Prebiotics: types and benefits

The world of probiotics is continually evolving as novel research makes new applications available to the public. However, other concepts have been around for quite some time, like that of prebiotics. Prebiotics are basically food for your digestive bacteria, they are not digested or absorbed by your body, and the reason they are consumed is to increase the activity of one or a group of healthy bacteria in your gut. This increase is usually measured by a prebiotic index, which is a number that represents the expected increase of bifidobacteria in the gut after consuming the product daily.

Therefore, prebiotics are not a myth, they are based on scientific research, and they must fulfill three basic conditions to be considered as such: (1) they are non-digestible, which means that your gastric juice and enzymes can’t break them down, and it can’t be absorbed into your bloodstream; (2) they are fermented by the intestinal microbiota, because they are the ones capable of using these as a source of nutrients; and (3) they stimulate the growth and activity of specific bacterial strains in your gut.

Types of prebiotics
Depending on the primary source, we can break down prebiotics into two different categories: fructans and non-fructan prebiotics.

Fructan prebiotics: These are oligosaccharides typically found in bananas, onions, garlic and whole foods. They are made up of fructose residues, but in the food industry, they can be produced from sucrose as well.

Non-fructan prebiotics: Also called resistant starch, it is a type of starch that cannot be processed and absorbed by our organism. They are usually found in raw potatoes and some kinds of bread and cereals.

These two categories have something in common: since they are not digestible material, they cause an osmotic effect just the same as fiber does. So, prebiotics behaves exactly like fiber (and may be counted as fiber content in foods) until arriving at their final destination, where our intestinal bacteria ferment them.

How to use and get real benefits from prebiotics?
Prebiotics haave a variety of applications in the medical field. They can be used as fiber, increasing fecal mass and reducing constipation. Some studies have found that their fermentation in the colon may protect the area against colon cancer, and the end-product are short-chain fatty acids. Some of these fatty acids can be absorbed into the bloodstream and serve as nutrients, while others control inflammation in the colon, lower the pH and regulate the healthy growth and differentiation of intestinal cells.

Thus, prebiotics can be prescribed, not only for constipation but also to treat inflammatory bowel diseases because they can regulate the immune response within the gut. Since they increase the activity of commensal bacteria, they can prevent a series of infections in the gastrointestinal tract as well. And some authors also describe it can be used to treat hepatic encephalopathy and to prevent cholesterol gallstones. As such, both the probiotics and prebiotics are still subject to intense investigation, leading to an increased number of applications with little to no side effects.

Gibson, Glenn R., et al. "Dietary modulation of the human colonic microbiota: updating the concept of prebiotics." Nutrition research reviews 17.2 (2004): 259-275.
Roberfroid, Marcel. "Prebiotics: the concept revisited." The Journal of nutrition 137.3 (2007): 830S-837S.
Roberfroid, Marcel B. "Prebiotics and probiotics: are they functional foods?–." The American journal of clinical nutrition 71.6 (2000): 1682S-1687S.
Hill, Colin, et al. "Expert consensus document: The International Scientific Association for Probiotics and Prebiotics consensus statement on the scope and appropriate use of the term probiotic." Nature Reviews Gastroenterology and Hepatology 11.8 (2014): 506.
Roberfroid, M. B. "Prebiotics and synbiotics: concepts and nutritional properties." The British journal of nutrition 80.4 (1998): S197-202.
De Vrese, M., Scherezenmeir, J., 2008. Probiotics, prebiotics, and synbiotics. Adv. Biochem. Eng. Biotechnol. 111, 1–66.
Watson, R. R., & Preedy, V. R. (Eds.). (2015). Probiotics, Prebiotics, and Synbiotics: Bioactive Foods in Health Promotion. Academic Press.