Probiotics & Prebiotics: Do We Need Both for a Healthy Gut?

You are what you ~~eat~~ feed your trillions of microscopic gut bugs. Okay, that may not sound very pleasant. But it’s true.

Gut health is a popular topic these days. The buzz words microbiome, probiotic, and prebiotic are taking over everything from shelves in the grocery store to ads on our phones. With all this attention, we know you may have some burning questions—and we’re here to answer them.

Maybe you’re a skeptic—we were fine before the days of kombucha, so do we really need to worry about probiotics for gut health now? Or perhaps you’re a seasoned pro looking to clear up a few details: Is it better to consume prebiotics or probiotics—and which is better—a probiotic food or a probiotic supplement? Even if you’re new to the conversation, wondering, wait, what are prebiotics again? We see you, and we’ve got you covered. As always, let’s take it from the top.

Probiotics & Prebiotics: How They Differ

Put simply, probiotics are the good bacteria, while prebiotics feed the good bacteria. Before we dive into the details of each, let’s back it up a few steps and talk about those trillions of gut bugs of yours—collectively known as your microbiome.

The human gastrointestinal tract is home to over 1,000 species of microbes. These mainly consist of bacteria, but also fungi, viruses, and yes—even parasites.¹ Generally speaking, the bacteria that reside in our gut are a combination of non-pathogenic (good or beneficial bugs) and pathogenic (bad or harmful bugs), with the majority of gut bacteria being beneficial. Most of the bacteria that inhabit the gastrointestinal tract foster a symbiotic relationship that benefits both the bacteria and the human host. One well-known example of a harmonious relationship between humans and gut bacteria is fiber digestion. Humans are incapable of digesting fiber on our own, so the bacteria in the gut take on the job for us! In exchange, the gut bugs consume the fiber, which results in the production of short-chain fatty acids (SCFAs), which have numerous documented benefits in humans (we’ll dive deeper into this later). Stress, environmental factors, genetics, and diet all affect this balance—influencing everything from your immune system² to your mental health.³

Modern research has shown us that a low level of bacterial diversity (known as gut dysbiosis) makes it difficult for the gut to function properly.⁴ In other words, when the bad bugs outnumber the good, we’re in trouble!

What are probiotics?

Probiotics are living strains of bacteria and yeasts that benefit their host when consumed.⁵ In other words, probiotics add to your gut’s microbial diversity. Some people choose to focus on probiotic food sources, like sauerkraut or kimchi, while others opt for supplements containing billions of beneficial microbes. There are hundreds of beneficial microbe strains being studied today, but there are seven common species that you will often see on any given probiotic supplement label. These include Lactobacillus, Bifidobacterium, Saccharomyces, Enterococcus, Streptococcus, Escherichia, and Bacillus.⁵ You will also likely see colony forming units or CFUs on the label, representing the number of live microbe strains in each dose.

Benefits of probiotics

Research on probiotic consumption is ongoing, but according to the Academy of Nutrition and Dietetics, “evidence-based reviews indicate that certain strains of probiotics contribute to the microbial balance of the gastrointestinal tract, supporting the immune system and reducing inflammation of the gut.” Research broadly supports the use of probiotic supplements for the prevention of respiratory infections and antibiotic-associated diarrhea as well as traveler’s diarrhea.⁶ Finally, there is some evidence that increasing probiotics consumption through either a food or supplement source may improve digestion and absorption of nutrients.⁷

What are prebiotics?

Prebiotics, on the other hand, are non-digestible food ingredients that feed and strengthen beneficial gut bacteria when consumed.¹ These include beta-glucans, fructooligosaccharides, and galactooligosaccharides (try saying those five times fast), among others. Such prebiotics are found in many foods such as apples, oats, and onions. Like probiotics, prebiotics come in supplement form too. These will often be offered in combination with a probiotic and referred to as a synbiotic or, less commonly, as a standalone product.

Benefits of prebiotics

As mentioned previously, prebiotics like fiber pass through the intestines undigested and become food for probiotic microbes to ferment. Some of the resulting byproducts of the fermentation process are SCFAs—those metabolites that boast impressive benefits like reducing inflammation and having anti-tumor effects.⁸ One SCFA in particular, butyrate, can’t be produced without adequate prebiotic consumption.⁹ Production of SCFAs isn’t the only benefit of prebiotic consumption, though. Prebiotics have also been shown to affect gut barrier function and alter bacteria subpopulations.¹⁰

Probiotics & Prebiotics: Food Sources

Probiotic Food Sources	Prebiotic Food Sources
Sauerkraut	Oats
Miso	Barley
Kimchi	Jerusalem artichoke
Sourdough bread	Bananas (unripe)
Pickles (unpasteurized)	Garlic
Kombucha	Onion
Yogurt	Dandelion greens
Kefir	Legumes

The bottom line: should I take probiotics and prebiotics?

Everyone’s microbiome is unique to them. Thus, probiotics and prebiotics will interact with your unique gut bacteria in a different way than, say, your coworker. There is still much that remains to be uncovered about the human microbiome as a whole. However, diversifying your diet to include natural probiotics and prebiotics from food sources such as those mentioned above is a great way to diversify your gut bacteria and, therefore, your overall health.¹¹

Before adding a prebiotic or probiotic supplement one should always consult with their doctor or a registered dietitian.¹²

Cheers to your next probiotic and prebiotic-rich meal to strengthen those powerful microscopic gut bugs (okay, we’re doing it again—that didn’t exactly stimulate the appetite, but you get it).

To learn more about Fy Protein, watch “science communicator and professional internet guy” Hank Green break it down here!

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1. https://www.hsph.harvard.edu/nutritionsource/microbiome/

2. https://www.nature.com/articles/s41422-020‑0332‑7

3. https://pubmed.ncbi.nlm.nih.gov/31530002/

4. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4425030/

5. https://ods.od.nih.gov/factshe…

6. https://www.jandonline.org/article/S2212-2672(13)01298–7/fulltext

7. https://my.clevelandclinic.org/health/articles/14598-probiotics

8. https://www.sciencedirect.com/science/article/abs/pii/S175646461630175X?via%3Dihub

9. https://journals.asm.org/doi/10.1128/mbio.02566–18?permanently=true

10. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3705355/