Updated 3rd November 2022

Will fermented foods improve my gut health?

Fermentation is a hot craze in fancy restaurants throughout the Western world. And fermented foods, like kombucha and kimchi, are even sold in corner stores. 

Listeners of this show will have heard that fermented foods might benefit our gut health. But these foods make us uneasy. The idea of letting food rot, then eating it goes against everything our parents taught us. So, is fermentation scary and dangerous? 

This episode will show you why it's not only safe but beneficial to eat fermented foods — and that fermenting foods is something you can try at home.

Jonathan speaks to Tim Spector and Sandor Katz — whom the food magazine CHOW calls a provocateur, trendsetter, and rabble-rouser — to better understand the fabulous world of fermentation.

  • Sandor Katz is a food activist widely credited with reintroducing fermentation to the United States and the United Kingdom. He calls himself a "fermentation revivalist."

  • Tim Spector is a co-founder at ZOE and one of the top 100 most-cited scientists in the world.

If you want to uncover the right foods for your body, head to joinZOE.com/podcast and get 10% off your personalized nutrition program.

Episode transcripts are available here. You can also follow ZOE on Instagram.

You can follow Sandor here. Find Sandor’s sauerkraut recipe here. And you can get his book here.

This podcast was produced by Fascinate Productions.

Transcript

[00:00:00] Jonathan Wolf: Welcome to ZOE Science and Nutrition, where world-leading scientists explain how their research can improve your health.

Fermentation is the hot craze in fancy restaurants across the Western world. Fermented foods with strange names like kombucha and kimchi are now sold in corner stores. Listeners of this show will have heard that fermented foods might benefit our gut health.

But these foods make us uneasy. The idea of letting food rot and then eating it goes against everything our parents taught us. So is fermentation scary and dangerous?

Many of us don't realize that some of our favorite foods are already fermented. Bread, cheese, wine. All amazing examples of how microbes can transform what we eat. This episode will show you why it's not only safe but beneficial to eat fermented foods, and that this is something you can do yourself at home.

In fact, we will even share an easy recipe to get started. Joining us on this episode is author and food activist Sandor Katz, who is widely credited with reintroducing fermentation to the US and the UK, with his book, Wild Fermentation. He calls himself a fermentation revivalist, and the food magazine CHOW calls him a provocateur, trendsetter, and rabble-rouser.

I'm also joined by Tim Spector, one of the world's Top 100 most cited scientists, and my co-founder here at ZOE to help us understand the science of fermentation and why it might bring unique health benefits. So abandon any fears you may have, and let's dive into the fabulous world of fermentation.

Sandor and Tim, thank you for joining me today. I'm really excited about this one. Five years ago, you know, when I started at ZOE, I really had no idea what fermentation was. To be honest, fermented food sounded like something I would have to throw in the trash. So I think our listeners are in for a treat to sort of hearing in an accelerated way from you about what this means.

And as always, what I'd like to do is start with a quick-fire round of questions from our listeners. So Sandor to start with. Do you think we should all eat fermented foods? 

[00:02:33] Sandor Katz: We already do. 

[00:02:35] Jonathan Wolf: That's a great one. Not quite a yes or a no, but that's fantastic. Is it hard to ferment food at home?

[00:02:41] Sandor Katz: No.

[00:02:42] Jonathan Wolf: And the last one, can you ferment fruit?

[00:02:46] Sandor Katz: There is nothing we could possibly eat that cannot be fermented. 

[00:02:51] Jonathan Wolf: What does it mean to you to be a fermentation revivalist? 

[00:02:55] Sandor Katz: Fermentation has been an integral part of how people in every part of the world make effective use of whatever food resources are available to them. It's part of our cultural legacy, everywhere. And yet over the past several generations, fewer and fewer people have been practicing fermentation. And so when I talk about myself as a fermentation revivalist, is really trying to, you know, revive interest in these, ancient practices and, basically help people feel confident to bring them into their home kitchens.

[00:03:33] Jonathan Wolf: All right, and I think we're gonna come back to a bit of that in more detail later. Tim, does fermented food have proven health benefits?

[00:03:40] Tim Spector: Yes, in some cases, but most fermented foods have not been tested fully.

[00:03:45] Jonathan Wolf: Is eating fermented foods better than swallowing probiotic pills?

[00:03:50] Tim Spector: In general? Yes. 

[00:03:52] Jonathan Wolf: And finally, can we consume too much-fermented food and drinks?

[00:03:57] Tim Spector: You can consume too much wine. That's true. But in general, if it's non-alcoholic, I don't think so. As long as there's variety.

[00:04:05] Jonathan Wolf: Fantastic. So I think we'll come back to many of those, but why don't we just start right at the beginning Sandor, I think the initial question is, isn't fermentation quite a niche?

Why would we even talk about this topic? 

