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What Foods are the Best Sources of Prebiotics?

What foods have prebiotics?

Everyone is talking gut health these days! You know about the microbes in your gut, and you’ve probably heard of probiotics in your food or supplements. But what about prebiotics?

Prebiotic food sources including onions, garlic, oats and edamame

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

What are prebiotics?

In short, prebiotics are food for the good bacteria in your gut. The trillions of bacterial cells that take up residence in your colon need nourishment too. The microbes ferment various fibers from your diet to thrive. But not all fermentable fibers are prebiotics. That word – prebiotic – gets tossed around quite a lot. But it actually has a very 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 that is fermented by a large number of microbes with poorly-defined health benefits does not meet the ISAPP definition of a prebiotic. A prebiotic is used by a small number of microbes and because those microbes have a suitable meal, you get a health benefit.

So even though a food label may claim that prebiotics are under the wrapper, it’s not truly a prebiotic unless there is research to demonstrate a health benefit.

At a sponsored conference earlier this year, I heard Randal K. Buddington, PhD, director of the Prematurity and Perinatal Research Program at the University of Tennessee Health Science Center give a fascinating talk about prebiotics and gut health. He’s a master of analogies. 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 that healthy grass discourages the growth of weeds, prebiotics may decrease harmful bacteria by helping the beneficial microbes to survive and thrive.

I’ve previously written about the microbiome and how to eat to help out those guys in your gut. I’ve also written up a thorough interview about picking the best probiotics. Be sure to check out both of these previous posts.

Best sources of prebiotics

You’ve already heard me say that the best diets have a plant slant and include a lot of variety. One of the benefits to such a diet is that it contains more prebiotics than other eating patterns. Here are some foods with known prebiotics.

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

And for our babies, breast milk naturally contains prebiotics to spur the growth of beneficial microbes in the infant gut. Some baby formulas have added prebiotics. And speaking of added prebiotics …

Added prebiotics in food

Here is the list of compounds that the ISAPP identifies as prebiotics (meaning that 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

By the way, chicory root and inulin are really the same thing, but either term may be on food labels.

Food manufactures 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 at first or in large amounts. Because chicory root is 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 everyday for sometime until you can eat a little bit more and a little bit more, and until finally, you can enjoy a whole one without discomfort. In this way, some packaged foods are among the best sources of prebiotics.

Potential health benefits of prebiotics

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

  • stimulation of immune your function
  • inhibition of harmful microbes
  • improvements in blood cholesterol levels
  • greater insulin sensitivity
  • 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 your health goals. So my best advice for this is to eat tons of plants, especially fruits and vegetables and to feel okay about using some products with added prebiotic fibers.

Jill Weisenberger

Jill Weisenberger, MS, RDN, CDE, CHWC, FAND, is a Nutrition, Culinary & Diabetes Expert, Wellcoach®-certified health and wellness coach, Freelance Writer, Registered Dietitian Nutritionist and Certified Diabetes Educator. She's also the author of four books, including a best-seller. She's a nationally-recognized media expert in high demand for print and online interviews, as well as corporate and one-on-one nutritional counseling. Jill's philosophy is that nutrition science should be understandable, realistic and oh so delicious.

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Like most of my patients and clients, I lead a busy life. You probably do too. Fortunately, you don’t need weeks, days or even hours to start living better and healthier. This blog offers timesaving strategies and bite-sized nutrition and health information. Come by often for tips and inspiration to healthy living – no matter how busy you are. I am a registered dietitian nutritionist offering credible, practical nutrition advice to keep busy people healthy. Yes indeed, we can be both busy and healthy.

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