you can at 5 p.m., save it for 5 p.m..
Is it true that fixing your gut can improve your mental health?
That’s real science. So you have this gut-brain axis, and you have neurons, kind of brain cells in your gut, and they are in constant communication with your brain. And so sometimes something like, ‘I’m hungry,’ probably is an interface between your microbes and the things they produce, these chemical compounds, triggering these neurons in your gut, that zip up to your brain, and then I become aware, ‘I’m hungry.’
If the goal is diversity in your gut, is eating one fermented food—like sauerkraut—less effective if you’re eating it every single day?
If you love starting your day with a spoonful of sauerkraut, don’t stop doing that. But, you know, every other day, drink some kefir, have some kombucha, have some coffee, have some cheese. My philosophy here is it should always be additive rather than reductive, because when it’s reductive, you get into these faddish diets, and you basically make people miserable because you’re trying to tell them they can’t eat this or that.
Stomach problems definitely seem to be trending on social media. Are we all coming down with more gut issues, or are we just getting better at identifying the symptoms?
I think a bit of both. Predominantly, it’s the awareness that your microbiome can be linked with mental health, your microbiome can be linked with your risk of heart disease, all sorts of different diseases. And these diseases that are dominating developed society now, like diabetes and obesity. But do we have more of them? Certainly. It’s kind of circular. All of this chat around ultra-processed foods and how many of us now in the developed world are going to be diabetic or obese—something has gone wrong with what we’re eating and how much exercise we get, the lives we live, that is impacting the gut and the microbiome as well, which can also lead to some of these diseases.
Dr Johnny Drain is the author of Adventures in Fermentation, available here.
This story originally appeared in British GQ.