[00:04:17] Sandor Katz: Well, I mean, every person in every part of the world eats and drinks products of fermentation almost every day. I'm not sure how you could call that a niche type of food. Think about the kind of diet that, you know, maybe people in the UK or people in the US have, you know, bread is fermented, cheese is fermented, cured meats are fermented. The condiments that we use are fermented. Olives are fermented. Pickles are fermented. Coffee is fermented. Certain kinds of tea are fermented. Chocolate is fermented. Vanilla is fermented. Obviously, beer and wine are fermented. I mean an incredible range of, you know, foods that are really everyday foods are products of fermentation.

[00:05:05] Jonathan Wolf: And so I think that probably opens up our minds to the reach fermentation. What is it and why is it something specific that we would think about and that you've really sort of dedicated, I guess, your life to?

[00:05:16] Sandor Katz: Well, broadly speaking, fermentation is the transformative action of microorganisms. For thousands of years, long before we specifically knew of the existence of microorganisms, people have been working with the reality that these organisms inhabit our food. And of course, one possibility is that microorganisms decompose our food into a disgusting, ugly mess that nobody would ever put into their mouths -

[00:05:44] Jonathan Wolf: - which I think is for many of us, like how we naturally think about these things, right? I think this is the world that many of us have been brought up with.

[00:05:53] Sandor Katz: I mean, many of us are victims of what I would call the war on bacteria and this sort of, the indoctrination that bacteria are our enemies. But for thousands of years, people have been working with these invisible life forces on our food. And you know, with our ancestors, powers of observation, and trial and error, people in every part of the world developed techniques for working with these organisms so that rather than decomposing our food, they somehow improve our food.

They produce alcohol, they make our food more stable for storage. They, make our food more delicious. They make our food more digestible. Fermentation is just an essential part of how people everywhere have been able to make effective use of whatever kinds of food resources are available to them. We all are familiar with the products of fermentation. But the thing that has disappeared from most people's lives is familiarity with the process of fermentation. And because it has largely disappeared into factories, we imagine that it must, you know, require sterile conditions, require a microscope or a knowledge of microbiology.

We project all of our anxiety about the idea of cultivating bacteria onto the process of fermentation, when in fact fermentation is a strategy for safety and people have been doing it with the simplest of facilities and you know, really without any knowledge of microbiology for thousands, literally thousands of years.

[00:07:36] Jonathan Wolf: And so historically, why did our ancestors ferment food? And you touched a little bit, but help to understand, you were sort of describing something that's very central. Why were they fermenting their food? 

[00:07:47] Sandor Katz: Well, for a variety of reasons. I mean, to produce alcohol, I mean, absolutely the production of alcohol is the most widespread application of fermentation.

It's the only way anyone has ever created alcohol, and every kind of carbohydrate source we know about has been turned into alcohol. Beyond alcohol, especially for people in temperate environments with limited growing seasons, preservation has been a very important application of fermentation. But you know, fermentation is practiced in, you know, tropical regions of the world just as much as it's practiced in temperate regions of the world.

And, you know, in tropical regions, it's less about the preservation of food to feed people through a long, harsh winter. And it's more about removing toxins from food, making things more digestible, making things more delicious. So, you know, there's a variety of practical benefits to fermentation, but there's always a practical benefit to fermentation.

[00:08:45] Jonathan Wolf: Got it. So you didn't start with taste. You started with a lot of practical reasons, whether that's to generate alcohol, which, and we know human beings, many of them are quite keen on alcohol. But also you're talking about preservation. Can you explain a bit more about what's going on in that second case? So, you know, I've got food, I'm generally worried about this food going off quite fast, which is part of why I think, you know, I was taught by my parents to be worried about it going bad and these microbes. How can these microbes that, you know, I tend to associate with food going rotten, how are they actually able to be in this world where you're saying, Hey, this is making it safer, and this is preserving food? 

[00:09:20] Sandor Katz: So, I mean, first of all, I should point out that there's a great deal of biodiversity on all of the plants and all of the animal products that make up our food. And so really the big question in fermentation is which organisms are going to grow?

And generally in the case where we're trying to preserve food, we are creating conditions that encourage the growth of certain organisms and simultaneously discourage the growth of other kinds of organisms. And we want to encourage the type of organisms when our objective is food preservation. We want to encourage the acid-producing organisms, so in most cases, that would be lactic acid bacteria.

And so once the lactic acid bacteria. Start acidifying the environment and the pH in that environment goes down, which has the effect of narrowing the range of what other organisms can survive. And it's very convenient for us that in a sufficiently acidic environment, the organisms that we associate with food poisoning and illness cannot survive.

You know, acidification of food through fermentation is just an incredibly effective strategy for food safety and you can't really have effective food preservation without having food safety at the same time. I think that, yeah, perhaps the most vivid example of this would be milk. And you know, for those of us who grew up in the 20th century, you know, we all had a refrigerator in our, I mean, not everywhere in the world, but I'm assuming most of the people listening to this podcast grew up with a refrigerator.

