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What are synbiotics?

If the word “synbiotics” rings a bell is probably because it sounds like prebiotics and probiotics. All these terms relate to the gut microbiome in ways we will explore to answer the question: what are synbiotics?

The microorganisms that populate our gastrointestinal system, or gut microbiome, has been the focus of much research in the past several decades. It is now known that the gut microbiome is involved in immune function, digestion, gut integrity and production of vitamins, among other important functions (1, 2).


Probiotics are live non-pathogenic microorganisms that can confer health benefits when taken in appropriate doses (1, 3, 4).

Probiotics can act on the gut microbiome can induce physiological and metabolic changes in the host (4).


Prebiotics are substances that are not digested by the upper gastrointestinal tract and become food for beneficial gut bacteria. The end result is health benefits for the host (1, 3).

Prebiotic substances include some or non-absorbable sugars, fibre such as inulin, oligosaccharides and sugar alcohols (1), and potentially polyunsaturated fatty acids (PUFAs) and polyphenols (4, 6). Natural prebiotics usually come from seeds and roots of some plants such as chicory, onions, garlic, artichokes, asparagus, barley, rye, soy beans, chickpeas and lupins. Interestingly, synthetic oligosaccharides made by putting disaccharides together, seem to have better results and fewer side effects than natural ones (1).

What are synbiotics?

Synbiotics are mixtures of one or more probiotics with one or more prebiotics in order to improve the survival of the probiotics in the acidic gastric environment (1, 5). Think about synbiotics as good gut bacteria coming along with their lunchboxes. This combination is thought to be synergistic, which means that the total effect is greater than the sum of the parts.

Health benefits of synbiotics

Although there is not a lot of evidence supporting the use of synbiotics, the current literature suggests that they may:

  • stimulate the immune system (1)
  • improve the absorption or bioavailability of nutrients such as calcium and iron (1)
  • modulate the composition and balance of the intestinal flora (1, 5) and microbial metabolite production (5)
  • improve constipation (1, 5) and diarrhoea (1)
  • reduce intestinal permeability (1)
  • lower blood sugar levels (1, 5)
  • reduce blood cholesterol levels (1)
  • increase resistance against pathogens, which may prevent and reduce postoperative infections (1, 5)
  • improve symptoms, bowel habits and inflammatory markers in patients with irritable bowel syndrome (IBS) (6)
  • help restore the intestinal mucosa in patients with ulcerative colitis by increasing short-chain fatty acids which are fuel for colonic cells (2)
  • reduce inflammation in patients with colorectal cancer (4)
  • inhibit cell growth in colorectal cancer (3)
  • improve infant health by supporting normal growth in infants with cow’s milk allergy, preventing symptoms in infants with atopic dermatitis and supporting gut health in infants born by C-section (5)

Cons of synbiotics

The dosage of both the probiotic and prebiotic part of a synbiotic product needs to be right in order to ensure the survival of enough colony forming units (CFU). Regarding the prebiotic portion, too high of a dose (e.g. 14g/day for inulin) can cause gastrointestinal discomfort (1).

Probiotic use can lead to death of pathogenic bacteria and a subsequent release of toxins that can cause detrimental side effects (1).

Summary and recommendations

The use of synergistic mixtures of probiotics and prebiotics, known as synbiotics, can be used to prevent and treat a variety of health conditions. However, current evidence is not entirely conclusive, so it is best to consult a gut health practitioner experienced in this topic before trying a supplement.


  1. Flesch AG, Poziomyck AK, Damin DC. The therapeutic use of symbiotics. Arquivos brasileiros de cirurgia digestiva : ABCD = Brazilian archives of digestive surgery. 2014;27(3):206-9.
  2. Peña AS. [Intestinal flora, probiotics, prebiotics, symbiotics and novel foods]. Revista espanola de enfermedades digestivas : organo oficial de la Sociedad Espanola de Patologia Digestiva. 2007;99(11):653-8.
  3. Abreu-Abreu AT. [Prebiotics, probiotics and symbiotics]. Revista de gastroenterologia de Mexico. 2012;77 Suppl 1:26-8.
  4. Fong W, Li Q, Yu J. Gut microbiota modulation: a novel strategy for prevention and treatment of colorectal cancer. Oncogene. 2020;39(26):4925-43.
  5. Wegh CAM, Geerlings SY, Knol J, Roeselers G, Belzer C. Postbiotics and Their Potential Applications in Early Life Nutrition and Beyond. Int J Mol Sci. 2019;20(19).
  6. Gracie DJ, Ford AC. Symbiotics in irritable bowel syndrome–better than probiotics alone? Current opinion in clinical nutrition and metabolic care. 2015;18(5):485-9.

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