Prebiotics vs. Probiotics: What’s the Difference?

You’ve probably heard of prebiotics and probiotics. And it’s OK if you’ve mixed them up (or thought they were the same thing) at one point or another. But if you’re looking to improve your gut health, it’s worth understanding the difference.

“In human intestines, there are many strains of two main genera of friendly bacteria, Lactobacillus and Bifidobacterium,” says dietitian and microbiome expert Gail Cresci, PhD, RD. Prebiotics serve as a food source to keep gut bacteria doing their job, while probiotics are a type of live, friendly bacteria that benefit your body.

Dr. Cresci shares insight into the role pre- and probiotics may play in your gut health.

What’s the difference between prebiotics and probiotics?

OK, first off, let’s get these two straight. Prebiotics and probiotics help support healthy gut bacteria (which are one type of microbe of what scientists call gut microbiota) that live in your gastrointestinal tract.

Probiotics are friendly bacteria and yeasts that help break down food, communicate with your immune system and keep inflammation at bay. They can be found in fermented foods like yogurt, sauerkraut, kefir and supplements.

Then, there’s prebiotics. Prebiotics are a type of carbohydrate that our bodies are unable to digest. These compounds provide food to the good bacteria in your gut. They can be found in fiber-rich foods like whole grains, asparagus and lentils.

Think of it this way: Probiotics are the seeds you plant in your garden (AKA your gut microbiota) and prebiotics are the fertilizer that helps them grow. When you eat prebiotics, they help the good bacteria grow and do their job better, which keeps your gut and body healthy.

How they work together

There’s an important reason why prebiotics and probiotics work together. As your gut can’t break down prebiotics, they serve as a food source for probiotics to grow. By doing this, prebiotics can help:

• Improve your digestion and metabolism
• Assist in regulating bowel movements
• Improve calcium absorption
• Lower inflammation in your body
• Strengthen your immune system

Prebiotic- and probiotic-rich foods

Before discussing supplements, it’s good to note that you can get plenty of prebiotics and probiotics from your pantry or fridge. Dr. Cresci says that the best way to build your gut army is to adjust your diet accordingly.

If you’re looking to add more probiotics through your diet, try eating more fermented foods like:

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

As for prebiotics, try adding the following to your diet:

• Fiber-rich foods: Fruits, vegetables and whole grains
• Potatoes: Ideally, a boiled and cooled potato, as the starch is more resistant to digestion
• Bananas: Green, less-ripe bananas are rich in resistant starch (a prebiotic)
• Jerusalem artichokes: A root vegetable rich in the prebiotic inulin
• Legumes, beans and peas: These contain a large amount of dietary fiber and act as a good food source for good bacteria in your gut

Do I need to take a prebiotic or probiotic supplement?

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

“Americans, unfortunately, don’t always live in a healthy state,” Dr. Cresci clarifies. “People don’t eat the 25 to 35 grams of fiber 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 their gastrointestinal (GI) tract. For example, gut dysbiosis happens when the bacteria in your gut (your intestines) are out of balance.

When the “good” bacteria keep the “bad” ones in check, your gut stays healthy. But if the bad bacteria take over or there aren’t enough good ones, problems can happen, Dr. Cresci points out.

“For most people, taking a probiotic is safe,” she says. “If you live with chronic disease or a weakened immune system, talk to your doctor/provider/dietitian about the best way to add more probiotics to your diet.”

The same goes for prebiotics. “You can buy prebiotic supplements, too, but you don’t need them if you eat the foods that fortify the army of friendly bacteria in your intestines,” she adds.

“A probiotic in a capsule may not survive while sitting on the grocery store shelf or passing through your intestinal tract,” Dr. Cresci continues. “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 your gut where it will ultimately live.”

Dr. Cresci recommends people get their prebiotics and probiotics 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 (for example, Bacillus coagulans, Bacillus subtilis), which can survive on the shelf or in the digestive tract

Key takeaway

If you’re not sure if your gut needs more prebiotics, probiotics or both, talk to a healthcare provider to learn more. A more varied, colorful diet may be the key. In some cases, your provider may recommend a supplement.