Fresh milk really has not been a possibility for most people throughout history. People with cows and goats could have fresh milk, but anyone else was drinking soured milk. In the English language, we have this word that's become obsolete—Clabbered milk.

Clabbered milk is simply milk, typically raw milk with its, you know, indigenous bacteria dominated by lactic acid bacteria intact when it just sits on the counter at ambient temperatures, those organisms consume lactose and produce lactic acid, and the milk acidifies. What most people throughout history have enjoyed in terms of dairy products has been fermented forms of dairy the fermentation makes the dairy more stable by acidifying it or in the case of cheese making, also by removing some of the watery aspects and making it something drier and denser.

[00:11:51] Jonathan Wolf: I'm sure Tim would be up for trying the sour milk or any other variant of this that you can provide. 

[00:11:59] Sandor Katz: Everyone listening to this is familiar with fermented milk and you know, yogurt would be an example of fermented milk. Kefir would be an example of fermented milk. And for these, we use specific starters, but we try to think of concepts about where they came from, they were spontaneous occurrences in some places that people developed a technique to perpetuate. 

[00:12:21] Jonathan Wolf: So I think it's really interesting that you know, we live with all of this, we tend not to think about them as fermented products normally, and that originally there's a sort of this self sterilization is sort of what you're describing, right?

That there's this sort of magic process that makes us healthy without what we're all used to of this idea that you've got to sterilize through, you know, heating something at a very high temperature or you know, spraying it with something. I guess many of the people listening to this podcast are particularly interested in about, how this might impact, in fact, health. So you're describing a world where really we were focused on being able to sustain these products, you know, have access to them afterward. Is the health products just, you know, are they real? Are they a byproduct of this? How do we understand this? 

[00:13:05] Sandor Katz: They're definitely real and it's not a new idea.

I mean, I think in many different cultural contexts, there has been, you know, the idea that particularly these live fermented foods, whether it's yogurt or kefir, whether it's sauerkraut or kimchi or pickle brine, but, you know, there's longstanding folklore recognizing some of the special nutritional qualities of these live ferments, and I think in our age of microbiology and PCR testing and more sophisticated techniques for understanding what's happening, there's been quite a bit of affirmation of the idea that these live fermented foods have special health benefits, not the least of which is probiotics, the bacteria that are in them that sort of continue to have a life and influence in our bodies. 

[00:14:03] Jonathan Wolf: And Tim, I'd love to get your thoughts. So I know a lot of your research is around exactly these areas. 

[00:14:08] Tim Spector: Yes. Well, as Sandor said, Chinese medicine and Indian medicine often had fermented foods at their base, so they understood. They didn't exactly know why, but they knew they had some benefits. And I think what people need to understand is that when I talk about fermented foods, it's not things like supermarket bread or the process involved in it, but it's still got live microbes at the end.

And I think we don't really have a word for that yet, but it's sort of live fermented food, I guess, might be the way to describe it. Often has very much more in the way of microbes and microbe diversity than buying your probiotics at the health food shop. Because generally in a health food store, you're gonna get one, maybe three varieties of microbe that you hope are there and hope aren't dead.

Whereas if you have standard kefir or kimchi or kombucha, you can have at least 10 varieties, sometimes up to 30 varieties of live microbes. All different in different varieties of those products and in large numbers. And when populations, like the Koreans who I looked up recently, actually eat 36 kilograms, each, of kimchi.

[00:15:27] Jonathan Wolf: 36 kilos . That's a lot of kimchi. 

[00:15:29] Tim Spector: That's a lot of kimchi, but they start young and you know, they happen to be the healthiest Westernized population. And that's probably no surprise that that happens. But in a way, what they're doing is every day they are having this extra probiotic supplement of an extra 20 species that they're ingesting, including yeasts, fungi, and other things that aren't traditionally in health food stores.

So I think that's important. 

Well, I'm just admiring Sandor's kimchi on the board. 

[00:16:01] Jonathan Wolf: For everybody else who's listening to this Sandor has just picked up this spectacular jar. Sandor, what is in that jar?

[00:16:08] Sandor Katz: Kimchi that I just made the other day. It's some cabbage, cabbage, and spices, basically. The spices are rice-based paste with, a little bit of fish sauce in it, but in the warm summer temperatures, it's fermenting very vigorously and it'll have to go into the refrigerator soon.

[00:16:27] Jonathan Wolf: How hard is it to do that? Could you talk us through what it would take if someone was listening here and would like to make their own kimchi at home? 

[00:16:34] Sandor Katz: Sure. Well, let me, first of all, say that the easiest way to ferment vegetables of all is what I would describe as the sauerkraut method, and dry salting the vegetables.

