Gut Bites MD

Christopher Damman, Associate Professor of Gastroenterology, School of Medicine, University of Washington. Editor-in-Chief of Gut Bites MD.

Too many “-biotics“

The field of gut health is filled with various “-biotics,” and it can be challenging to keep them straight. Here’s a simple analogy: think of your gut as a garden. Prebiotics are the fertilizer that feeds the garden, probiotics are the seeds you plant, and postbiotics are the beneficial nutrients the garden produces, which help the soil stay healthy and support a thriving ecosystem.

Postbiotics, a promising newcomer in the biotics category, may offer significant potential for addressing diseases linked to imbalances in the gut microbiome. A dysbiotic microbiome, which is an unhealthy balance of gut bacteria, can contribute to gut-related diseases and is also connected to metabolic, neurological, and immune disorders throughout the body.

Dysbiotic microbiomes often arise from chronic consumption of processed foods, overuse of antibiotics, stress, and lack of exercise. Sometimes, these imbalances become so entrenched that simply reintroducing healthy food is not enough to restore the microbiome.

Enter postbiotics

This is where postbiotics might be particularly helpful. They can serve as a stopgap to provide health benefits throughout the body and, importantly, can also act as a type of prebiotic to help regenerate a healthy microbiome.

Though “postbiotics” might sound like a new and complex term, it simply refers to the molecules and non-living cell components produced by the microbiome that promote bodily health. Our microbiome takes the leftovers in our gut—components like fiber and phytochemicals that we can’t digest—and converts them into bioactive molecules that can be absorbed and impact both the gut and distant parts of the body.

For example, our microbiome transforms fermentable fibers into short-chain fatty acids like butyrate, propionate, and acetate, which play crucial roles in regulating metabolism. It also converts polyphenols into more absorbable and potent molecules that similarly regulate metabolism.

Butyrate is a well-known postbiotic linked to various health benefits. For instance, in a pediatric trial, butyrate was shown to improve obesity, although studies in adults are still needed. Another postbiotic, Urolithin A—derived from the polyphenol ellagitannin—has been extensively studied and shown to improve muscle mass and endurance in middle age, with other potential benefits for cognitive decline and Alzheimer’s disease.

While these are conventionally known postbiotics, there are others not typically categorized as such, like conjugated linoleic acid, which has been studied for weight loss, and microbiome-derived indoles which have been evaluated for their anti-aging properties.

All these molecules are primarily produced by our gut microbiome, reinforcing postbiotics’ reputation as a type of natural pharmacy. Undoubtedly, there are still many more human microbiome postbiotics to be discovered and evaluated.

The postbiotics in fermented foods

However, our gut microbiome isn’t the only source of postbiotics. They are also produced by other microbial communities, such as those in fermented foods. Many of the same molecules—like modified polyphenols, B vitamers, conjugated fats, and carbohydrate products like lactate and acetate (also known as vinegar)—can be produced by fermented foods.

Fermented foods have been shown to positively impact gut health by increasing microbial diversity and reducing systemic inflammation. It may be the postbiotics present in these foods, as much as the live organisms themselves, that are responsible for these effects. Notably, the microbes that increase with fermented food consumption are often those already present in the gut, rather than those introduced by the fermented foods.

Acetic acid is a prime example of a postbiotic found in fermented foods and has gained attention through apple cider vinegar. Studies have shown that vinegar, even without the apple cider, can promote weight loss, potentially by slowing glucose absorption and preventing insulin spikes.

Fermented plant-based foods can also enhance modified polyphenols, making them more bioactive and bioavailable, thereby benefiting both gut and overall health.

Postbiotics and future research

Using postbiotics in combination—such as urolithin A with butyrate and acetate—might be particularly effective since they target different mechanisms, making this a promising area for future research. Gaining a better understanding of how they impact mitochondrial health through synergies in epigenetic regulators like HDAC and SIRT1 will also provide valuable insights into their roles in health.

In the meantime, while research on postbiotics continues, a diet rich in fermented foods might be especially beneficial in helping to restore a healthy microbiome. This could make traditional healthy foods like nuts, seeds, beans, fruits, vegetables, and whole grains—high in fibers, polyphenols, and unsaturated fats—even healthier.

More Resources:

Gutbites.org — where you’ll find more practical food & microbiome digests to improve gut and overall health.

Gut Microbiome Nutrition Calculator — to help in gut healthy food choice and meal preparation.

MD-authored gut health literature digests and first-in-class food quality app to power you