Zombie Chefs & Their Meals for Us
Learn more about paraprobiotics and postbiotics
A couple of years ago, while on tour for our fermented legumes and grains book, we got a question from a woman in the audience who was frustrated with keeping her probiotic foods alive. “I’m not a rabbit,” she declared, “I like my meals cooked.” We had our pocket suggestions to such questions, like dropping in fermented foods at the end of a soup or as a side to that casserole bake, but for all we knew if she did tuck some sauerkraut in her roast and bake it the good microbes died and the probiotic value to us as the human in the equation, was lost.
This post is for that woman, and for you. We are going to talk about two new areas of scientific focus these days and they both are dead, and good for us. This would more likely be a better post on Día de Muertos and maybe someone can remind me around October to update it with what has been discovered in the future nine months.
Until then let’s look at what paraprobiotics and postbiotics are. We will look at how they are related to other -biotics that you might already know, why you should care.
You are the kitchen, they are cooks that live in your kitchen
In order for me to keep all of these straight I offer the following analogy with microbes, chefs, food and meals because I like all those things very much.
Let’s say that your gut is like your home kitchen, and the good gut bacteria in there are like you in your kitchen. You are cooking up something up to eat, which you probably have done a lot more of in the past year than ever. Like the commensal bacteria (the resident bacteria) in your gut, you are working with ingredients in your kitchen to make them more appetizing and healthier. Some meals are more complicated than others, taking longer and requiring you to process more ingredients. In the process you have waste, some of it goes in the garbage and some gets set aside to be composted. Or maybe you are grabbing a pre-made meal from the freezer and zapping it, with the only waste being the box. The same thing roughly is going on in our guts as our gut microbes. It’s like they are down their whipping up something tasty to eat with the groceries you sent down to them. What is left, or the waste generated in the process, is available to us (our bodies) if we can use it.
In a way we get their table scraps. It is a you eat something as the host and get some nutrition from it, then a little bit of it passes by to them, who eat it and benefit, producing in the process things that again benefit us. Imagine dumping your compost bucket in a bowl and coming out with a cake. If only…
Probiotics are bacteria that do this same thing but outside of us. They are like commercial chefs, turning ingredients into tasty dishes to be consumed, just like we do at home, just more focused.
Chefs know what they are making and they know exactly what raw ingredients they need to make those dishes. Your tiny microbe chefs also need raw ingredients. You can think of these raw ingredients as prebiotics. They aren’t chefs, they are the food the (tiny microbe) chefs need to do their thing.
This is a good point to say that for all of human history this was the story. Humans were born and received a starter set of microbes through that process. First foods augmented that microbiota to what was to come. Our microbes were strong, diverse, and good at dealing with what we were likely to put in our mouths.
When people eat some fermented foods they get both prebiotics and live probiotics, which is like inviting chefs to our home with all the ingredients they will need to make us a lovely meal. Like those hired chefs, probiotics rarely stick around for long, but they could have an influence upon how we, the resident home cooks, make a meal. That’s always been fine, because for mostly all of humanity our microbes were good at this, matched to what we as their host would choose to eat and in quantities they could handle. This isn’t the case anymore for most people—more on diet and microbiota diversity to our offspring in an upcoming post.
Now for the new terms. The microbial meal and all the ingredient waste is called postbiotics, or sometimes metabiotics or biogenics.1 Actually, to be truthful, it would include bits of dead skin cells and a stray hair or two from the microbial cooks. The analogy is far from perfect and its about to get worse than a stray hair in your meal but stay with me a bit more and I promise in the next part we will get into the science of all of these. Finally, we have paraprobiotics, which are also referred to as non-viable probiotics, inactivated probiotics or ghost probiotics, which would be in our analogy, dead chefs, or zombie chefs because they aren’t dead dead, just not alive either. More on that in a bit.
So, to bury this analogy (sorry) we can think of commensal bacteria in our guts as home cooks, taking some of the things we eat—prebiotics—and producing a number of things that make up the bulk of what we think of as postbiotics. Live bacteria that can do the same thing but are outside of us are probiotics, which when ingested can go about their work in our guts. To be considered a probiotic they have be proven to provide humans with a health benefit and they have to be in sufficient numbers to confer that benefit. They usually don’t stay around and eventually pass out the dark southern tunnel, so to speak. Dead probiotics, either dead on arrival to our mouths or dead on their journey through us, are referred to as paraprobiotics. While we are at it, we should probably mention synbiotics, which like post- and parapro- are fairly new terms that describes the combination of prebiotics and probiotics that convey benefits to our guts. Whew. Then if you have to take antibiotics everyone dies, seriously shifting probiotics and commensal bacteria to paraprobiotics I guess, until they all float down the dark tunnel and out the exit.
