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What Are Postbiotics and What Do They Need to Do With Intestine Well being?

Gut health is a huge issue that has just gotten bigger.

You know probiotics: bacteria that, when consumed, offer benefits for our intestines, our metabolism and / or general health. Some probiotic bacteria colonize our intestines – they colonize our digestive tract and ensure a lasting effect. Some probiotic bacteria are temporary – they visit and impart benefits and interact with our gut and its inhabitants, but they don’t stay.

You are also familiar with prebiotics: indigestible food components that nourish the bacteria living in our intestines and provide them with nourishment. Prebiotics include fermentable vegetable fibers, resistant starch, “animal fiber” and certain polyphenols.

This is standard material. Whole store shelves are devoted to fermented dairy products, cucumbers, sauerkraut, nutritional supplements, kombucha, and other sources of probiotics. You likely have all sorts of weird gums and fibers and powders that act as prebiotic substrates for intestinal bugs. Gut health is mainstream.

But you probably don’t know about postbiotics.

What are postbiotics?

Postbiotics are the products made by our gut bacteria after consuming prebiotics, interacting with incoming food components, and interacting with other bacteria. They include:

  • Short chain fatty acids such as butyrate, propionate and acetate
  • Vitamins like inositol, vitamin K2, and certain B vitamins
  • Neurotransmitters like GABA and serotonin

And then there are the probably myriad post-biotic effects, metabolites and results that we have yet to clarify and quantify.

In other words, postbiotics – the effects, products, and interactions of probiotic bacteria – are the only reason we’re so interested in probiotics and prebiotics.

Short chain fatty acids

The short chain fatty acids that are byproducts of fiber fermentation, including butyrate, propionate, and acetate, improve our health in many ways. Butyrate in particular has been shown to have beneficial effects on insulin sensitivity, colon transport, inflammation, and symptoms of Crohn’s disease. It is also the preferred source of fuel for our native colon cells. Without enough butyrate, our colon cells can wither and die, which can lead to indigestion and even cancer. In colon cancer patients, for example, mucin-degrading bacteria predominate, while in healthy patients without cancer, butyrate-forming bacteria dominate. Populations with lower colon cancer rates also tend to have higher butyrate levels.

Propionate is also helpful in reducing fat storage and improving lipids. One of the coolest effects, however, is exercise tolerance: certain gut bacteria have been shown to metabolize lactate into propionate, thereby improving physical performance. In fact, top athletes tend to have higher levels of propionate-producing bacteria in their intestines.

Acetate is less well characterized, but has been shown to improve butyrate production.


When gut bacteria consume substrates, they produce various metabolites, the best known of which are the short chain fatty acids butyrate, acetate, and propionate discussed in the previous section. But they also produce vitamins, especially vitamin K, B vitamins and inositol.

While this has not been directly quantified, we do know that the potential for gut bacteria producing vitamin K2 is there. The use of broad spectrum antibiotics leads to lower levels of vitamin K2 in the human liver, including: A consequence that only makes sense if the antibiotics kill bacteria that produce vitamin K2. What we produce in the intestine can certainly be absorbed and used.

And gene sequencing of strains of bacteria known to inhabit the human gut has found strong evidence of genetic ability to make folate and other B vitamins. However, these vitamin-producing genes are only expressed “when bifidobacteria are in their natural ecological niche”. You can’t feed on processed junk foods and refined grains and hope to feed the bacteria in question. If you want your gut bacteria to produce vitamins as postbiotics, you need to provide their “natural ecological niche” – prebiotics, good sleep, healthy living, colorful plants, sunlight, and exercise.

Certain gut bacteria can actually convert phytic acid into inositol, prevents the mineral-binding activity of phytic acid and releases the mood-regulating and insulin-sensitizing effects of inositol. The more phytate-rich foods you eat, the better your gut bacteria can break it down into inositol.


