Prebiotics are a form of fiber that fuel the growth of the trillions of beneficial bacteria residing in our gut and the rest of the body ̶ taken either in diet or as supplements ̶ called probiotics. To simplify, the probiotics replenish the friendly bacteria, which are fed by prebiotics. Prebiotics are also referred to as “oligosaccharides,” because they are composed of a non-digestible fiber carbohydrate that carries relatively small amount of simple sugar molecules (oligo means few and sacchar is sugar).
When ingested, prebiotics confer infinite health benefits.
Prebiotics improve Colonic Health
After escaping digestion in the upper GI tract, the oligosaccharides (prebiotics) reach the large intestine unchanged where the bacteria ferment or break them.  This fermentation yields short-chain fatty acids (SCFAs), which have a positive key impact on your health. SCFAs have been linked to reduced risk of inflammatory colon diseases like colitis and inflammatory bowel disease.  More so, SCFAs appear to nourish the lining of the colon and even prevent colon cancer by being absorbed into the colonic cells and promoting the death of the transformed cells. 
SCFAs also enhance the motility of the colon and increase colonic blood flow. They can regulate the fluid and ion transit through the colon lining, thereby playing a role in preventing certain forms of diarrhea. 
What’s more? This major by-product derived from prebiotic fermentation significantly improves the symptoms and quality of life in people with functional bowel disorders like IBS.  In a study published in a European journal, a type of SCFA called butyrate considerably reduced the abdominal sensitivity and the pain score.  Moreover, by stimulating the growth of good bacteria, the prebiotic-derived SCFA can help balance the uneven microbial composition in IBS. 
Prebiotics may benefit Cardiovascular Disease
The prebiotic intake may cut some of the risks of heart disease such as lower the cholesterol levels and help you shed some extra pounds.  The oligosaccharides tend to curb appetite and keep you full for a long time. A study conducted on 48 overweight adults showed a noticeable decline in body weight after prebiotic supplementation.  The reduction in body weight was attributed to the reduced levels of a hunger hormone called ghrelin and raised levels of an appetite-suppressing hormone, namely peptide YY.
Prebiotics can boost the Immune System
The SCFAs produced by prebiotic fermentation may also help stimulate your immune system. The prebiotics are shown to directly interact with and activate the immune cells and therefore stave off respiratory and gut infections. 
Prebiotics can assuage Stress and Anxiety
As we know there is a two-way communication between the gut, its microbiome, and the brain via the gut-brain-microbiome axis. An imbalanced gut microbiome can cause an emotional turmoil. The other way around, psychological disturbances can wreak havoc on your gut microbiome. The following effects of prebiotics may account for their anxiety-easing benefits:
- Reduced cortisol (stress hormone) levels 
- Restoration of the microbiome balance
- Increased expression of a relaxing brain chemical called GABA (gamma-aminobutyric acid)
Prebiotics can regulate Minerals and strengthen the Bones
Prebiotics can augment the uptake of minerals, including calcium, magnesium, and probably iron. A 1-year study conducted on 100 teens taking prebiotics showed a sizeable increase in calcium absorption, which in turn, increased the mineral mass in the bones. 
Prebiotics can help Regulate Blood Sugar levels
Being rich in fiber, prebiotics can help stabilize blood glucose levels. Although controversial, the impacts of prebiotics on blood glucose seem to be favorable, including reduced glucose uptake as well as a drop in blood glucose rise after meals. 
- Tan J, McKenzie C, Potamitis M et al. The role of short-chain fatty acids in health and disease. Advanced Immunology. 2014;121:91-119. doi: 10.1016/B978-0-12-800100-4.00003-9.
- Velázquez OC, Lederer HM, Rombeau JL. Butyrate and the colonocyte. Production, absorption, metabolism, and therapeutic implications. Adv Exp Med Biol. 1997;427:123-34.
- Borycka-Kiciak K, Banasiewicz T, Rydzewska G. Butyric acid – a well-known molecule revisited. Przegla̜d Gastroenterologiczny. 2017;12(2):83-89. doi:10.5114/pg.2017.68342.
- Vanhoutvin SA, Troost FJ, Kilkens TO et al. The effects of butyrate enemas on visceral perception in healthy volunteers. Neurogastroenterol Motil. 2009;21(9):952-e76. doi: 10.1111/j.1365-2982.2009.01324.x.
- Slavin J. Fiber and Prebiotics: Mechanisms and Health Benefits. Nutrients. 2013;5(4):1417-1435. doi:10.3390/nu5041417.
- Parnell JA, Reimer RA. Weight loss during oligofructose supplementation is associated with decreased ghrelin and increased peptide YY in overweight and obese adults. The American journal of clinical nutrition. 2009;89(6):1751-1759. doi:10.3945/ajcn.2009.27465.
- Schmidt K, Cowen PJ, Harmer CJ, Tzortzis G, Errington S, Burnet PWJ. Prebiotic intake reduces the waking cortisol response and alters emotional bias in healthy volunteers. Psychopharmacology. 2015;232(10):1793-1801. doi:10.1007/s00213-014-3810-0.
- Abrams SA, Griffin IJ, Hawthorne KM et al. A combination of prebiotic short- and long-chain inulin-type fructans enhances calcium absorption and bone mineralization in young adolescents. Am J Clin Nutr. 2005;82(2):471-6.