What's The Difference Between a Probiotic and Prebiotic?

Eating foods that promote your gut health is important, since your gut health impacts various other facets of your overall health. Probiotics and prebiotics are two important nutrients for gut health that help gut bacteria that's good for you to flourish.

Probiotics help introduce new beneficial microorganisms to your microbiome, while prebiotics help feed these microorganisms.

Keep reading to learn more about what probiotics and prebiotics are, their benefits and risks, and how to add them to your diet.

What Are Probiotics and Prebiotics? 

Probiotics and prebiotics work together to promote good digestive health, and each has a different role.

Probiotics

Your gut is made up of trillions of bacteria. Probiotics are live microorganisms, similar to or the same as the ones that exist in your gut. They can be found in certain foods or you can purchase them as supplements. There are a variety of species of probiotics. Lactobacillus and Bifidobacterium are the most common.

Prebiotics

Prebiotics help beneficial gut bacteria to grow and thrive. Think of them like food for healthy gut bacteria. Prebiotics are a form of dietary fiber that feed the good bacteria in your gut. However, prebiotics are not the same as fiber. They are both, however, non-digestible by human enzymes. Like probiotics, they can be found in foods or in supplements. Some forms of probiotics produce short-chain fatty acids like butyrate, acetate, and propionate through fermentation.

What Are The Benefits?

One of the best benefits of adding probiotics and prebiotics may be improved health. That’s because gut health impacts so many other aspects of our health. 

Better Gut Health

Of course, the main thing that comes to mind when you think of prebiotics and probiotics is probably gut health, but what does the research say? 

Probiotics may help prevent antibiotic-associated diarrhea, constipation, and Clostridium difficile infection. Probiotics may also help manage symptoms of irritable bowel syndrome (IBS) and maintain or induce remission of ulcerative colitis a type of inflammatory bowel disease (IBD).

That being said, the American Gastroenterology Association does not recommend using probiotics to treat IBS because there is insufficient evidence to support their benefits. Plus, most research reviews are inconclusive because of the wide variations in probiotic strains studied and the mixed results of the studies.

Research demonstrates mixed results for prebiotic use and gut health benefits. Some studies have shown that taking prebiotics doesn’t impact IBS or IBD, while others have found that it improves symptoms of these conditions. 

Meanwhile, some studies have shown that taking both prebiotics and probiotics could protect against the development and progression of colorectal cancer. 

Improved Immune Function

Both prebiotics and probiotics are associated with improved immune health because of the gut’s impact on immune functioning. For example, a prebiotic mixture of oligofructose and inulin—found in foods like onions, bananas, and garlic—has been shown to promote the body’s immune response to influenza and measles vaccines, while galacto-oligosaccharides—found in beans and some dairy products—are associated with a reduced risk of atopic dermatitis (an immune condition) in infants.

Additionally, probiotic supplementation may play a role in preventing upper respiratory tract infections and reducing the length of infection when compared with placebo or no treatment, according to a 2022 Cochrane review.

Better Mental Health

The gut-brain axis is an area of interest for researchers. Existing research has shown that prebiotics and probiotics may improve various mental disorders including anxiety, schizophrenia, Alzheimer’s, depression, autism, and more through various pathways.

One study found that probiotic supplementation reduced measures of stress and improved mental flexibility in older adults. Others have found that probiotics reduce symptoms of mild to moderate depression and reduced anxiety scores in some people.

While more research is necessary to fully understand this connection and determine specific treatment protocols using probiotics and prebiotics for mental conditions, there is potential for these to become treatment options with a low risk of side effects. 

Better Absorption of Certain Micronutrients

Consuming prebiotics, particularly fructans found in foods like wheat, rye, and onions, is associated with improved absorption of calcium, leading to better bone mineral density. Prebiotics may also help with the absorption of magnesium and iron.

Furthermore, a 2021 systematic review examining the effects of probiotics on micronutrient absorption found that taking probiotics was associated with improved status of vitamin B12, calcium, folate, iron, and zinc in healthy individuals.

Which Foods Are Prebiotics?

Most prebiotic foods are oligosaccharide carbohydrates including galacto-oligosaccharides, starch and glucose-derived oligosaccharides, and others. Some examples of prebiotic foods include:

• Asparagus
• Sugar beet
• Garlic
• Chicory 
• Onion
• Jerusalem artichoke 
• Wheat
• Honey
• Banana
• Barley
• Tomato
• Rye
• Beans

Which Foods Are Probiotics?

Probiotics are commonly found in fermented foods since the fermentation process often causes these bacteria to grow. They are also added to certain foods, like yogurt. Here are some good food sources of probiotics:

• Yogurt
• Kefir
• Kimchi
• Kombucha
• Sauerkraut
• Miso

There are also an increasing number of foods with added probiotics, like sparkling beverages or cereals. However, sometimes these products or the ones listed above may not contain legitimate probiotic strains, causing them to degrade before exerting a benefit on the gut. 

Potential Risks and Side Effects

Generally, probiotics are safe to consume with minimal side effects. The most common side effects are minor gastrointestinal symptoms like gas. However, if you are severely ill or immunocompromised, you may need to be more cautious since taking probiotics has been linked with a few cases of severe side effects like bacteremia, fungemia, or infections that lead to severe illness in these populations.

Similar to probiotics, the most common side effects of prebiotics are relatively minor yet uncomfortable gastrointestinal symptoms like diarrhea, bloating, cramping, and gas. A dose of 2.5–10 grams per day of prebiotics has been proposed to strike a balance between too much and too little, both of which can lead to unpleasant gastrointestinal symptoms.

Are They Good For You? 

Most people benefit from regularly consuming prebiotic- and probiotic-rich foods since they promote a healthy gut microbiome. They’re an important part of a well-rounded diet, and they contain other important nutrients like vitamins, minerals, and antioxidants. However, if you are severely ill or immunocompromised, it’s best to speak with your healthcare provider before adding more of these foods to your diet.

Even for the general public, whether or not you should take a prebiotic or probiotic supplement depends on your diet, and any health conditions. For example, for someone who doesn’t like food sources of probiotics or who is on a course of antibiotics, it may be worth trying a probiotic supplement. However, these supplements can be expensive and there’s still a lot left to be learned about them, so splurging on a costly supplement is often unnecessary for those who eat food sources of probiotics and prebiotics.

Since many sources of prebiotics are also sources of fiber, it’s best to increase your intake slowly if you’re not already consuming these foods regularly. Increasing your intake too quickly can lead to uncomfortable digestive symptoms. 

A Quick Review 

Prebiotics and probiotics are helpful for promoting a diverse and thriving gut microbiome. Not only can they promote gut health, they may also improve immune health, mental health, and improve absorption of certain micronutrients.

While more research is necessary to develop specific treatment recommendations using probiotics and prebiotics, food sources can typically be safely incorporate into a varied diet through foods like yogurt, kimchi, onions, bananas, and beans.