All you do is shred vegetables, create a surface area, and lightly salt them. There's no magic number about how much salt. You salt it lightly. Mix it up. Taste it. Add more salt, if desired. Add seasonings if you like. Caraway seeds or garlic or chili peppers or anything. Squeeze the vegetables for a few minutes and that helps get them juicy.

Once they're juicy and you like the balance of flavors, pack them into a vessel so they are submerged under their own juices. And then, wait some days or some weeks, and that's the whole process. For making kimchi, there's an additional step to the process, and that is that I shred the vegetables and I submerge them under a saltwater brine solution.

I don't measure the salt, but I taste it and I'm going for the flavor of the sea. I want it to be somewhere around 5% or 6% salt. 

[00:17:39] Jonathan Wolf: Pretty salty. 

[00:17:40] Sandor Katz: Pretty salty. And then you just leave that for 24 hours, and then the next day you go ahead and you make a little spice paste. 

[00:17:48] Tim Spector: You ever add a little spoon of sugar sometimes to the kimchi?

[00:17:52] Sandor Katz: No, I mean, basically the rice paste does the same thing. So typically people add some sort of more concentrated carbohydrate, and that could be grain-based, like my rice paste. It could be fruit based. Sometimes people will use pears or apples or other fruit. Sometimes people just add a spoon full of sugar or honey.

There are various ways to achieve that, but just adding some more concentrated carbohydrate elements just makes for a more vigorous, faster fermentation. It doesn't keep it sweet. 

[00:18:26] Tim Spector: And just to say that there are infinite varieties of kimchi and if -

[00:18:28] Sandor Katz: - Absolutely -

[00:18:29] Tim Spector: -you go to Korea, each family has their own version, don't they?

So it's, you know, there are infinite numbers of potential microbes that, you can get out of kimchi. And that's what the publications show. I think there's, you know, over a hundred different types of microbe you can get from a similar mix of kimchi. But what I think is interesting is also for people who aren't aware of the difference between say, the health benefits of kimchi versus say, kefir is that -

[00:18:59] Jonathan Wolf: And Tim, I think there'll be plenty of people listening to this who won't even know what kefir is, so just help us to understand.

[00:19:05] Tim Spector: Kefir in the States. Kefir is fermented milk. So this is what Sandor was talking about. You have these grains, which you just put into normal milk and then leave for a few days and they start to produce this Kefir which is all around the world and the versions in India and all, all over the place.

It's just like a super yogurt, I would call it. But the difference with kimchi is that it's got, you eating vegetables, which have fiber. And as you eat them, they're giving off the probiotics, which are these microbes, but the actual hard texture of the original vegetables, 10 or so different plants you've got in there.

Also, helps your gut and keeps those microbes going. So it's sort of you're getting the prebiotic, and the probiotic. The fertilizer and the seeds are both at the same time. And I think that's what's unique about those sorts of types of fermented vegetables that we don't often talk about. And that's probably why they potentially have greater health benefits than just the pure microbes on their own.

I don't know if Sandor would agree.

[00:20:16] Jonathan Wolf: And Tim, I think people are listening to Sandor's description and say, That sounds delicious, right? Sounds amazing. You know, so you definitely think about something you want to eat. Can you help us understand a bit more, you describe the fact there are lots of microbes, but can you help to sort of fill in the details?

So why is it that eating this thing, which is fermented is actually improving our health? And also particularly, there are two parts of this, and I just want you to sort of unpack a bit for the audience because the food itself is changing, isn't it? And you've got these microbes. Could you just explain a bit more like why both of those things are affecting our health?

[00:20:51] Tim Spector: Yeah, so the food itself, we know that if you're eating plants that have either a high fiber content or a high polyphenol content, which is the defense chemicals in plants that our gut microbes feed off, they are stimulating your community of gut microbes to help your immune system to help all aspects of your metabolism and infinite things we still don't understand.

So it's really important that the plants you're eating in something like kimchi are part of trying to get this big variety of plants in your diet. And I would say aim for your 30 plants a week. I'm sure Sandor does many more, but you know, just by having kimchi, you are getting probably about 8 or so of them, 8 or 10 different plants in one spoonful.

So that's important. They're feeding the whole gut community. And then you've got on top of that, you've got these microbes that are sitting on those foods that go through your intestinal system, and a lot of them get killed off, but enough get through the stomach acid to get to your lower gut where they will have an interactive effect on your microbes stimulating to produce good chemicals that are, again, really key for your immune system and your digestion, your metabolism, etcetera. So it's that double system of both feeding the original contents of your gut microbes, stimulating new ones to grow more of the good guys, and these probiotic microbes that don't live in humans.

Just passing through, has a beneficial effect. A bit like you know, rich, American cruise ships going through some poor island community, dispensing money as they go. So I think that's the analogy.

