Prebiotics, probiotics, postbiotics: what are the differences?

To understand what prebiotics, probiotics, and postbiotics are, and their benefits, it is crucial to have some key knowledge about the microbiota. This term refers to the collection of microorganisms living in a specific environment. It's worth noting that there isn't just one, but several microbiotas within the human body, the most densely populated being the gut microbiota. The bacteria, yeasts, and viruses of the microbiotas are organised into complex communities, whose balance is delicate.

These microorganisms play a crucial role in the health and immunity of individuals, particularly in providing our protection against pathogens. Different microbiota also have specific tasks unique to them: the gut microbiota aids in digestion, the skin microbiota contributes to the skin's barrier function, etc. These roles can be compromised in the event of imbalance in microorganism populations. To address this issue, the use of prebiotics, probiotics, and postbiotics can be beneficial.

The probiotics are microorganisms external to the body. According to the definition given by the World Health Organisation (WHO) and the Food and Agriculture Organization of the United Nations (FAO), probiotics are "live microorganisms which, when consumed in adequate amounts, confer a health benefit on the host". Used in both the food and cosmetic industries, probiotics have a widespread therapeutic application. They can notably be used in the treatment of intestinal diseases, neonatal diseases and immune diseases, as well as in reducing blood pressure, slowing down ageing, combating tumours and diseases of the central nervous system.

When taken orally, probiotics enrich the gut microbiota and enhance digestion and nutrient absorption. They also help to strengthen the immune system by restoring the balance of the microbiota. The probiotics found in cosmetics also have a wide range of effects and have antioxidant, photoprotective, firming, hydrating, and whitening properties. The most commonly used probiotics in skin and hair care are the bacteria Lactobacillus.

Due to their numerous benefits, it is estimated that the global probiotics industry is growing at a rate of 15 to 20% per year.

Prebiotics are essentially the food of probiotics. These are non-digestible carbohydrates and fibres selectively used by the gut microbiota. Prebiotics can alter the composition and metabolic activities of the microbiota and must provide health benefits for the host. They notably stimulate the growth of certain gut bacteria to allow them to properly perform their functions on the body. At the skin level, they ensure the balance of the microbiota so that certain microorganisms do not dominate others and lead to the weakening of the skin barrier.

Often associated with probiotics in cosmetics, prebiotics are primarily incorporated into treatments targeting blemishes. Indeed, an imbalance of the skin flora, and more specifically an overgrowth of the bacteria Cutibacterium acnes, is one of the triggering factors of acne. By enabling the rebalancing of the skin's microbiota, prebiotics combat the source of spots. They can also be used in products intended for people suffering from rosacea or eczema, as these skin conditions can sometimes be linked to an imbalance of the microbiota.

The ISAPP (International Scientific Association for Probiotics and Prebiotics) defines postbiotics as "preparations of inanimate microorganisms and/or their components that confer a health benefit to the host". In other words, it is the result of the fermentation of prebiotics by probiotics. These can be peptides, organic acids, polysaccharides, enzymes or even proteins.

Less well-known than prebiotics and probiotics, postbiotics nonetheless have positive effects on the body. They are notably capable of modulating the immune response, inhibiting the attachment of certain pathogens and maintaining intestinal barriers. Furthermore, postbiotics have antimicrobial and antioxidant properties that are beneficial not only for the gut microbiota but also for the skin microbiota. Another significant advantage of postbiotics: being non-living microorganisms, they pose no risk of bacterial translocation from the gut to the blood, nor of acquiring antibiotic resistance genes.

• OUWEHAND A. & al. The Production and Delivery of Probiotics: A Review of a Practical Approach. Microorganisms (2019).

• ABENAVOLI L. & al. From Pre- and Probiotics to Post-Biotics: A Narrative Review. International Journal of Environmental Research and Public Health (2022).