Prebiotics versus probiotics: What’s the difference?

Prebiotics and probiotics sound similar, but these nutrients benefit your gut health in different ways.

Here, I answer common prebiotic and probiotic questions I hear as a research dietitian, like the differences between the two, their health benefits and foods where they are found.

How are probiotics and prebiotics different?

Prebiotic foods contain non-digestible components that microorganisms in your gut can break down and use. Think of prebiotics as healthy food for the microorganisms in your gut.

Probiotic foods contain live, active microorganisms that support other gut microorganisms. Think of probiotics as teammates to the microorganisms working to keep your gut healthy.

Where are prebiotics and probiotics found?

Prebiotics and probiotics can be:

• Found in fiber-rich plant foods and foods with live, active cultures
• Added to foods
• Taken as supplements

Here are some examples of prebiotic and probiotic foods.

Prebiotic foods

Prebiotics are found in fiber-rich plant foods, including:

• Fruits: apples, bananas, oranges, watermelon
• Vegetables: asparagus, avocado, beets, broccoli, cabbage, cauliflower, dandelion greens, dried chicory root, fennel, garlic, green beans, Jerusalem artichokes, jicama, leafy greens, leeks, mushrooms, onions, peas, pumpkin, sweet potato
• Beans and grains: barley, beans, bran products, buckwheat, farro, oats, quinoa, rye bread or crackers, whole wheat
• Nuts and seeds: cashews, chia seeds, flax seeds, pistachios, walnuts

Probiotic foods

The easiest way to tell if a food is probiotic? Check its label for the phrase ‘live and active cultures.’

It’s important to read labels because even foods you might assume are probiotic may not be. For example, many – but not all – fermented foods are considered probiotic. That’s because the processing some fermented foods go through can kill live microorganisms, according to the National Institutes of Health (NIH). That's why sometimes probiotics are added to foods after they are processed. The NIH also writes that probiotics are sometimes also added to non-fermented foods.

Some common probiotic foods are:

• Buttermilk
• Cottage cheese
• Kefir
• Yogurt with live, active cultures
• Sauerkraut with live, active cultures
• Tempeh

What are the health benefits of prebiotics and probiotics?

Eating prebiotic and probiotic foods helps increase helpful bacteria in your gut and decrease the amount of pathogenic, or harmful, bacteria.

This can:

• Improve digestion
• Decrease inflammation
• Support your immune system
• Help with bowel regularity
• Reduce gas and bloating
• Help you feel satiated, or full, after eating, which can promote a healthy weight
• Help with nutrient absorption

Another potential benefit of prebiotics and probiotics? Researchers are studying how changes in gut bacteria might benefit anxiety, depression and behavior.

How do I know if I’m getting enough prebiotics and probiotics in my diet?

While some studies have suggested that consuming 3 to 5 grams of prebiotics a day can benefit gut health, there aren’t any official serving recommendations.

So, instead of aiming for a specific serving size, focus on eating a healthy diet that includes fruits, vegetables, whole grains, nuts, seeds and dairy products, such as yogurt with live and active cultures. This will ensure you get a good balance of prebiotic and probiotic foods in your diet, which will help the good bacteria in your gut thrive.

Another tip? Eat a variety of prebiotic and probiotic foods. Different prebiotic foods support different types of microorganisms in your gut. Likewise, different probiotic foods have different strains of bacteria. That means only getting probiotics from a certain type of Greek yogurt with live, active cultures means you are only consuming a few strains of helpful bacteria out of the millions and millions out there.

Should I take a prebiotic or probiotic supplement?

If you are concerned you aren’t getting enough prebiotics and probiotics through diet alone, you may be wondering whether a prebiotic or probiotic supplement is right for you.

It's natural to want a quick way to get all of the health benefits of prebiotics and probiotics. While it may seem easier to get prebiotics and probiotics from one supplement versus a range of foods, I still recommend whole foods over supplements. That’s because supplements don't provide all the vitamins and minerals that our bodies need. Plus, the Food and Drug Administration (FDA) regulates supplements differently than food and medication. This makes it hard to know the quality of a supplement or even how much prebiotic or probiotic it contains.

Another important note? You can’t supplement your way out of an unhealthy diet. Taking prebiotic and probiotic supplements won’t override your existing eating patterns.

The best way to decide if a prebiotic or probiotic supplement is right for you is by speaking with your health care provider. They can make sure it is safe for you to take a supplement and that it won’t interact with any other medications you take.

What should I know before adding more prebiotics and probiotics to my diet?

Ready to add more prebiotic and probiotic foods to your diet? Start slowly.

Everybody processes food differently. Eating more prebiotics and probiotic foods means taking in a lot of fiber, which can lead to gastrointestinal discomfort for some people. Start by adding small amounts of prebiotic and probiotic foods to your diet to give your body time to adjust and minimize gastrointestinal discomfort like gas, bloating or constipation.

Make note of how your body feels after adding prebiotic and probiotic foods. If you are responding well, you can gradually increase your serving size.

While it’s always good to make healthy changes to your diet, first check in with a doctor or registered dietitian. They can help you determine if you have any underlying health issues, as well as provide tips for how to safely add more prebiotics and probiotics to your diet.

Are prebiotics and probiotics safe for cancer patients?

Here’s what to know if you are a cancer patient thinking about adding more prebiotics and probiotics to your diet.

Prebiotic and probiotic foods

Prebiotic foods include fruits, vegetables and whole grains. These food groups are healthy choices, regardless of if you have cancer or not. However, drastically changing your diet to include more fiber can cause gastrointestinal side effects.

Probiotic foods are a bit more iffy for people on cancer treatment. In addition to possible gastrointestinal side effects, these foods may impact treatment or medication.

Prebiotic and probiotic supplements

Cancer treatments such as radiation and chemotherapy can kill the good bacteria in your gut. However, it isn't recommended to replenish those good bacteria using prebiotic and probiotic supplements. This is because these supplements can hurt your gut microbiome and may interact with treatment or medication.

The bottom line for adding prebiotic or probiotic foods or supplements during cancer treatment? Speak to your care team first to make sure it is safe.

How can I tell if prebiotics and probiotics are working?

Your body gets used to what you feed it. Someone who is used to eating more fast food and less fruits and vegetables who starts eating prebiotic and probiotic foods may notice gastrointestinal changes and perhaps some initial weight loss as their body adjusts to a healthier diet.

But does that mean the prebiotics and probiotics are changing your gut microbiome? It’s hard to tell without taking a stool sample. Most likely, many of us won’t be sending our stool to a lab for analysis. Nor is there a way to know if prebiotics and probiotics are working based on how your stool looks. Plus, other diet or exercise changes may be causing the outcomes you are seeing.

Instead, focus on consistency. It's not about eating fruits and vegetables and whole grains on occasion; it’s about eating them on a regular basis. It doesn't take long to change the gut microbiome. So, if your diet is consistent and you’re getting enough fiber, you’re probably changing your gut microbiome.

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