Learn the difference between a probiotic and a prebiotic — and why you need them both.
By Mayo Clinic StaffYou are what you eat. Or more accurately, you are what you feed the trillions of little critters that live in your gut.
The lining of your gut, like every surface of your body, is covered in microscopic creatures, mostly bacteria. These organisms create a micro-ecosystem called the microbiome. And though we don't really notice it's there, it plays an oversized role in your health and can even affect your mood and behavior.
Not surprisingly, what you feed your microbiome may have the biggest impact on its health. And the healthier it is, the healthier you are. The key to a healthy microbiome is nourishing a balance among the nearly 1,000 different species of bacteria in your gut.
There are two ways to maintain this balance — helping the microbes already there to grow by giving them the foods they like (prebiotic) and adding living microbes directly to your system (probiotic).
Prebiotics
Prebiotics are specialized plant fibers. They act like fertilizers that stimulate the growth of healthy bacteria in the gut.
Prebiotics are found in many fruits and vegetables, especially those that contain complex carbohydrates, such as fiber and resistant starch. These carbs aren't digestible by your body, so they pass through the digestive system to become food for the bacteria and other microbes.
The list of prebiotic foods is long, from asparagus to yams. A quick internet search will yield dozens of examples, as will a consultation with a registered dietitian.
Nowadays, the list of prebiotic supplements might be even longer, but they usually contain a complex carbohydrate such as fiber. Supplement companies market products to specific conditions, such as bone health and weight management, claiming that their ingredients enhance the growth of specific kinds of bacteria.
Probiotics
Probiotics are different in that they contain live organisms, usually specific strains of bacteria that directly add to the population of healthy microbes in your gut.
Like prebiotics, you can take probiotics through both food and supplements. Probably the most common probiotic food is yogurt.
Yogurt is made by fermenting milk with different bacteria, which are left in the final product. Other bacteria-fermented foods, such as sauerkraut, kombucha and kimchi, are also good sources of probiotics.
Probiotic supplements also contain live organisms. A single dose may include a particular strain of microbe or blend of microbes. Like with prebiotic supplements, probiotic supplement companies market products to specific conditions, such as irritable bowel syndrome.
A registered dietitian can help you sort through the food sources of prebiotics and probiotics.
Keep in mind
One thing to understand about supplements is that there are many, many kinds. For instance, one type of bacteria commonly used is lactobacillus. But there are more than 120 species of lactobacillus, and at least a dozen of them are used as probiotics.
What's more, there are several other types of bacteria, each with dozens of species, making for a dizzying variety of available probiotics. And even when you select a kind of bacteria, the amount in the supplement can vary between brands.
When taking a probiotic, research the condition you wish to address and select the probiotic based on that condition. Also, keep in mind that while a probiotic may show promise in treating a condition, it's likely that the research is still in early stages.
While the supplement may have improved a condition for a few people in a very limited circumstance, it may not work as well in real-world settings. As always, when considering taking a supplement, talk to your doctor first.
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Feb. 27, 2021
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