1. Increases in Bifidobacteria and Lactobacilli

Both of these families of bacteria have been shown to be beneficial. For example, lactobacilli reduce inflammation in the gut lining, help with the digestion of lactose, alleviate constipation, improve irritable bowel syndrome (IBS) symptoms, and potentially help prevent traveler’s diarrhea.  Bifidobacteria also reduces inflammation and IBS type symptoms.  We don’t how they help specifically but we know that these are key species in our gut and they make short chain fatty acids which are also beneficial to our health. Low amounts of these are associated with various diseases.

2. Production of beneficial metabolites

In particular what is known as short chain fatty acids (SCFA). Acetate, propionate, and butyrate represent 90–95% of all SCFAs produced in the colon. These SCFA are important for the health of the cells in our large intestine and for ensuring the pH in the colon stays stable and in doing so prevents inflammation, IBD and cancers (2)

3. Increases in calcium absorption

We absorb calcium in our colon and studies have shown that an increase in the intake of prebiotics increased the absorption of calcium (due to the fermentation and production of acid from the SCFA). More studies are needed because it seems to be age, dose, and type of prebiotic related as not all study results were positive.  There are some studies that show that prebiotics may also indirectly increase the absorption of magnesium and iron but there is not enough research to substantiate this (3).

4. Decreases in protein fermentation.  When protein is fermented it can create substances that are considered toxic to the body so prebiotics can reduce that effect. 

5. Decreases in pathogenic bacteria populations

Inhibiting pathogens such as E. coli, Salmonella spp, Campylobacter, and other pathogenic bacteria by keeping the environment acidic (pathogenic bacteria don’t like acidic environments), prevent bacteria from fueling themselves, enhance the immune system and encourage the production of substances that kill the bacteria.

6. Decreases in allergy risk by increasing Bifidobacteria and Lactobacilli (low amounts are associated with allergic reactions especially eczema and rhino-conjunctivitis). 

7. Effects on gut barrier permeability – epithelial cells which form a barrier and mucin layer which forms gel like substance (mucus)  that stops pathogenic bacteria or substances crossing the barrier and entering the bloodstream due to ‘leaky gut’. Leaky gut is associated with an inflamed gut.  Specific proteins either open or close ‘tight junctions’, when there is severe inflammation these tight junctions don’t close tightly and allow substances across that shouldn’t be there. SCFA produced by fermentation of prebiotics improves the barrier function, tightens up those tight junctions and decreases inflammation.  

8. Improved immune system defense. A large part of our immune system is found in our gut lining – its an important defense system. Immune cells are influenced by SCFA especially butyrate  – talks to our immune system. Mechanisms aren’t yet fully understood other than there is some form of communication going on. Iimmune responses that start in the gut have the potential to affect immune responses at other mucosal surfaces such as in the respiratory system, the urinary-genital system.

9. Reduces risk of cardiovascular disease (3). 

10. May help to reduce the risk of obesity and diabetes (3)