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[00:22:42] Jonathan Wolf: And so, Tim, just to make sure we're clear on that, what you're saying is when I'm eating something that might have some live bacteria in it, whether it's yogurt or your kimchi, the microbes aren't necessarily staying in my gut permanently, which is I think what most people were assuming you are saying, probably they're passing through and yet they can still have this positive effect.

[00:23:02] Tim Spector: That's correct. Exactly. So we used to think that they did well, there were the naysayers about 10 years ago, who said, well, none of this works because they're either killed off at the stomach or they can't stay in the human gut. And now many science experiments have shown that's only partly true and they still have a beneficial impact.

But it sort of means you have to have them regularly to be healthy. I think that's the point. You can't just have a once-a-month fermented food fest and hope that it's gonna last you for the whole month. You have to have these things regularly, and when you do, then they are healthy, and the data supports them.

[00:23:37] Jonathan Wolf: So it's a bit more like taking medicine. It has its impact, but you know, it passes through and it falls away. And so I need to keep doing this.

[00:23:45] Tim Spector: It's not every day, but it's, yeah, every few days. 

[00:23:49] Sandor Katz: But it's also like food because, you know, we can't just eat once a month and have all of our needs met. I mean, it's not like medicine.

It's like food where, you know, we need to eat them regularly. I only react to that because people sometimes imagine they're like medicine and you know, they say, oh, what's the correct dosage of kimchi? And it, I mean, it's not medicine like that, it's food, but you know, it's food which can support our health. A lot of different kinds of foods really are like that.

[00:24:19] Jonathan Wolf: And Sandor, one of the things I find amazing, and again, I think this shows you how I guess medicalized I am, is that you didn't say, you go and add the particular correct bacteria into your kimchi, right? In fact, you didn't even mention anything about the bacteria, they just sort of magically appeared.

Could you help us to understand, and why don't we have to be really careful about this step?

[00:24:46] Sandor Katz: Sure. The reason why we don't have to add some specific pure culture starter that's been propagated in a laboratory is that you know, we have a clear understanding that all plants are host to lactic acid bacteria. I mean, there's a broad consensus among microbiologists and botanists that all plants growing out of the soil on planet earth are host to lactic acid bacteria.

And so if we create the conditions in which the lactic acid bacteria can thrive. They are always there to do so. Now, I mean, you could certainly find on the internet a packet of the white powder of lactobacillus Plantarum, which people will be happy to sell you as a starter for making sauerkraut or kimchi or other kinds of fermented vegetables. But, you know, I would consider that to be an exploitative product because the lactic acid bacteria are already present in vegetables and you don't need to add a starter. 

[00:25:50] Jonathan Wolf: That's amazing. So you are saying because I thought maybe it was in the air, you're saying actually the plants themselves, it's not like they come pretty packaged with their own bacteria.

You literally just have to add the salt, put them in the jar, and you're away. 

[00:26:03] Sandor Katz: I mean, they're growing out of the soil, and the soil is this just incredibly complex system that we're only beginning to develop tools to be able to appreciate the level of complexity of it. But the seedling is emerging. Partly with the help of microorganisms in soil, the plant is able to grow and flourish with the assistance of microorganisms in the soil.

And so, you know, the soil is the source of all of this. And the organisms that enable the animals that we raise for our food that are grazing on plants, you know, it's the soil organisms that are feeding their gut bacteria as well. So, I mean, I would say the microbial system really begins and ends in the soil, and that's the source of the constant renewal of life really.

[00:26:57] Jonathan Wolf: There's a sort of beautiful connectivity as you talk about this, right? Where actually, you know, through the food and the bacteria, you are connected back to the soil and the world, and that's obviously very different from the interaction with food that most of us have now in the West, where everything comes in a, you know, packaged, plastic wrapped solution.

And you know, the more that it has been separated and sterilized, the better. And I do think that it's amazing that just as we've been discovering how important these microbes are inside our guts for our health, we also see equally well that we always used to have this very interactive back-and-forth connection with the bacteria outside us.

And I guess, you know, what I'm hearing is that fermentation is one of these ways that you can start to maybe pull this back together again. 

[00:27:51] Sandor Katz: Absolutely, and I mean, I think beyond fermentation, I mean we really have an imperative to reconnect to the sources of our food and reclaim our food. You know, food is not a commodity like every other commodity.

I mean, you know, food is what enables us to continue to exist. Food comes from plants and animals. The pursuit of food connects every kind of organism in the world with its environment and, you know, human beings in the name of our sort of supposed progress have really sort of severed that connection. And, you know, I think we need to become reconnected to the sources of our food and reclaim our food as a product of our environment that, you know, we interact with.

