Your Definitive Guide to All the '-Biotics'

Dip one toe into the world of health and wellness, and you’ll be inundated with products advertised as containing one kind of “-biotic” or another, from “pre-” to “post-.” It’s not just in your head: These “biotics” have risen in popularity within mainstream culture thanks to recent advancements within the scientific realm. 

Microbiologists have been studying bacteria and their interactions with the human body for more than 350 years, but their attention has historically been focused on pathogens: the “bad” microbes that can cause disease. The past decade, however, has seen an explosion of scientific interest in the human microbiome—the community of microbes that live symbiotically with and within us—which is necessary for whole-body health. In 2010, the word “microbiome” showed up in a little over 6,700 scientific publications from that year, according to Google Scholar. In 2022, there were over 65,000 publications, connecting the microbiome to everything from obesity to cancer to schizophrenia. As the science has advanced, people and businesses have taken notice.

So what, exactly, do all those “biotic” terms mean? Here, we demystify the most common of them and (hopefully) help you become more informed about the products and foods you can buy, as well as the fascinating advances in science.

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1. Probiotics: Planting Seeds of Good Health

Much like a gardener plants seeds with the expectation that they’ll turn into flourishing plants, we introduce these beneficial microorganisms into our bodies with the hope they’ll prosper and benefit our health.

But the World Health Organization (WHO) has a pretty specific definition of probiotics, and describes probiotics as “live microorganisms that, when administered in adequate amounts, confer a health benefit on the host.”¹ While this could theoretically include many foods and products, from capsules to yogurts to fermented drinks, it’s worth unpacking what this definition requires—namely, that the product includes specific strains of bacteria which have been demonstrated to exert a health benefit in humans, and that your body receives enough of these beneficial microbes in a specific dose to actually make a difference in your health. In other words, it doesn’t really matter if a fermented drink contains bacteria, if they’re not the right type or there aren’t enough of them to provide any actual health benefits. That’s why a scientifically validated probiotic is your best bet if you want to reap the benefits of microbes. 

While an important part of the definition is that the microbes be alive, it’s not necessarily about these microbes colonizing or setting up permanent residence in the gut. Instead, like an annual plant rather than a perennial, they’re typically just passing through—doing good deeds along the way. They travel through your intestines—interacting with local cells, nutrients, and your resident microbes—to deliver health benefits, before they exit your system.

It’s also worth mentioning that the U.S. Food and Drug Administration considers probiotics and dietary supplements to be food, not drugs. While this limits the claims that can be made around what they’ll do for your health, it also means there’s much less oversight—part of why it’s important to dig into the science around any probiotic’s claim of health benefits in order to assess whether it’s likely to work for you.

2. Prebiotics: Fertilizing Our Internal Garden

ISAPP defines prebiotics as “substrates that are selectively utilized by host microorganisms conferring a health benefit.”² In simpler words, they’re food for our beneficial microbes—if probiotics are the seeds of our internal garden, prebiotics are their fertilizer. They nourish the “good” bacteria, helping them flourish, and sometimes these prebiotics even turn into health-promoting compounds with the help of those same microbes.

Here again, though, the definition is quite specific: ISAPP scientists have pointed out that not everything that feeds bacteria (even good ones) is a prebiotic. The defining characteristic is selectivity. Pure sugar can encourage the growth of “good” bacteria, but it can encourage the growth of harmful ones like E. coli equally well—so it can’t really be called a prebiotic. 

Many of the food ingredients that are marketed for their prebiotic potential are various kinds of fiber: the components of foods that your body can’t digest or absorb on its own, including prebiotics like inulin and fructo-oligosacharides (FOS), which are often added to foods in an effort to make them more microbiome-friendly. But the term “prebiotic” isn’t just a marketing tool—it also applies to whole foods and their components. For example, a fresh apple is most certainly a prebiotic.There are also plenty of food components that aren’t fiber, but which still meet the definition of a prebiotic—many of the antioxidants found in fruits and vegetables appear to exert at least part of their beneficial health effects with the help of certain gut bacteria. A prime example of this is punicalagin, a compound from pomegranate, which you’ll find in our DS-01® Daily Synbiotic.

