Dear Doctor: I know what probiotics are, and I’ve heard of prebiotics. Now there’s supposed to be something called postbiotics? What are they, and why do they matter? Sometimes it seems like this whole microbiome thing is a scam.

Dear Reader: We hear and understand your skepticism. The discussion about probiotics, prebiotics and the gut microbiome has exploded in recent years. Along with the reputable research and findings that keep the topic in the news, we’ve been flooded with all sorts of sales pitches for a dizzying array of probiotic products and cures. (Probiotic clothing, anyone?) It brings to mind the early days of the gluten-free trend. Manufacturers of products that never contained gluten in the first place — such as almond butter, popcorn and even water — suddenly began carrying gluten-free labels. The result is a lot of noise that can obscure an important topic.

Let’s start with a review of the basics. A microbiome is a unique community of microbes that are living together in a particular habitat. Microbiomes are found not only in and on the human body, but also in the world around us. This includes animals, plants, plant communities, the soil and bodies of water. Our homes, our workplaces and even our cars can each have their own unique microbiomes. When it comes to humans, we have distinct microbiomes in locations all over our bodies. Areas such as armpits, the scalp, our skin, feet, mouth and our navels all play host to unique collections of microbes. These days, though, the word microbiome has become a sort of shorthand that refers to the trillions of beneficial bacteria, fungi, protozoa and viruses living in our gut. And that’s where the terms that you’re asking about come in.

As we’ve discussed here before, the word probiotics refers to the beneficial microbes found in certain fermented foods and beverages, as well in specially formulated nutritional supplements. Prebiotics are the indigestible carbohydrates, typically soluble fibers and resistant starches, that serve as a food source for the tiny inhabitants of your gut microbiome. And now, as you point out, we’ve begun to hear about something called postbiotics. The term refers to the compounds that are created as microbes dine on those indigestible carbohydrates we just mentioned. Basically, postbiotics are the waste products of your gut microbiome’s metabolic activity. That means that any fermented food that contains or was made by live bacteria contains postbiotics. That includes yogurt, kefir, sauerkraut, certain pickled vegetables, tempeh, miso, kimchi and kombucha.

As researchers began looking more closely at postbiotics, they came to suspect that these compounds have beneficial properties. Initial findings suggest that postbiotics may play a role in maintaining a balanced and robust immune system, support digestive health and help to manage the health of the gut microbiome. There is also evidence that postbiotics may help to lower inflammation, and may have a role in improving the regulation of blood sugar levels.

Rather than thinking in terms of supplements, add some fermented foods to your diet. And don’t forget the fresh fruits, vegetables and leafy greens that are keeping the trillions of microbes in your gut healthy and happy.

Eve Glazier, M.D., MBA, is an internist and associate professor of medicine at UCLA Health. Elizabeth Ko, M.D., is an internist and assistant professor of medicine at UCLA Health. Send your questions to askthedoctors@mednet.ucla.edu, or write: Ask the Doctors, c/o UCLA Health Sciences Media Relations, 10880 Wilshire Blvd., Suite 1450, Los Angeles, CA, 90024. Owing to the volume of mail, personal replies cannot be provided.