[00:28:41] Tim Spector: Absolutely agree with everything Sandor's been saying. And I only started fermenting about 10 years ago, but I found that having a jar, whether it's kimchi or kombucha, which is fermented tea, you can actually see the process that's not only going on inside our guts and our bodies every day, but also gives you an idea of what's happening in the soil and plants in a visual way.

And I think this is why everybody should be teaching their kids to ferment something to really understand not only our relationship with food, but you know how we all have these similar pathways as organisms. And I think it's incredibly insightful as we see the whole thing unifying together and realize that what's happening in the soil is very similar to what's happening inside our own bodies, and is not nearly as different as we expected.

[00:29:35] Jonathan Wolf: So I think there'll be lots of people listening to this who are really excited about the idea of fermenting but also feeling really daunted. And you've already mentioned kimchi and kombucha, and there are a lot of scary words that maybe they don't really know anything about. Let's say that they're saying, I would like to start but I'm completely new to this.

What are the best-fermented foods to get started with? And particularly maybe for people who think they don't like fermented food, you know? And I think I historically was definitely in that category. I grew up thinking all those strong flavors and acidic flavors were disgusting, you know, fermentation, that sounds sort of gross. And as you said, Sandor, I did that while happily, you know, eating a double-cheese pizza. So, you know, I didn't know what I was talking about, but I think that's where they come from. Is the entry point, does it have to be, you've got to figure out kimchi? What would you advise? 

[00:30:26] Sandor Katz: No, no. Not, not at all.

I mean, as I said earlier, I mean, I think that the sauerkraut method is just the simplest way to ferment. I mean, you shred vegetables, salt them, season them, pound them, or squeeze them for a few minutes to get them juicy and pack them into a jar. But there's an incredible range. So I mean, on my counter right now, here, this is something I made yesterday. These are, I call these dilly beans. And they're basically immature beans, green beans, as some of these are red, They're different varieties.

[00:30:56] Jonathan Wolf: Yeah. They look like they're about three inches long, I would say. Or I guess, What's that? 10 centimeters in what is that? Like, uh, half a litter jar, something like that?

[00:31:08] Sandor Katz: Yeah, it's a litter-size jar, but it's just these green beans, garlic dill, and a saltwater brine solution, and I'll probably ferment them for four or five days. I already tasted one this morning. One day old. I want them to have a more assertive sourness, so I'm giving them more time. But that's a very simple way to do it. You know, fermented cucumbers were really my gateway into fermentation.

[00:31:35] Jonathan Wolf: They were the gateway drug, where they Sandor? 

[00:31:38] Sandor Katz: Yeah, so you can do it with cucumbers, but cucumbers end up being kind of the most challenging vegetables to ferment only because they get soft and mushy. So in my book, Wild Fermentation, you can find some very specific suggestions about how to ferment cucumbers and keep them crisp.

I have another jar here. This is a Chinese style called Pau Tsai and it's basically vegetables in a perpetual brine I've been maintaining this brine for more than two years now and I mean the flavor just gets better and better.

[00:32:13] Jonathan Wolf: So you are sort of constantly topping it up and emptying it, Sandor, almost like a sort of making bread where you're always keeping a bit for the next one? Is that how this works? 

[00:32:22] Sandor Katz: Well, no. What I'm doing is I'm removing the vegetables that are mature pickles and eating them, and then putting fresh vegetables in them. And then over time, because salt and the flavor of the seasonings migrate out with the mature vegetables, then I'll add not only more vegetables but a little bit more salt, a little bit more of the Sichuan peppercorns, a little bit more of the ginger and the other seasonings.

So really what I'm trying to say is that there's a wide variety of different traditions for fermenting vegetables, and I even meet people who are creating new traditions. I mean, you know, there are not like a finite number of ways of doing this. You know, the concepts are very, very simple and I try to explain them as clearly as I can in my books.

But then you can experiment with different seasonings and different kinds of vegetables. You can make beverages that are infusions of fermented vegetables. You can make a mix of 20 different vegetables. You can make just any single kind of vegetable fermented alone, I love the Southeast European style of fermenting, whole heads of cabbages, and then you peel off the outer leaves of the cabbages and then you can wrap things in them and make, you know, beautiful stuffed cabbage things in it.

So really what I'm saying is that there's not a, you know, very small finite, number of possibilities. There are a lot of different possibilities. And in my kitchen, you know, I'm definitely eating fermented vegetables with pretty much every meal, but not necessarily the same one. So I have a lot of, you know, variation in my palate with different seasonings, different levels of sourness.

[00:34:04] Jonathan Wolf: I'm definitely feeling hungry now, and we will make sure in the show notes we have links both for the very simple sauerkraut recipe and of course through to Sandor's book, for those who really want to fully experiment. I think some people will be listening to this and saying, this sounds great. I'm not ready to try and experiment at the home and do all of this myself.

Is it possible to eat fermented foods through things that you can purchase at the store? 