3. Postbiotics: Harvest, Mulching, + Compost

Part of the magic of the microbiome is that it enables some remarkable chemistry to happen right inside our bodies: Everyday foods can be used by our bacteria to produce vitamins, essential amino acids, short-chain fatty acids (SCFAs), and other health-promoting compounds.^7,8 But sometimes, it’s best to let that chemistry happen outside the body—and that’s where postbiotics come in. A postbiotic, according to ISAPP, is “a preparation of inanimate microorganisms and/or their components that confers a health benefit on the host.”⁹  

“Inanimate” is the key word there—postbiotics are derived from bacteria that have been deliberately killed, often by a process like cooking. It’s a little like mulching your garden: Sprinkling a layer of dead plant matter can help keep weeds down, and offer unique nutrients to the soil. One advantage of this approach is that a postbiotic can confer some of the same health benefits as a probiotic, but is often a lot easier to produce, since keeping bacteria alive for long periods of time under various conditions is tough. (And you don’t have to worry about making sure the bacteria in a postbiotic stay dead.)

A postbiotic approach is also useful when the organism involved has beneficial properties, but might be unsafe if introduced alive. One great example is nutritional yeast. While it’s not bacterial, it is a microbe—and it’s probably the most widely used postbiotic on Earth. This flaky substance is a deactivated form of the same species of yeast that produces beer and wine. It’s rich in B vitamins and offers a vegan-friendly cheesy flavor to certain snacks. So why is it better to get this form of yeast as a postbiotic? No amount of vitamin B is worth the risk of a yeast colony setting up shop in your intestines and converting the carbohydrates you eat into alcohol—a known microbiome-disrupter.¹⁰ 

Another common postbiotic, which might surprise you: many vaccines. Oftentimes, vaccines contain an inactive version of a virus or bacterium, which helps the immune system get a handle on it without posing any real threat—and ultimately giving you immunity against it if you ever encounter it again (dead or alive).

4. Antibiotics: Pruning + Weeding

When the word “antibiotic” (literally meaning: “against living things”) was coined near the end of the 19th century, it was used to describe any substance which has a destructive effect on microbes, such as highly concentrated alcohol. (These days, the word “antimicrobial” is a better fit for the original meaning.) Antibiotics as we know them today—that is, “antibiotic” as a noun, rather than an adjective—weren’t discovered until decades later, when penicillin was first isolated from a fungal culture. 

There are now dozens of different kinds of antibiotics in clinical use, and they can be lifesaving tools: Just as it’s sometimes necessary to weed a garden to prevent an invasive species from taking over, these drugs can prevent microbial catastrophe. They’re typically highly potent, and—compared to antimicrobials like alcohol—selective in their activity, only killing certain kinds of bacteria. This selectivity is far from perfect, though, and even “narrow-spectrum” antibiotics still have the potential to cause problems in the gut microbiome.¹¹ Research has long shown that digestive diseases like Crohn’s are linked to antibiotic use, but more and more research also links the use of certain antibiotics to diseases beyond the gut, like Parkinson’s.^12,13

Knowledge is Agency 

It’s important to remember that these categories aren’t cut and dry, or mutually exclusive: A fermented food like kefir can count as all of the above, depending on how picky you want to be. But understanding the broad strokes can help you decide where you want to double-click, whether that’s because you’re trying to find a product that will work for you, or you’re just interested to learn more about the science that’s quickly shifting the way we view whole-body health. 

While it can be hard to keep up with the multitude of terms cropping up in this field, this proliferation is a manifestation of the need to name and understand things as we explore the potential of the human microbiome. It’s a powerful testament to people’s growing curiosity about—and respect for—the worlds within us.