Fermented vegetables are high on the list of things I’ve received the most questions about from readers of Darwinian-Medicine.com. That’s not particularly surprising, seeing as I have talked a lot about fermented vegetables in relation to gut health and microbiome restoration here on the site; was in charge of planning and conducting the first ever clinical research study on fermented vegetables and irritable bowel syndrome; and have written and published an eBook on fermented vegetables and gut health
One of the things that a lot of people wonder about is how often (if at all) they should consume fermented vegetables, as well as how much they should eat at each sitting. I’ve talked about those issues here on the site in the past, and I also devoted a couple of pages to them in the eBook. There are several reasons why I now choose revisit them. The first reason is that I suspect that a lot of people are still unsure about what constitutes the best strategy in this arena. The second reason is that my position on this matter differs from that of most other health and fitness writers. The third reason is that I strongly suspect that a lot of people are taking in excessive amounts of fermented foods, and as a result end up undermining, rather than enhancing, their health.
With that said, let’s jump in with my answer to the question posed in the title…
Over the years, my perspective on fermented foods and gut health has changed quite a bit. When I first started getting interested in fermentation as it relates to gut healing & health many years ago, I was led to believe from reading about kefir, kimchi, sauerkraut, and the like online that one ideally should consume some type of fermented food every day, preferably at every meal. For some time, that’s what I ended up doing.
However, over time, I started to suspect that this practise was destabilizing, rather than empowering, my microbiota. I began thinking about the issue at hand from an evolutionary and biological point of view, which made me realise that much of what I’d read about fermented foods online had little to no scientific rationale behind it. This eventually led me to change my stance on certain matters related to fermented foods. For many years now, I’ve advocated a more cautious approach to fermented foods.
The dark side of fermented foods
The first thing that’s important to recognize is that fermented foods are a novel part of the human diet. Wine, cheese, and many other fermented food products have been around for many thousands of years; however, they weren’t a part of the preagricultural nutritional environment that contributed to molding the human genome over millions of years. Our ancient ancestors may have occasionally consumed some foods that had started to ferment as a result of microbial growth; however, they didn’t produce large quantities of fermented foods. They ate mostly fresh food. This is important to recognize, as it implies that we may be inadequately adapted to consuming a lot of fermented foods.
Fermented foods such as kimchi and kefir are loaded with bacteria. That’s usually considered to be a good thing. What’s often overlooked is the fact that all organisms are a part of the battle for existence that exists in nature. If one infuses a lot of new organisms into an ecosystem, those new organisms won’t simply get into line and start peacefully cooperating with the organisms that are already present in the ecosystem. Rather, they will fight for their survival. Microbes are no different from other organisms in this respect. Actually, in many ways, they are even fiercer. Lactic acid bacteria for example, which are abundantly present in fermented foods such as sauerkraut, produce compounds (e.g., bacteriocins) that are toxic to certain other types of bacteria. Moreover, it’s important to recognize that fermented foods such as sauerkraut are high in lactic acid and histamines, which some people, in particular sick individuals, may not tolerate that well.
Over the years, it has become increasingly clear to me that it’s unhealthy to consume large quantities of fermented foods such as sauerkraut and kefir on a daily basis, in part because it will destabilize the gut microbiota. The quantity/dose that one can safely tolerate depends largely on the stability and functionality of one’s gut microbiota. If you harbor a stable, diverse gut microbiota, you can probably consume more fermented foods without experiencing any major adverse effects than if you harbor a dysbiotic, degraded microbiota.
My approach to gut healing & health
My approach to gut healing & health differs from the one I’ve seen outlined on many health blogs. Some places I’ve read that everyone, irrespective of health status, could benefit from using probiotic supplements and taking in a lot of fermented foods. I take issue with this assertion. As I see it, people who harbor a healthy gut microbiota don’t really need to consume fermented foods or take probiotics. The most important thing is that they feed the friendly microbes that are already present in their intestines. It’s also good if they expose themselves to new types of bacteria, for example by consuming fresh, raw vegetables; however, they certainly shouldn’t overwhelm their guts with bugs by using a high-potency probiotic or daily filling their dinner plate with plenty of sauerkraut.
In my work with clients, I primarily use fermented foods as a tool for microbiome repair. If a person approaches me because his gut microbiota is in a sorry state, I will, with a high degree of certainty, tell him to incorporate fermented vegetables into his diet. However, I will be sure to point out that the goal is to gradually introduce a diversity of friendly organisms into the gut and building a healthy microbiota; not to bombard the gut with probiotics. I may also tell him that he most likely won’t have to consume fermented foods indefinitely. If he manages to fix his microbiota and recover his health, he doesn’t have to focus so much on diversifying his microbiome any longer. If that’s the situation, he may be best off following in the footsteps of our Paleolithic ancestors, who ate primarily fresh food.
This is not to say that I would strongly advice healthy people to never eat any type of fermented food. If one select high-quality products and only consumes small quantities, any potential adverse effects will be small. It may even be that one attains some health benefits; however, this is something that each person will have to judge for himself. Whereas some people may find that they do okay on a diet that includes small quantities of fermented foods such as sauerkraut and kimchi, others will likely find that they are better off rarely or never consuming fermented foods.
Personally, I consume fermented foods (mostly fermented vegetables) strategically, in the sense that I use them to diversify my microbiome, as well as add them to my diet at times when I feel my gut health is compromised, which may for example occur if I take in a lot of salty foods, have been under a lot of stress, or have recently indulged a desire for fast food.
Key takeaway points:
- It’s an evolutionarily novel behavior for a human being to regularly consume large quantities of fermented foods. The ancient, preagricultural diets that over millions of years acted as selective forces upon the human genome contained primarily fresh food. This, in combination with various other pieces of Darwinian intelligence, suggests that it may be unwise to consume a lot of fermented foods on a regular & indefinite basis.
- Healthy people who harbor a diverse, resilient gut microbiota don’t necessarily have to consume fermented foods of any kind.
- Sick people who harbor a dysbiotic gut microbiota should strongly consider incorporating traditionally fermented vegetables into their diet. A lot of modern humans are in poor health and harbor a damaged gut microbiota; hence, a lot of people can undoubtedly benefit from consuming small quantities of a diversity of traditionally fermented vegetables, at least until their gut health has improved.
- Fermented vegetables can help one recover following acute gut perturbation caused by for example antibiotics, food poisoning, or fast food consumption.