The Best Sources of Prebiotics to Feed Your Good Gut Bacteria

These are the best sources of prebiotics. Learn which foods nourish both you and your healthy gut bacteria.


All that dirt under your fingernails and the sweat on your face are worth it.

Digging, planting, watering. Everything is done – even fertilizing. You can”t wait to see the fruits of your labor. Little shoots turn into little buds, and then into full beautiful flowers bursting with color.

Unless you feed your healthy gut bacteria the right foods, you’ll encourage the growth of the unhealthy microbes too. That’s why you need to know the best sources of prebiotics.

may all your weeds be wildflowers

Photo credit: Sandy Millar

Uh oh.

What if that fertilizer nourished all growing things – not just the flowers you envision in your happy place? What if ugly, prickly weeds flourished too?

That wrong kind of flourishing can happen in your gut too!

What are prebiotics?

In short, prebiotics are food for the good bacteria in your gut. The trillions of bacterial cells taking up residence in your colon need nourishment. They ferment various fibers from your diet to thrive.

But not all fermentable fibers are prebiotics.

Prebiotic food sources including onions, garlic, oats and edamame

Onions, oats, garlic, and edamame beans are sources of prebiotics.

That word – prebiotic – gets tossed around a lot. But it has a specific meaning. According to the International Scientific Association for Probiotics and Prebiotics (ISAPP), a compound in food (or a supplement) is a prebiotic only if it meets two criteria:

  1. It is selectively used by beneficial microbes
  2. It results in a known and measurable health benefit

In other words, a fiber or other compound fermented by random microbes with poorly-defined health benefits is not a prebiotic. A prebiotic is consumed by a small number of microbes, and because those microbes have a nourishing meal, you get a (known and measurable) health benefit.

How prebiotic foods act as fertilizers

Unfortunately, many food labels claim prebiotics are under the wrapper, but they aren’t true prebiotics unless research demonstrates a health benefit.

At a sponsored conference, Randal K. Buddington, Ph.D., director of the Prematurity and Perinatal Research Program at the University of Tennessee Health Science Center gave a fascinating talk about prebiotics and gut health. Here’s what he said:

“Some fertilizers stimulate the growth of everything, including weeds. Prebiotics are like selective fertilizers. They stimulate the growth of just the desirable bacteria that have the ability to use prebiotics.”

He went on to explain that in the same way healthy grass discourages the growth of weeds, prebiotics may decrease harmful bacteria by helping the beneficial microbes survive and thrive.

Interested in probiotic supplements? Check out how to pick the best probiotics.

What are the best sources of prebiotics?

Plant slant is the way to go because diets with lots of fiber-rich foods contain more prebiotics than other eating patterns. Here are some of the best sources of prebiotics.

  • onions
  • garlic
  • oats
  • bananas
  • soybeans
  • Jerusalem artichokes (also called sunchokes)
  • asparagus
  • wheat

For our babies, breast milk naturally contains prebiotics to spur the growth of beneficial microbes in the infant’s gut. Some baby formulas have added prebiotics.

And speaking of added prebiotics …

Added prebiotics in food

Here’s the list of compounds that the ISAPP identifies as prebiotics (meaning they selectively feed the good bacteria and there’s a known health benefit). Look for these in the ingredients list.

  • Galactooligosaccharides (GOS)
  • Fructooligosaccharides (FOS)
  • Oligofructose (OF)
  • Chicory root
  • Inulin

Chicory root and inulin are the same thing. You might see either term on food labels.

Food manufacturers frequently add chicory root (inulin) to yogurt, cereal bars, breakfast cereals and baked goods. Though it does help us fill the huge fiber gap (generally Americans eat waaaaay too little fiber), some people don’t tolerate it well in large amounts or when they first start eating it.

Why does chicory root cause bloating?

Because chicory root is not fully and rapidly fermented in the gut, large doses may cause gas and bloating in some people. Some people are even bothered by small doses. Experts suggest building tolerance by adding just a couple of grams of chicory root at a time until you can enjoy the amount in a full cereal bar or other product. For example, you might eat a small amount of a Fiber One bar every day for some time until you can eat a little bit more and a little bit more, and until finally, you can enjoy a whole bar without discomfort.

Why YOU should care about the best sources of prebiotics

Though research continues to grow and evolve, some known benefits of prebiotics are these:

  • stimulation of immune function
  • inhibition of harmful microbes
  • improvements in blood cholesterol levels
  • greater insulin sensitivity (think better blood sugar control)
  • better absorption of minerals
  • improved cognition
  • improvements in appetite control and weight management

The dose matters when it comes to health benefits. A bit of onions on your burger or some oats for breakfast now and then won’t cut it. According to Buddington, you may need from 5 to 12 grams daily depending on your health goals.

Learn about other factors – like antibiotics and different foods – that help or hurt your microbiome.

Bottom line: Eat tons of plants, especially fruits and vegetables. Feel okay filling in the gap with products containing added prebiotic fibers.

Eat well to help the healthy bacteria thrive like beautiful flowers in your garden.

As I noted above, prebiotics potentially boost your health in lots of ways, including blood sugar management if you have insulin resistance. Learn more about what to eat with prediabetes with my free guide.

Can I Eat That with Prediabetes?

It covers 10 foods you’ll want to know about.

Jill-Weisenberger_about-image-2
Jill Weisenberger

I'm Jill, and I believe simple changes in your mindset and health habits can bring life-changing rewards. And I don't believe in willpower. It's waaaay overrated. As a food-loving registered dietitian nutritionist, certified diabetes care and education specialist and certified health and wellness coach, I've helped thousands of people solve their food and nutrition problems. If you're looking for a better way to master this whole healthy eating/healthy living thing or if you're trying to prevent or manage diabetes or heart problems, you'll find plenty of resources right here.

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2 Comments

  1. Ruthielil on March 31, 2021 at 5:42 pm

    Hi Jill,
    Are there RDA servings of the prebiotic rich foods to eat? That is, is a prebiotic rich amount of onion 1 Tbsp — or 1/2 C? Does it matter if the vegetables or grains are cooked when it comes to prebiotics?

    I’d love to try sunchokes, but I can’t find them fresh or frozen anywhere in my local Canadian supermarkets. Grr. Do white potatoes qualify as a sunchoke substitute when it comes to prebiotics?

    • Jill Weisenberger on April 1, 2021 at 11:51 am

      Potatoes that have been cooked and cooled have resistant starch, another type of fiber that the good bacteria can use, and in the process, produce beneficial compounds. So yay for potato salad. Some experts recommend a minimum of 5 grams of prebiotics per day, but there are no RDA amounts and no specified serving sizes. To me, the key messages are to eat a very broad variety of plant foods, and most of us need much more fiber (of all types) than we’re getting. Sunchokes are in season through spring, so you may still be able to find them. they’re ugly but delicious!

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Jill Weisenberger

I believe simple changes in health habits can bring you life-changing rewards.

And I believe willpower is way overrated.

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