What are prebiotics?

Probiotics, which are microorganisms, should not be confused with prebiotics, which are carbohydrates used by microorganisms to feed and grow.
what are prebiotics

The World Gastroenterology Organization (WGO) defines Prebiotic as "selectively fermented ingredient that results in specific changes in the composition and/or activity of the gastrointestinal microbiota, thereby conferring health benefits to the host".

In other words, prebiotics are components, present in many foods, but that the human being does not have the capacity to digest and, as a consequence, they reach the large intestine in a practically unaltered form where they will act as a nutrient for the beneficial bacteria we have there, favoring their growth and promoting, therefore, a healthy gut microbiota.

Prebiotics are basically compounds of food fiber which, once in the large intestine, are fermented by these good bacteria, mainly those belonging to the Lactobacillus and Bifidobacterium genera. This fermentative process generates a series of beneficial compounds, including short-chain fatty acids and, in particular, butyric acid, an essential compound for the proper functioning of our gastrointestinal system.

For a prebiotic to reach the large intestine practically intact, it must be able to withstand gastric acidity and the digestive enzymes that it will encounter before reaching the large intestine and, in addition, it must not be absorbable at the level of the small intestine.

But in addition to reaching the level of the colon, and doing so intact, it must have the property of acting as a specific substrate for certain microbial strains, so that its presence in the large intestine involves a proliferation of only those indigenous species and as a result results in a beneficial effect for the organism.

This property gives prebiotics an enormous potential to modify or modulate the intestinal microbiota and allows them to be an alternative to probiotics or to be administered together with them, in what is called symbiotics.

Types of Prebiotics

Prebiotics are basically carbohydrates (carbohydrates, sugars or polysaccharides) that are present in many foods.

There are different types of prebiotics, depending on the main sugar molecule that forms them (fructose, galactose, etc.), the total number of molecules, and the type of chemical bond that links them.

The most commonly used prebiotics are:

  • Inulin: It is found in chicory root, artichoke, onion, garlic and asparagus, among other foods.
  • Fructooligosaccharides (FOS): Very similar to Inulin. They are found in onions, garlic, bananas, barley, oats and honey, among other foods.
  • Galactooligosacáridos (GOS): Se encuentran en la leche materna y algunos productos lácteos.
  • Resistant starch: It is obtained after cooling a previously cooked food rich in starch (rice, potato, sweet potato, pasta, lentils, peas or buckwheat). The cooling process modifies the starch structure, converting it into resistant starch, which is the one that acts as a prebiotic.

Benefits of prebiotics

In particular, the benefit depends on the type of prebiotic, as it favors the growth of one or another microbial strain depending on the type of prebiotic and therefore has different effects.

benefits of prebiotics

In general terms, prebiotics have a series of beneficial effects, such as:

  • To promote the growth of Bifidobacteria and Lactobacillus at the colon level.
  • Produce short-chain fatty acids by reducing the pH of the intestinal environment. This creates a hostile environment for the growth of potentially pathogenic species.
  • To promote the absorption of calcium, magnesium and iron.
  • Absorb water as they pass through the intestine, favoring gastrointestinal transit.
  • Increased stool weight
  • They can favor the growth of certain bacteria that give rise to metabolites that favor the growth of other beneficial bacteria.

Prebiotics have been shown to prevent the onset of certain diseases such as irritable bowel syndrome (IBS) or inflammatory bowel disease.

In addition, having a balanced gut microbiota also helps us to have a strong immune system and maintain a healthy living.

Side Effects

Side effects are rare but it is important to note that prebiotics can sometimes present intolerance problems such as flatulence or gas due to the fermentative process that occurs in the intestine. It is essential to adjust the dose well, which can be set at 2-3 intakes/day of 5 g each, but which should be reduced in case of the presence of these symptoms of intolerance.

Differences between Probiotics and Prebiotics

Probiotics and prebiotics are two terms related to gut health, but they have different functions and characteristics.

Probiotics are live microorganisms, usually beneficial bacteria, that are consumed to promote a healthy balance of gut bacteria. They are commonly found in foods like yogurt, kefir, and fermented vegetables, as well as in supplement form. Probiotics help maintain a diverse and balanced gut microbiota, which is important for digestion, immune function, and overall health. They can also help alleviate certain digestive disorders and improve bowel regularity.

On the other hand, prebiotics are a type of dietary fiber that serves as a food source for the beneficial bacteria in the gut. They are non-digestible and reach the large intestine intact, where they are fermented by the gut bacteria. This fermentation process produces short-chain fatty acids, which provide energy to the colon cells and support a healthy gut environment. Prebiotics are naturally found in foods such as garlic, onions, bananas, asparagus, and whole grains. They can also be obtained through prebiotic supplements.

In summary, probiotics are live microorganisms that directly introduce beneficial bacteria into the gut, while prebiotics are non-digestible fibers that promote the growth and activity of beneficial bacteria already present in the gut. In a nutshell, a prebiotic is the food of a probiotic.

Both probiotics and prebiotics play important roles in maintaining a healthy gut and overall well-being.

Eduardo Santos de Paz

Pharmacist - Complutense University - Madrid - Spain
Diploma in Ophthalmic Optics and Optometry - Univ. of Barcelona - Spain.

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