Prebiotics vs. Probiotics: What’s the Difference?

And why it’s important to trust your gut
probiotics and probiotics and their effects

While we think of bacteria as invisible villains, your body is actually teeming with bacteria heroes.

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The gut bacteria (what scientists call gut microbiota) that live in your gastrointestinal tract are magical creatures. They help:

  • Break down and digest food.
  • Communicate with your immune system.
  • Keep inflammation at bay.

Can trendy probiotics and prebiotics keep gut health in tip-top shape? Gail Cresci, PhD, RD, an expert on the gut microbiome, offers her insights into the role pre- and probiotics may play in gut health.

Gut bacteria: The BFFs you never knew you had

“In human intestines, there are many strains of two main species of friendly bacteria, Lactobacillus and Bifidobacterium,” Dr. Cresci says. Probiotics and prebiotics both help those friendly bacteria, but in different ways:


These are live microorganisms isolated from humans and then cultured in a lab to be used as a supplement. When we ingest them (whether in food or supplement form), they survive in the gut and provide benefits to us like the good bacteria that we naturally have.


This is a food source for the friendly bacteria in your intestinal tract. Our digestive system can’t break down prebiotics, so they survive the journey through the digestive tract. They eventually reach the part of the colon where the friendly bacteria hang out. The bacteria have the chops to break down the prebiotics into nutrition that helps them grow and thrive.

Gut check — do you have enough friendly gut bacteria?

In a healthy state, you can trust your gut to do all the right things for you. Since you already have a good composition of friendly bacteria, you won’t need pre- or probiotics.

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“Americans, unfortunately, don’t always live in a healthy state,” Dr. Cresci notes. “People don’t eat the 25 to 35 grams of fiber that the gut bacteria need to survive and replicate.”

For some people, it may not be a lack of fiber, but rather a chronic disease that results in not enough friendly bacteria in the GI tract. “Gut dysbiosis refers to the bad state of the friendly intestinal bacteria in people whose condition may negatively affect the blend of good intestinal bacteria,” she says.

Are probiotics the key to a well-stocked gut microbiota?

Whether your diet is out of whack or you live with a chronic disease, a probiotic supplement has the potential to help restore your gut to optimum health. There are supplements commercially available that deliver both Lactobacillus and Bifidobacterium, as well as other probiotic species.

“For most people, taking a probiotic is safe,” says Dr. Cresci. “I recommend people living with a chronic disease or who have a suppressed immune system discuss with their doctor about adding more probiotics to their diet to make sure that taking a probiotic is something they should consider doing.” 

Since probiotic supplements can be hard on your wallet, Dr. Cresci recommends other ways to build your gut army, such as eating fermented foods like:

  • Yogurt that contains added Lactobacillus and Bifidobacterium strains.
  • Kombucha, a fermented tea.
  • Tempeh, fermented soybeans.
  • Sauerkraut, fermented cabbage.

Gut health starts with prebiotics

“You can buy prebiotic supplements, but you don’t need them if you eat the foods that fortify the army of friendly bacteria in your intestines,” Dr. Cresci explains.

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She recommends these microbiota-loving foods:

  • Fiber-rich foods: Fruits, vegetables and whole grains.
  • Potatoes: Ideally, a boiled and cooled potato, since the starch is more resistant to digestion.
  • Bananas: Green, less-ripe bananas are rich in resistant starch.
  • Jerusalem artichokes: A root vegetable rich in the prebiotic inulin.

Synbiotics blend both pre- and probiotics

Dr. Cresci is actively studying synbiotics, which combine a prebiotic and a probiotic.

“A probiotic in a capsule may not survive while sitting on the grocery store shelf or passing through the intestinal tract,” she says. “But when you combine it with its food source, the prebiotic, it has a much better shot at staying viable until it reaches the part of the gut where it will ultimately live.”

Dr. Cresci recommends people get their probiotics and prebiotics from a healthy diet, but if you need to take a supplement, she recommends choosing a:

  • Product that has a seal of approval from testing agencies such as Consumer Reports or Consumer Labs.
  • Probiotic capsule packaged with inulin or other prebiotics.
  • Probiotic in spore form, which can survive on the shelf or in the digestive tract.

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