What Are Prebiotics?

You know about probiotics, but what are prebiotics? Boosting your microbiome with probiotics-beneficial bacteria found in yogurt, kefir, kimchi and sauerkraut-has been shown to have health benefits, such as improving digestion, immune health and mood. But prebiotics-the nutrients in food that feed your gut bacteria-may be the next rising microbiome star. "We probably don't even realize when we're eating them," says Andrea Azcarate-Peril, Ph.D., director of the Microbiome Core Facility at the University of North Carolina at Chapel Hill. "However, in the near future we'll be hearing a lot more about how they can improve gut health."

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Do Probiotics Colonize My Gut?

Claims that probiotics colonize your gut imply that good bacteria displace the bad ones in your digestive tract permanently. That's not the case. Probiotics modify your microbiota temporarily. Think of these bugs as helpful tourists, dropping in and doing good things while they pass through before taking the G.I. highway out of town. (True colonization-where bacteria move in for good-happens in infancy.) Stop consuming probiotics and your micro-biome will shift back in a few weeks.

Prebiotic-Rich Foods

So, I'm stuck with the gut I've got? Not necessarily. You can improve your microbiome by encouraging the good bacteria you already harbor to grow with prebiotic foods:

• Wheat
• Walnuts
• Asparagus
• Jerusalem artichokes
• Bananas
• Legumes
• Onions
• Garlic

How Prebiotics Shift Your Microbiome

Prebiotics aren't one type of nutrient, but rather any compound that feeds your microbiome. This includes indigestible carbs (like inulin, found in wheat, and resistant starch, in legumes) and also polyphenols (plant compounds with antioxidant properties, like those found in walnuts). While prebiotic supplements do exist, experts recommend getting them from food, since they may work synergistically with other plant compounds.

When you eat these foods, your good gut flora feast on the prebiotics and multiply. This crowds out bad bugs and makes the good guys produce short-chain fatty acids, substances that may help control appetite, bolster immunity and even protect against cancer.

What's Better: Probiotics or Prebiotics?

It's too soon to say if one is better than the other. Plenty of research supports embracing probiotics -they can introduce strains of helpful bacteria that your gut may be lacking, at least temporarily. But know that it's not the only way to promote gut health. Regularly feeding the microbes you already have with prebiotics is also key.

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