When scientists first discovered the enteric nervous system, which resides in the vagus nerve and runs from the intestines to the brain and back again, they assumed that it only provided information and instructions about digestive contractions. But now we know it’s much more than that. We know that gut bacteria produce 95% of our serotonin, half of our dopamine, and a significant portion of our GABA. This could explain why unhealthy gut biomes are strongly linked to mental health problems such as depression and anxiety, and we probably even have the concept of a “gut instinct”.

People with major depressive disorder are more likely to have low levels of Bacteroides, a type of bacteria known to produce large amounts of GABA in the human gut.

Should You Take Post Biotic Supplements?

Some companies have started to market post-biotic supplements like pure sodium butyrate and something called “yeast fermentate” which is the concentrated extract of brewer’s yeast fermentation. The butyrate and fermentate are probably okay, but this isn’t the best way to get postbiotics. It’s not the same as having your gut bacteria made by yourself.

I say this all along with regards to probiotics and prebiotics: instead of fixating on a single strain, metabolite, short chain fatty acid, or specific source of fiber, think in terms of whole foods, whole lifestyles, and health. There’s so much we don’t know about what’s going on in our gut – up to 65% of the bacteria that live in our gut haven’t even been cultivated and analyzed – and it’s silly to think we can get certain results achieve. For example, you can’t just mega-dose propionate and hope for performance gains in the gym, or throttle butyrate and lower your insulin resistance. It may work, but it probably works better to resolve the situation with a bottom-up approach that emulates or is the natural, organic route than adding an ingredient in the middle of the process.

That said, maybe postbiotic supplementation will improve across the board.

How do you support natural post-biotic production?

That’s a big question, but there are answers.

Eat prebiotics. This post gives a good overview of prebiotics and how to get them. And find out about resistant starch, a particularly butyrate-friendly form of prebiotics. Excellent sources of prebiotics are onions, garlic, leeks, Jersualem artichokes, asparagus, light green bananas, boiled and chilled potatoes, pistachios and almonds, chicory root, mushrooms, dandelion greens, and carrots. I could go on and the ones listed are the most potent sources, but you understand that plants contain prebiotics.

  • Eat probiotics. Eat fermented dairy products, eat fermented vegetables, take supplements if that’s easier or you want to supplement.
  • Eat colorful fruits and vegetables and animals. These plant pigments, polyphenols and animal connective tissue are prebiotic substrates for the intestinal bacteria.
  • Maintain good circadian hygiene. Sleep and circadian rhythms affect every system in the body, and the gut is no different.
  • Manage stress. Stress disrupts the intestinal bacteria and worsens intestinal health.
  • Play in the dirt. Spend time outside getting dirty.
  • Get some sun. Sunlight is another underrated modulator of the diversity of intestinal bacteria.
  • Eat whole foods. Whole foods contain the broad spectrum of food components, many of which we have not quantified and some of which have positive postbiotic effects on gut bacteria.

For a comprehensive treatment of all of the things that affect gut bacteria both positively and negatively, read this post.

As you can see, nothing is created with great specificity (“to produce” [this specific postbiotic], to do [this specific intervention] or take [this specific supplement]”). You can’t do just one thing. You need to take a comprehensive, holistic, primal approach. But here’s the great thing about it: not only do you get the benefits of postbiotics, but the health, fitness, and overall happiness benefits of living healthier in general, too.

About the author

Mark Sisson is the founder of Mark’s Daily Apple, godfather of the primal food and lifestyle movement, and New York Times bestselling author of The Keto Reset Diet. His latest book is Keto for Life, in which he discusses how he combines the keto diet with a primal lifestyle for optimal health and longevity. Mark is also the author of numerous other books, including The Primal Blueprint, which in 2009 was credited with accelerating the growth of the Primal / Paleo movement and maintaining optimal wellbeing, Mark founded Primal Kitchen, a real food company, the Primal / Makes paleo-, keto-, and Whole30-friendly staples.

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