Probiotics and prebiotics: what they are and the natural sources 


Probiotics and prebiotics


For a few years now with increasing awareness, the intestine is called “the second brain”; given its ability to influence not only the first-order biological functions (digestion, waste elimination, hormone release, maintenance of the immune system), but also emotional and psychological ones.
It is easy to deduce that the health of the intestinal microflora is connected with overall health and happiness.
The microorganisms that are part of the intestinal microflora, together with food, gastrointestinal secretions and products of the intestinal wall, constitute that mysterious world called intestinal microecology; understanding very well the role of probiotics and prebiotics is fundamental for our health.

What are probiotics and prebiotics

To avoid any kind of confusion – in fact, the two terms are distinguished only by a vowel – I would like to explain them.
The term probiotic refers to living microorganisms: bacteria, mainly lactic acid bacteria, Lactobacillus, Streptococcus, Bifidobacterium and other minor ones; yeasts, in particular Saccharomyces strains.
The term prebiotic refers to food ingredients that are not digestible by our digestive system and are useful in growing the beneficial microorganisms that populate the intestinal microbiota.

Why we need to take foods rich in probiotics and prebiotics

In the intestinal microbiota we have about 1010 – 1012 living microorganisms per gram, some of which have pathogenic and others beneficial characteristics; as long as we are healthy, we can affirm that this numerous ecosystem lives in perfect balance. When, for various reasons, this incredible harmony receives a blow, our diet assumes an absolute importance to reintegrate the microorganisms deputies to the recolonization of the colon; valid allies then for the healing, restoring the original balance.
But taking large amounts of probiotics without feeding them (the prebiotics), would not bring you a lasting or efficient benefit; hence the importance of the synergy between probiotics and prebiotics.
These “foods” arrive in the colon intact, as the body’s enzymes are not able to digest them; moreover, they cannot be hydrolyzed by gastric acids and bile salts.
In this way, our good probiotics find themselves in front of a nice banquet:
but nothing is free; in order to digest them they must first put in place a fermentation process, which will allow the production of short-chain fatty acids (SCFA: learn more here), lactic acid, butyric acid, propionic acid, peptidoglycan; acids that have beneficial effects for a large number of biological functions.

The characteristics of probiotic microorganisms

A microorganism is probiotic when:

is safe and comes from human origin – i.e. already present in our body;

it has a high resistance to the acid environment – so that it reaches the colon still alive, passing through the gastric juices and bile acids;

possesses the ability to adhere to the intestinal walls – so as to recolonize the intestinal microflora, and not be expelled through the excretions in transit;

demonstrates a defensive activity against pathogenic and cariogenic microorganisms.

Why probiotics are good for you

– One of the most important roles of probiotic microorganisms is to lower the intestinal pH (by generating an acidic environment) creating a hostile environment for the growth of the many pathogenic microorganisms.

– In addition, they reduce the possibility of pathogen growth, as they are their direct competitors for both adhesion sites and nutrients.

– They are critical in the production of certain vitamins and amino acids: probiotics synthesize vitamin K and most of the water-soluble B vitamins, such as biotin (B7), cobalamin (B12), folic acid (B11), nicotinic acid (B3), pantothenic acid (B5), pyridoxine (B6), riboflavin (B2), and thiamine (B1) [1]; and produce D amino acids, such as d-leucine, d-phenylalanine, d-alanine, d-aspartate, d-serine, d-tryptophan etc [2].

– They are useful in anti-inflammatory action, not only in intestinal disorders, but also in cardiopathologies, since they help to reduce LDL cholesterol.

– They improve the absorption of nutrients, in particular calcium and iron

– They act as immunomodulators, by inducing natural immunological processes.

– They stimulate the production of cytokines.

– They can reduce the occurrence of cancerous forms: although this process is not yet clear, scientific studies have shown that the presence of Lactobacillus and Bifidobacterium spp., are able to decrease the levels of carcinogenic enzymes [3,4]

– They may offer therapeutic improvement to women with bacterial vaginosis: most likely by enhancing the presence of lactobacillus in the vaginal microbiota [5].

Which foods contain probiotics naturally

Most fermented foods contain probiotics naturally; however, if heat is applied for their preparation, as in the case of sourdough bread, the probiotics will not survive.

Therefore, the foods listed below should be taken at room temperature.

– Yogurt (much better if homemade with organic milk, see the perfect recipe here).

– Milk kefir or water kefir (discover here how you can make it at home).

– Lacto-fermented vegetables like cucumbers or sauerkraut (read the 3rd point of this article for the recipe) or kimchi.

– Miso, tempeh or soy yogurt.

– Kombucha etc.

What does prebiotic mean

Although human biology has relied on prebiotics for as long as we have existed, it wasn’t until 1995 that Glenn Gibson and Marcel Roberfroid began talking about them.
Prebiotic for a decade was described as: “a non-digestible food ingredient that positively affects the host by selectively stimulating the growth and/or activity of one or a limited number of bacteria in the colon, and thereby improves the health of the host” [6]; effectively electing only oligosaccharides from the carbohydrate group.
Then in 2008, the following definition comes into play: “a selectively fermented ingredient that causes specific changes in the composition and/or activity of the gastrointestinal microbiota thereby conferring one or more health benefits on the host” [7]. Thus eliminating the limit set in the first definition, including several new foods in the list of prebiotics.

