The human microbiome is shrinking (1, 2). It has been for quite a while (1, 2, 3, 4). Not only have we, via our modern diet and lifestyle behaviours, altered the configuration of our microbiotas, but we’ve also caused a loss of biodiversity from the human superorganism. These changes have contributed greatly to fueling the development of the chronic disease pandemic that lies like a thick, grey fog over our world.
There are many reasons why industrialized humans carry less biodiverse microbiomes than hunter-gatherers and traditional people. In the media and the blogosphere, a lot of attention has been devoted to the impact that antibiotics and processed, low-fiber diets have on our microbiotas. Less attention has been given to the presence, or lack thereof, of bacteria and other microbes on the foods we eat. The microbes that are found in fermented foods such as kimchi and sauerkraut are certainly talked about a lot, but other types of food-born bugs, including those that cling to fresh fruits and vegetables, have stayed largely out of the spotlight.
I think it’s time that these critters are given a more prominent spot on the microbiome stage.
Raw plant foods harbor many different types of bacteria, some of which can enhance your health
Our hunter-gatherer forebears didn’t take antibiotics, they didn’t eat highly processed foods, and they didn’t spend 90%+ of their lives inside closed buildings and cars. Also, unlike us modern humans, they didn’t eat clean, “sterile” food. They were regularly exposed to bacteria that cling to raw plant foods, as well as microbes that were present in the intestines and on the skin of the animals they killed.
We live in a very different environment than our ancient forebears; hence, we’re not necessarily best off replicating every aspect of their lifestyle. With that said, we can obviously learn a lot about diet and health from studying the behaviours and lives of our ancestors. There’s no doubt in my mind that one of the reasons why hunter-gatherers and other non-westernized people harbor a more diverse mix of microbes and other critters in their guts is that they are exposed to a lot of microbes on a daily basis via the food they eat.
In the developed world, we go to great lengths to limit the number of microbes we are exposed to via food. We infuse pesticides and antimicrobial substances into our food production system and we wash, clean, and/or heat much of the food we eat. Moreover, we eat a lot of highly processed foods, such as pizza, Cheerios, doughnuts, and chocolate chips, all of which are very sterile with respects to their bacterial content.
These practices help limit our exposure to potential pathogens; however, they also limit our exposure to microbes that can do us good. I would never recommend anyone to completely stop worrying about food-borne pathogens and never wash or clean any of the foods they eat. After all, as pointed out earlier, we have to consider our current circumstances when we decide how to live our lives in the healthiest possible way.
With that said, I think we would be wise to get more microbes into our diets. After all, we evolved on a “dirty” diet. We need to be exposed to microbes, preferably on a regular basis, or else, our microbiomes and immune systems suffer. As long as we are smart about which foods we eat raw and which we don’t, and specifically seek out foods that potentially harbor many friendly bacteria, we are on safe grounds.
There’s a lot of overlap with respects to the types of microbes that colonize the guts of animals and the roots of plants (5). Raw fruits and vegetables have always been an important part of the human diet and have contributed to shaping the human microbiome.
Some plant foods harbor a lot more friendly bacteria than others
One of the tips that are listed in the microbiome restoration plan is to eat fresh, raw plant foods derived from a trusted source. I think a lot of people underestimate the value of this tip. Most people understand that it’s important to eat healthy, fiber-rich foods and stay away from antibiotics. Most folks also understand that fermented vegetables can help them diversify their microbiome.
In some ways, raw plant foods are actually superior to fermented plant foods with respects to the microbes they harbor. They don’t harbor as many microbes in total as fermented foods (far from it), but that’s not necessarily a bad thing. As I’ve pointed out many times here on the site in the past (e.g., here, here), fermented foods such as kimchi, kefir, and sauerkraut are novel additions to the human diet. They contain a lot of bacteria, a lot more than any of the foods that were a part of preagricultural human diets (the only exception may be animal gut tissues, which may have been a part of the diet of some ancient humans). They also contain quite a bit of histamines. A very high intake of these foods can do more harm than good, in the sense that it can destabilize the gut microbiota and potentially cause some allergic reactions. These issues don’t apply to raw fruits and vegetables, which host much smaller quantities of microbes. Not only that, but raw plant foods may actually contain a greater diversity of microbes than fermented plant foods, seeing as many bacteria don’t survive in the acidic environment that is characteristic of fermented plant foods.
As this point, you may be wondering whether the tip of today’s article is simply the same as the one that is listed in the microbiome restoration plan, which is to eat fresh, raw plant foods derived from a trusted source. It isn’t. The key point I want to get across with today’s article is that some plant foods are a lot more useful in the context of microbiome restoration than others.
Raw cabbage is a particularly rich source of bacteria
One vegetable that is particularly interesting with respects to its microbiota is cabbage. There’s a reason why cabbage is the starting material from which sauerkraut, kimchi, and many other fermented vegetables are produced. Cabbage hosts many different types of bacteria, including the lactic acid-producing bacteria that give sauerkraut its acidic taste (9). The good thing about cabbage is that most of its leaves are not washed or directly sprayed with pesticides or other similar substances. As long as you remove the outer leaves of the cabbage before you start eating it, you’re all good.
Another thing that’s good about cabbage is that it’s available in supermarkets and health food stores all over the world. Also, it’s very cheap and doesn’t spoil easily. The compact nature of cabbage and its high Lactobacillus content help keep pathogens at bay. With that said, it’s obviously important to choose a high-quality product. My advice would be to seek out and buy the freshest cabbage you can find, preferably an organic product produced by a trustworthy company or farmer. It’s a good sign if the cabbage tastes fairly acidic, as it likely means that it harbors many lactic-acid producing microbes.
To be clear, I’m not advocating anyone to eat very high quantities of raw cabbage every day. Furthermore, perhaps needless to say, by itself, eating cabbage is not going to provide you with a diverse, flourishing gut microbiota. It’s not the end all be all of microbiome restoration; it’s merely a simple action you can take that will potentially bring some new microbes into your gut. There are no magic bullets or quick fixes that can equip you with a healthy microbiota for life. Rather, microbiome restoration and maintenance are multifaceted processes.
Many of the microorganisms you are exposed to via the consumption of food never make it past the acidic barrier in your stomach; however, some do. Some of these again may find an available niche deep down in your gut and become a permanent part of the superorganism that is you. Keep in mind, it doesn’t take trillions of microbes to make a difference. A single microbe that passes into your intestine can potentially multiple and become a major player in your gut.