Postbiotics are products or metabolic byproducts that are either secreted by the microbes or are released when they die that conveys a beneficial effect on their host. The concept came about from the observations that the human benefits from the microbiota are mediated from the secretion of the metabolites.2 Some examples of the products and byproducts include short chain fatty acids (SCFAs), enzymes, peptides, functional proteins, vitamins and organic acids.1,3 I have seen definitions that state that to be a postbiotic this process needs to happen outside the human body. Think of sourdough bread for a moment. You have a bubbly overnight starter that you mix with flour, water and salt and allow to ferment all day long. The yeasts and bacteria and processing the carbohydrates, producing products and wastes. Then you throw that live community into a hot oven and all the microbes die or become deactivated to use a nicer term. Those postbiotic compounds are still there, still in that lovely sourdough slice that you cut off before its really cooled enough and dip in a nice olive oil.
I think what I was most surprised about when trying to understand postbiotics is that its not just about the main product that we all think of: lactic acid in fermented vegetables; acetic acid in vinegar; ethanol in beer, wine and ciders. It is everything else and together it plays a big health role. In the case of sourdough it’s also what sets it apart nutritionally from a bread process that doesn’t rely upon fermentation. Another way to think of it is that if you have an equation:
POSTBIOTICS = TOTAL BENEFITS - (PREBIOTICS + PROBIOTICS)
Why is this important? One reason is because not everyone can take prebiotics without adverse effects. My mom is one of those people. With very few exceptions when my mom takes the first bite of a probiotic-rich food, or even probiotics in pill form, you can start the countdown timer to abdominal pain and diarrhea. Its tough as someone in my fermentation love bubble, to see this food that only showers me with happiness cause so much pain in another, especially my mom. There are many, many people like her because we have met them over the past 6 years all around the world. For them, getting similar benefits to probiotics without the live microbes that can cause a number of issues is a safer way to start. Another way is paraprobiotics.
Paraprobiotics or Ghost Probiotics
Paraprobiotics refers to probiotics that have been inactivated, which is a nice way to say they cannot reproduce. Because paraprobiotics cannot reproduce themselves, they cannot overwhelm the microbiota balance in the gut, or imbalance for many. They also cannot cause the opportunistic infections, allergic sensitization or autoimmune disorders that are sometimes possible with probiotics.5,6 Zombies cannot out-compete the living, despite what zombie movies might say.
What’s it all mean?
If I had read this post and maybe followed a couple of the following links to go deeper before that woman asked her question I would have answered her differently. Thing is, only one of these articles was even published in 2017, a demonstration of how fast and fresh the research in this area really is. When the time comes when we can all meet in a place and talk about food and our favorite fermentation technique again, postbiotics and paraprobiotics will be part of that conversation because I think its that important. Even if most of us will never see a microbe in a microscope, nor deactivate villages of them, just knowing its more complex than “take a probiotic pill and you’re all good” I think is an important thing. We are complex, our guts are very complex, and we continue to learn about both all the time. Maybe that cider and a toasted cheese sandwich with homemade sourdough, good cheese and some kimchi cooked to melty goodness is better for you than you thought.
As always, thank you for your time reading this and please share your knowledge about the subject. We are all fermentation nerds and love to learn from each other. If you have a topic you would love to see soon just let me know.
Stay safe out there,
Citations and Further Reading
1 Aguilar-Toalá, J. E., et al. "Postbiotics: An evolving term within the functional foods field." Trends in Food Science & Technology 75 (2018): 105-114.
2 Żółkiewicz, Jakub, et al. "Postbiotics—A Step Beyond Pre-and Probiotics." Nutrients 12.8 (2020): 2189.
3 Şanlier, Nevin, Büşra Başar Gökcen, and Aybüke Ceyhun Sezgin. "Health benefits of fermented foods." Critical reviews in food science and nutrition 59.3 (2019): 506-527.
4 Russo, Edda, et al. "Immunomodulating activity and therapeutic effects of short chain fatty acids and tryptophan postbiotics in inflammatory bowel disease." Frontiers in immunology 10 (2019): 2754.
5 Taverniti, Valentina, and Simone Guglielmetti. "The immunomodulatory properties of probiotic microorganisms beyond their viability (ghost probiotics: proposal of paraprobiotic concept)." Genes & nutrition 6.3 (2011): 261-274.
6 Shenderov, Boris A. "Metabiotics: novel idea or natural development of probiotic conception." Microbial ecology in Health and Disease 24.1 (2013): 20399.