The characteristics of prebiotic foods

A food is prebiotic when:

has a high resistance to the acidic environment and human digestive enzymes, so that it reaches the colon still intact, passing through the gastric juices and bile acids;

is fermentable by the intestinal microbiota;

it stimulates the growth and/or activity of intestinal bacteria, so as to improve the health of the host [8].

Which foods are prebiotics

Commonly one would answer “those that contain fiber”; but that would not be quite right, as not all dietary fiber is prebiotic.
Here are the main prebiotics:

fructans, such as FOS (fructo-oligosaccharides) and inulin;

lactulose, GOS (galacto-oligosaccharides) and TOS (trans-galacto-oligosaccharides).

starches, such as resistant starch (RS) (to find out how to increase the content of RS in your food read this article)

– plus, despite not being part of carbohydrates, cocoa flavonols also demonstrate prebiotic characteristics.

In the hard-to-pronounce categories just mentioned, we find common foods such as algae such as laminaria, red and brown seaweed (Osmundea pinnatifida, Ecklonia radiate) and microalgae; artichokes; asparagus; banana; barley; beans; blueberries; chicory; corn; honey; garlic; Jerusalem artichoke; leeks; mushrooms; mother’s milk and cow’s milk; nectarine; onion; peas; pears; psyllium; rye; salsify; soybean; sugar beet; tomato; watermelon and wheat [9].

Possible contraindications

Probiotic microorganisms are found in foods generally recognized as safe (GRAS) for almost all the population.
However in the case of serious autoimmune diseases (HIV, etc..) it is better to avoid them, if not under strict medical control: cases of super-infection have been recorded.
In addition, my advice is to get them from natural sources, although obviously they cannot compete with the high quantities of probiotics synthesized in the laboratory (as supplements): precisely because the latter could be too much for someone, especially for individuals considered at high risk (recently operated, multi-pathological, very old people, etc.) [10].
Therefore, try to take natural probiotics through food, which also has other benefits, and feed them with prebiotics offered by nature, thus obtaining lasting improvements without any risk.

Enjoy your natural probiotics and prebiotics at every meal, and good revolution to all


1) Hill MJ. Intestinal flora and endogenous vitamin synthesis. Eur J Cancer Prev. 1997;6(Suppl 1):S43–S45. DOI: 10.1097/00008469‐199703001‐00009
2) A.D. Radkov, L.A. Moe Bacterial synthesis of d-amino acids Appl. Microbiol. Biotechnol., 98 (2014), pp. 5363-5374, 10.1007/s00253-014-5726-3
3) M. Kumar, A. Kumar, R. Nagpal et al., “Cancer-preventing attributes of probiotics: an update,” International Journal of Food Sciences and Nutrition, vol. 61, no. 5, pp. 473–496, 2010.
4) Kechagia, Maria, et al. “Health benefits of probiotics: a review.” International Scholarly Research Notices 2013 (2013)
5) M. E. Falagas, G. I. Betsi, and S. Athanasiou, “Probiotics for the treatment of women with bacterial vaginosis,” Clinical Microbiology and Infection, vol. 13, no. 7, pp. 657–664, 2007.
6) Dietary modulation of the human colonic microbiota: introducing the concept of prebiotics.
Gibson GR, Roberfroid MB J Nutr. 1995 Jun; 125(6):1401-12.
7) Gibson G.R., Scott K.P., Rastall R.A., Tuohy K.M., Hotchkiss A., Dubert-Ferrandon A., Gareau M., Murphy E.F., Saulnier D., Loh G., et al. Dietary prebiotics: Current status and new definition. Food Sci. Technol. Bull. Funct. Foods. 2010;7:1–19. doi: 10.1616/1476-2137.15880
8) Gibson G.R., Scott K.P., Rastall R.A., Tuohy K.M., Hotchkiss A., Dubert-Ferrandon A., Gareau M., Murphy E.F., Saulnier D., Loh G., et al. Dietary prebiotics: Current status and new definition. Food Sci. Technol. Bull. Funct. Foods. 2010;7:1–19. doi: 10.1616/1476-2137.15880
9) R. Jovanovic-Malinovska, S. Kuzmanova, E. Winkelhausen. Oligosaccharide profile in fruits and vegetables as sources of prebiotics and functional foods. Int J Food Prop, 17 (2014), pp. 949-965
10) Harms Reporting in Randomized Controlled Trials of Interventions Aimed at Modifying Microbiota. A Systematic Review. Aida Bafeta, PhD; Mitsuki Koh, MPH; Carolina Riveros, MSc; and Philippe Ravaud, MD, PhD Ann Intern Med. 2018;169:240-247. doi:10.7326/M18-0343


You might also like:

If you consider my work important, your support is crucial:
a small donation will carry on the Revolution!
Thank you

Probiotics and prebiotics: what they are and the natural sources
Article Name
Probiotics and prebiotics: what they are and the natural sources
" A Sound Mind in a Sound Gut". Let's discover the importance of probiotics and prebiotics to stay physically and mentally healthy
Publisher Name
CHE Food Revolution
Publisher Logo