The different ways that prebiotics and fiber affect the gut microbiota

Fiber is a key overlooked nutrient in the diets of many. Although some fiber cannot be digested by humans, it can be broken down by the microbes in our gut – a community of bacteria called the gut microbiota. Like fiber, prebiotics also act as food for beneficial microbes in the gut, and many current prebiotics are actually considered to be a form of soluble dietary fiber. The similarities between fiber and prebiotics often lead to confusion on how to differentiate the two. Luckily, this infographic from the International Scientific Association for Probiotics and Prebiotics (ISAPP)  offers a helpful comparison between prebiotics and fiber while describing the extent to which each affects health and the gut microbiota.

Most fiber is non-digestible carbohydrate derived from plants. For example, apples, black beans, and broccoli are all excellent sources of fiber. Beyond promoting regular bowel movements, adequate fiber consumption improves blood levels of lipids and glucose, while keeping us fuller for longer. Some fiber even has a low to moderate effect on our gut microbiota.

Prebiotics are also readily present in foods such as vegetables and whole grains, and are associated with many health benefits. Prebiotics have been shown to promote gut health, may modulate the immune system, regulate bowel movements, and may be beneficial for disorders such as irritable bowel syndrome. Some of the effects are mediated by short chain fatty acids. Compared to fiber, prebiotics have a much more powerful effect on health and the gut microbiota. A new recently revised definition of the term prebiotic highlights that prebiotic substances may also have beneficial effects beyond the gut by targeting microbes outside of the colon.

For more information on the differences between prebiotics and fiber, take a look at the infographic here.

Megan Mouw
Megan Mouw
Megan Mouw holds a Bachelor of Science in microbiology from McGill University (Canada). Driven by her experiences at UCSF medical center in San Francisco, Megan is passionate about the role that the gut microbiota plays in maintaining health and wellness. She is currently perusing graduate studies in Microbiology and Environmental Toxicology at the University of California Santa Cruz and hopes to share her love of science through writing.