Prebiotics vs Probiotics: What's the Difference?

Probiotics are live microorganisms, such as certain bacteria and yeasts, that may offer health benefits when you consume them in adequate amounts. Prebiotics are food for the helpful microbes already living in your gut, mainly certain types of fiber and other plant compounds. In short, probiotics add beneficial microbes, while prebiotics feed them. You’ll find probiotics in some fermented foods like yogurt and kefir, and prebiotics in foods like onions, garlic, oats, beans and slightly green bananas.

Your gut microbiome in a nutshell

Trillions of microbes live in your digestive tract, mostly in your large intestine. Together they’re called the gut microbiome. They help break down fiber your own body can’t digest, produce certain vitamins and other compounds, and interact with your immune system. Scientists are still learning how the microbiome affects health, and much of the research is early. What’s already clear is that diet, especially fiber, shapes which microbes thrive.

What probiotics are

The widely used scientific definition describes probiotics as live microorganisms that, when given in adequate amounts, provide a health benefit. Benefits depend on the specific strain, so a result found for one type doesn’t automatically apply to another.

Foods that may contain live microbes include:

• Yogurt and kefir labeled with live and active cultures
• Refrigerated, unpasteurized sauerkraut and kimchi
• Miso, especially when stirred in at the end of cooking rather than boiled
• Some aged cheeses
• Kombucha and certain other fermented drinks

Not every fermented food contains live microbes by the time you eat it. Sourdough bread is baked, and most shelf-stable pickles and sauerkraut are pasteurized or made with vinegar, so their microbes are no longer alive. They can still be tasty, nourishing foods.

Research suggests some probiotic strains may help with certain kinds of diarrhea, including some linked to antibiotics, but evidence for many other uses is mixed.

What prebiotics are

Prebiotics are compounds that beneficial gut microbes use as food, which can encourage their growth. Most are types of fiber, such as inulin, fructooligosaccharides and galactooligosaccharides, though some other plant compounds count too.

Because prebiotics are mostly fiber, this topic overlaps a lot with our guide to dietary fiber.

Prebiotics vs probiotics side by side

You may also see the term synbiotics, which describes products combining both. Eating them together, such as yogurt with oats and banana, is an easy way to cover both bases.

What about supplements?

Probiotic supplements are widely sold, but in the US most are regulated as dietary supplements, which means the FDA doesn’t review them for safety or effectiveness before they reach store shelves. Products vary in which strains they contain and how many live microbes survive until the expiration date. For healthy people, probiotics are generally considered safe, but people who are seriously ill or have weakened immune systems, and parents of premature infants, should talk with a doctor before using them. If you’re considering a supplement for a specific issue, ask your doctor which strain, if any, has evidence behind it.

Simple ways to support your gut

1. Eat a wide variety of plant foods, including vegetables, fruit, whole grains, beans, nuts and seeds.
2. Add a fermented food a few times a week if you enjoy them.
3. Increase fiber gradually to avoid gas and bloating.
4. Drink enough fluids.
5. If you have irritable bowel syndrome, know that some prebiotic-rich foods, like onions, garlic and beans, can trigger symptoms. A registered dietitian can help you find what works for you.

A plant-based eating pattern naturally supplies plenty of prebiotic fiber, and whole grains, covered in our guide to complex carbs, are another easy source.

The bottom line

Probiotics are live microbes that may support health, while prebiotics are mostly fibers that feed the helpful microbes already in your gut. You can get both from everyday foods: fermented foods like yogurt and kefir for probiotics, and onions, garlic, oats, beans and bananas for prebiotics. Food is the best starting point, and a doctor can help if you’re considering supplements.