[00:34:30] Sandor Katz: Oh yeah, absolutely. I mean, I know you have listeners from all over. I was just in the UK a few weeks ago. My first trip teaching in the UK was in 2008, and I remember trying to find live fermented vegetables in stores there, 15 years ago, and I just, I couldn't find any. 

Now when I go, they're really quite widely available. So, you know, generally a live fermented vegetable, you're gonna find in a refrigerated section if they're, you know, if they're on a shelf without refrigeration, typically that means they've been heat processed before going to the store.

So you really want those live bacteria. So if you're shopping for them, you want something in a refrigerated section. And generally, it is going to advertise the fact that it is raw live unpasteurized on the label. But that's really what you want. 

[00:35:20] Tim Spector: There's been an explosion in the UK of things like kefirs and kombuchas that you can buy in stores, and there's a suspicion that many of them do not contain live microbes.

They're easily using really ultra-fine filtration systems that get rid of some of these microbes or that in order to do big quantities and ship 'em around the country, they have to basically pasteurize it. Or the sugar content is so high that it might inhibit the microbes. Or occasionally you've got things like apple cider vinegar that have such high acidification, it kills off the actual microbes in there. The mother, etcetera, is actually dead. So it's great to have these products, but I feel they could be exploited. And I wonder if you had any thoughts. 

[00:36:12] Sandor Katz: Sure. I mean, I think that that's a really important question. Definitely the more educated you can make yourself as a consumer, the better quality products you can find.

Generally, I would advise people to sort of steer away from big national brands and support, you know, smaller regional brands because they have less reason to, you know, sort of try to, you know, develop these workarounds. So yeah, I mean, I would say, you know, buy as local of a product as you can and if you have any questions then you know, really try to pose those questions to the producers and, you know, see if they can answer them to your satisfaction.

[00:36:54] Tim Spector: Do you think too much sugar is a problem for the health benefits of some of these? In order to increase the number of people, you know, trying them, they're making them sweeter and easier to test. Do you think there's a danger that that really does inhibit the microbes? Have you tried any of that, sort of your stuff yourself?

[00:37:12] Sandor Katz: I've experimented with everything, but you know, there's a reason why I mostly talk about fermenting vegetables and don't talk as much about, you know, lightly fermented soft drinks that are based on sugar. And because I myself prefer not to consume a lot of sugar, Not really for reasons of the microbiome, but just for, you know, general health.

And I think that you know, part of the appeal of some of these lightly fermented soft drinks has been people who already have sort of like a sugar habit transferring it from one type of beverage to satisfy that to a different type of beverage that they perceive to be healthier. And, you know, I think it's true that you know, drinking lightly fermented sweet beverages probably is better for you than drinking Coca-Cola.

But if you're ingesting, you know, in the end, the same amount of sugar, you still have certain health challenges as a result of that sugar. So I would say, you know, in anything sugar-sweetened you, you know, you really want to exercise restraint and moderation, and those are important values. And you know, just to get back to a question that Jonathan asked Tim earlier, can you eat too many fermented foods? I mean, I would say in the realm of the vegetable ferments that I'm talking about, salt would be the limiting factor.

And so especially a lot of traditions where, you know, these foods had to do with survival through a long, harsh winter. Sometimes people made them with extremely high levels of salt. And in general, I advocate for people to use more moderate levels of salt because for most people, learning how to make it today, they're not looking for survival through a long, harsh winter. And instead, they're looking for, you know, the probiotics or something that's gonna taste delicious and maybe, you know, encourage their family's good health. But you can make these things with really exceedingly small amounts of salt. But I would think that in general, the limiting factor as to how much a person should eat would be the level of salt in it.

And, you know, we all need some salt, but too much salt creates, a whole set of problems. 

[00:39:16] Jonathan Wolf: That's a really interesting way to think about it. So basically there's only so much salt you should take and that's really the limit on your fermentation. There's no other way to be limited.

So I know we're coming towards the end of the time. I would love, Sandor, maybe to wrap up with five tips for trying fermentation yourself. I think there'll be lots of people who've listened to this who are saying, You know what? I'd really like to try it this weekend. And by the way, it's great, for those of you with kids, like it's an amazing thing also to do with children or to do with as sort of family activity.

What would be your 5 tips for someone who's coming into this fresh?

[00:39:48] Sandor Katz: Okay. Number one, do not be afraid. Do not project all of the anxiety you've ever had about bacteria onto the process of fermentation. Understand that these are ancient practices that have been tested over time and that they are extremely safe.

Okay, number two. Fermentation is all about manipulating environmental conditions so as to encourage the growth of certain organisms and simultaneously discourage the growth of others. Understand what the conditions you're trying to create are. In the case of fermenting vegetables, it's simply getting the vegetables submerged, which protects them from the flow of air with oxygen, and that's what supports the flourishing of the lactic acid bacteria rather than say, spores of molds.

