Prebiotics and probiotics are important factors in maintaining a healthy gut. The health of your gut impacts your digestion, immunity, metabolism, heart health, brain health, and risk of various diseases, therefore it’s important to maintain your gut health. Here is an overview of prebiotics and probiotics as well as foods you can eat to support gut health.  


What is the gut microbiome?

The gut microbiome is made up of the trillions of microorganisms that live in the gastrointestinal tract, mostly in the large intestine. It’s composed of microbes such as bacteria, yeast, fungi, and viruses, although mostly bacteria. The gut microbiome contains both beneficial and potentially harmful bacteria, although the types and amount of bacteria can vary broadly from person to person.


What are probiotics?

Probiotics, which comes from the Greek word that means “for life”, are the beneficial microorganisms that live in the gut.  

Most probiotics are bacteria, although some yeast have also been identified as probiotics. Some of the bacteria that are known probiotics in humans include Lactobacillus acidophilus, Lactobacillus plantarum, Bifidobacterium bifidum, Bifidobacterium infantis, and Streptococcus salivarius

A microbe must meet several criteria to be considered a probiotic:

  • Must have a health benefit (e.g., reduce harmful bacteria in the gut)
  • Must be resistant to stomach acid, bile, and other digestive enzymes
  • Must be able to colonize in the intestines

Some of the health benefits of probiotics are listed below, although not all probiotics produce all of these benefits. Specific strains of probiotics have been linked to specific health outcomes. 

  • Alleviate gastrointestinal disorders such as diarrhea, lactose intolerance, irritable bowel syndrome, ulcerative colitis, and Crohn’s disease by reducing harmful bacteria in the gut. 
  • Prevent infections caused by bacteria on contaminated foods.
  • Synthesize nutrients such as vitamin K and some B vitamins.
  • Probiotics produce short-chain fatty acids (SCFAs) when they ferment indigestible fibers in the colon. SCFAs are a source of nutrients for colon cells and may help reduce inflammatory diseases, boost immune function, and help stabilize blood sugar levels. 


Probiotic foods 

Diet can help increase the number of and diversity of beneficial bacteria in the gut. For a food to be considered a probiotic, it must have a sufficient amount of live strains of beneficial bacteria that survive any food processing. Those live strains of bacteria must have a known positive health effect. 

Many fermented foods contain probiotics.

  • Kimchi
  • Sauerkraut
  • Kefir
  • yogurt with live active cultures
  • Tempeh
  • Kombucha
  • Miso
  • Some pickled vegetables contain probiotics. 

However, all fermented foods are not necessarily probiotic foods. 

Two common probiotics, Lactobacillus and Bifidobacterium, can both be found in yogurt.  Lactobacillus may help alleviate diarrhea and help digest lactose in people with lactose intolerance, while Bifidobacterium may help with symptoms of irritable bowel syndrome. 

You can also get probiotics from dietary supplements and functional foods, which are foods and drinks (e.g., granola bars, protein shakes) that have probiotics added to them. 

Since each strain of probiotics can have different beneficial health effects, you want to consume a variety of probiotics. Therefore, try to incorporate a variety of probiotic foods into your diet. 


What are prebiotics?

Prebiotics are nondigestible carbohydrates that probiotics can ferment and feed off of in the colon. 

Most prebiotic foods are carbohydrates that are high in fiber. Fruits, vegetables, beans, and certain whole grains are generally good sources of prebiotics.

Nondigestible carbohydrates, such as oligosaccharides and fiber, are resistant to being broken down by digestive enzymes therefore they are not absorbed in the small intestine and end up in the colon where they are fermented by bacteria in the gut. Oligosaccharides, resistant starch, fructooligosaccharides, inulin, and pectin are all prebiotic compounds.

Oligosaccharides are nondigestible complex carbohydrates made up of 3 to 10 sugar molecules. Legumes are the primary source of oligosaccharides.

Resistant starch is a form of starch that is not completely broken down by amylase in the digestive tract, therefore it acts like dietary fiber. Oats, legumes, cooked and cooled rice and potatoes, plantains, and green bananas and good sources of resistant starch. 

Fructans are polymers of fructose molecules that can be shorter in length (fructooligosaccharides) or longer in length (inulin). Fructans naturally occur in artichokes, asparagus, leeks, garlic, onions, jícama, barley, and wheat. 

Pectin is a type of soluble fiber that’s found in cell walls of plants to give them structure. Some foods high in pectin are apples, citrus fruits, bananas, cherries, cabbage, potatoes, and beans.  

The fermentation of prebiotics in the colon has several beneficial health effects. When the beneficial bacteria in the colon metabolize prebiotic compounds, they produce short-chain fatty acids that are used by colon cells for energy. Prebiotics can also help stabilize blood glucose levels, lower blood lipid levels, and help prevent constipation and diverticulosis.   

Different prebiotics will stimulate the growth of specific strains of probiotics, so it’s important to consume a variety of foods with prebiotics to promote a diversity of beneficial bacteria in the gut.  


More Basic Nutrition Articles

Basics of a Healthy Metabolism

Nutrition 101: What are Macronutrients?

Nutrition 101: How Your Digestive System Works

Nutrition 101: How to Balance Blood Sugar Levels

How to Meal Prep: The Steps to Start



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