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May 19, 2022
By: Olivia Peláez, MS, FMCHC

The old adage “you are what you eat” may be more accurately stated as “you are what you feed the trillions of microbes that make up your microbiome.” Our microbiome is made up of trillions—yes, trillions with a T—of microbes, primarily bacteria, that create a mini ecosystem that has a major impact on our overall health.

Similar to our DNA, the composition of our gut microbiome is unique to each of us. It is impacted by a variety of factors including diet, lifestyle, stress, medication use, and our environment. The moment we are born, our gut microbiome begins to develop. Thanks to our mothers, our gastrointestinal microbiota is initially inoculated during birth, either via vaginal delivery or cesarean section, and is further enhanced through the consumption of breastmilk. As we grow, so does the dynamic microbial diversity and complexity of our microbiome. Unfortunately, as a result of a variety of lifestyle factors, an imbalance between “good” and “bad” bacteria can lead to dysbiosis.

Improving and optimizing health through modulation of the microbiome is not only an emerging area of scientific research but should also be central to a comprehensive, holistic approach to wellness. Cue prebiotics and probiotics. Both play an important role in supporting a healthy gut microbiome which, in turn, can have positive downstream effects on many aspects of health including immune, digestion and cognition.

I’m here to break down each of these for you and provide an understanding of the important role of each and how they work together.


The word “prebiotic” is derived from two Latin words: prae meaning “before” and bioticus meaning “pertaining to life.” Thus, it makes sense that prebiotics play an important role in supporting the life of certain bacteria in our microbiome.

The International Scientific Association for Probiotics and Prebiotics defines a prebiotic as a “nondigestible food ingredient (think: certain fibers) that beneficially affects the host by selectively stimulating the growth and/or activity of one or a limited number of bacteria in the colon.” For food ingredients to be classified as prebiotics, they must:

  1. Neither be digested or absorbed in the stomach or small intestines—their goal is to make it to the colon
  2. Act as a selective food source for one or a limited number of potentially beneficial commensal bacteria in the large intestine (i.e. Bifidobacteria and Lactobacillus)
  3. Change the colonic microflora towards a healthier composition
  4. Induce changes that improve the health of the individual consuming them

Their function or purpose is to strategically support the growth of beneficial bacteria in the colon and they can do this in a variety of ways. One way is by acting as food or fertilizer for the “good bacteria” to promote their growth. Another way is by competitively taking up space from harmful bacteria, essentially forcing them out.

The benefits of prebiotics on gut health are robust and ever-evolving. They include:

  • Enhanced growth of beneficial bacteria (i.e. Bifidobacteria and Lactoabacillus) which can help to correct dysbiosis
  • Improved digestive function and regulate bowels
  • Improved immune response
  • Enhanced mineral absorption
  • Improved bioavailability of phytoestrogens (which may be especially beneficial to women after antibiotic treatment)

Research is emerging to demonstrate that prebiotics may be beneficial in the treatment of irritable bowel syndrome (IBS), atopic eczema, and even be protective against colon cancer.

The most commonly-studied prebiotics are the soluble fibers inulin, fructooligosaccharides (FOS), and galactooligosaccharides (GOS). Many plant-foods are good sources of prebiotic fibers. However, keep in mind that most prebiotics are dietary fibers, but not all dietary fibers are prebiotics.


Looking for ways to boost your intake of prebiotic-rich foods? Try incorporating some of the following prebiotic-rich foods:

  • Asparagus
  • Avocado
  • Cabbage
  • Garlic
  • Banana
  • Jerusalem artichokes
  • Onions, leeks, scallions
  • Apples
  • Oats


Probiotic, a word derived from Latin, means “for life.”

The National Institutes of Health (NIH) define probiotics as live microorganisms, or “good bacteria,” that when consumed in adequate amounts have a beneficial effect on the individual taking them.

Key characteristics of a good probiotics include:

  • The ability to survive gastric acid and bile salt (i.e. survive through the harsh environment of the upper GIT)
  • An ability to adhere to the intestinal lining and colonize the GIT
  • Have clinically documented and validated health benefits

Probiotics work in the GIT in a multitude of ways. Similar to prebiotics, probiotics also compete with potentially ‘bad’ microbes in the GIT for the limited space that is available. Probiotics are also able to interact with immune cells to reduce intestinal inflammation and visceral hypersensitivity which are believed to be contributing factors of IBS and other functional GI disorders.1 Additionally, probiotics can directly strengthen the intestinal barrier and play an important role in treating leaky gut syndrome.

probiotics vs prebiotics

However, the tricky thing with probiotics is that these beneficial bacteria are not able to take up a permanent home in the gastrointestinal tract (GIT) and only survive weeks or even days, depending on the strain. Instead, research shows that in order for them to have a beneficial impact, they should be consumed on a regular and consistent basis—think: daily.

Fermented foods like yogurt, kefir, sauerkraut, kimchi, and pickled vegetables are considered probiotic foods. In addition to probiotic foods, supplements are a great way to nourish the gut with healthy bacteria. When choosing a high-quality probiotic, look for a live culture with at least 1 billion colony forming units (CFU) and containing the genus Lactobacillus, Bifidobacterium, or Saccharomyces boulardii, which are some of the most researched probiotics.


Synbiotics, as the name suggests, are foods or supplements that contain a combination of probiotics and prebiotics in a synergistic blend. While the term “synbiotic” may be fairly new, supplements offering a blend of pre and probiotics have been available for years. When in tandem, research suggests that probiotics are better able to survive the upper GIT and have enhanced implantation in the colon. However, the research is still out on synbiotics. In the meantime, it may be best to consume a high-quality probiotic and a diet rich in prebiotic foods.

1 Mayer EA, Bradesi S, Chang L, Spiegel BM, Bueller JA, Naliboff BD. Functional GI disorders: from animal models to drug development. Gut 2008; 57: 384–404.