So, you know, understand the condition you're trying to create. A third, what I'll say that's a little bit different is, you know, don't overthink it. Don't try to imagine everything that could theoretically go wrong and make yourself crazy. You know, these are simple processes, like accept the simplicity of them.

Number four, don't be afraid to experiment. It's the process that's important. You know, if you add a different kind of vegetable or a different kind of seasoning, that's great. As Tim was saying about kimchi, kimchi is not one thing. You know, kimchi is the name for this, you know, incredibly diverse tradition, and there's a lot of regional variation, but there's also just family recipes and you know, every grandma who has her own secret, something that she adds into it.

So don't be afraid to experiment. Don't be afraid to play. Number five, be creative about how you incorporate these foods into your diet. I think for a lot of people who aren't accustomed to them, that's the hard part. And just experiment. Like, I love it with eggs. I love it as a condiment on a sandwich. You know, there are endless applications.

I love to use the extra juice of the sauerkraut or the pickles in salad dressings, but, you know, be creative. 

[00:42:00] Jonathan Wolf: That's fantastic. And I would add, I asked Sandor this question, when we chatted last time, and he had five, almost completely different tips. So I feel that we can ask this again and we get another five brilliant ideas.

So next time I'm gonna ask this again and slowly we're gonna build this up to this magnificent list.

[00:42:17] Tim Spector: I'm a big fan of smelly raw milk cheese with kimchi is one of my favorite accompaniments. So then you've got the microbes that everyone's been eating for centuries. Is happy, with these other new sets of microbes. And so you've got a very gut-friendly dish there. 

[00:42:35] Jonathan Wolf: So I think I could now go and ask for 10 more recipes and everyone will just listen and salivate, but I'm afraid we're at time. So I'd just like to do a quick summary as we always do. So firstly, we discover that fermentation is actually something that we've been doing for thousands of years. It's completely normal. It's not this sort of weird new thing that lots of foods are fermented and in fact, Sandor gave us a list, which had almost every food we think about, many of which we might not think of as fermented. You can definitely do this at home, and in fact, you don't need to do anything really complicated because the plants you want to ferment carry their own bacteria.

We then discussed the health benefits. Then I think we had a big watch out from Sandor about sugar drinks pretending to be healthy because they're likely fermented. And just in general, needing to be careful if we're going to be buying these fermented products from shops. And then finally, we had five tips for trying this yourself.

Don't be afraid. Understand the conditions you're trying to make. Don't overthink it, it's not rocket science, and it's gonna be okay. Don't be afraid to experiment because actually these things like kimchi, it's not one recipe you have to do perfectly. It's sort of like a whole tradition and way of approaching.

And finally, be creative in how you add these fermented foods to your diet. You can add them in many more ways than you might think, so find the ways that work for you. I would add that we will definitely give the recipe for the dry sauerkraut method and would recommend that you all have a go. We will point you to some videos as well that show that this is really easy.

Just before we go, we've got a listener question from Sal that I'd like to ask Sandor and try and get him to answer. And his question was, Sandor, what's the most unusual food that you have fermented? 

[00:44:23] Sandor Katz: I mean, that's a hard question only because I just take it as a given that anything we could possibly eat can be fermented.

I would say that, in my travels, maybe the most unexpected fermented food that I tried, was in Colombia, in South America, and it was an amazon ferment called Tucupi, and it was basically the toxic cyanide-rich juice of cassava, fermented, which breaks down the cyanide compounds into benign forms, and then cooked down into this like tarry sticky, thick substance that was so incredibly delicious as a condiment.

So that was an unexpected one that I was served. 

[00:45:11] Jonathan Wolf: I love that. And one, you definitely want to make sure that the chef knows how they're making it sounds. Thank you, Sandor. Thank you, Tim, and I hope we can come back and talk about some more of these things in the future. 

[00:45:21] Sandor Katz: Great. Thank you so much.

[00:45:24] Jonathan Wolf: Thank you to Sandor and Tim for joining me on ZOE Science and Nutrition today. We hope you enjoy today's episode. If you did, please be sure to subscribe and do leave us a review, we do read all of them. If this episode left you with questions, please send them in on Instagram or Facebook, and we'll try to answer them in future episodes.

At ZOE, we want to improve the health of millions by understanding the right food for each of us to improve our health and manage our weight. Each member starts with an at-home test, comparing them with participants in the world's largest nutrition science study. If you're interested in learning more about ZOE, including how you can improve your own gut health through fermented foods, you can head to joinZOE.com/podcast and get 10% off your personalized nutrition program.

As always, I'm your host, Jonathan Wolf. ZOE Science and Nutrition are produced by Fascinate Productions with support from Sharon Feder, Dr. Yella Hewings-Martin, and Alex Jones here at ZOE. See you next time.

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