What they are, and why they are important
By UNIVERSITY OF MELBOURNE
When it comes to our health, many of us are familiar with prebiotics and probiotics, along with their significant advantages for our digestive health, even if distinguishing between them can be challenging. But what about postbiotics?
For a brief overview, probiotics are living
microorganisms, often referred to as ‘good bacteria’, that we ingest through
our food to foster a healthy gut microbiota – the vast collection of trillions
of bacteria typically residing in our intestines.
Probiotics such as Lactobacillus and Bifidobacterium,
also known as lactic acid bacteria, are found in
fermented foods including yogurt, sauerkraut, some cheeses, and certain
fermented beverages, as well as dietary supplements.
Prebiotics are what the probiotics feed on,
primarily the undigestible plant materials in our diet including fibers that
only can be used by the probiotics and gut microbiota.
Fruits including bananas and apples,
vegetables such as Jerusalem artichokes, leek and asparagus, onions, garlic,
and also certain cereals, nuts, and legumes are rich in prebiotic compounds.
Certain combinations of probiotics and
prebiotics can be used together to boost the beneficial effects of probiotics
when consumed, and these are known as synbiotics.
So what are postbiotics?
As their name may suggest, postbiotics are what are generated after the digestion of certain foods. They are the breakdown products or ‘metabolites’ following the digestion of prebiotics and fiber-rich compounds by probiotics and our gut’s resident microbiota.
The colon, the lower part of our digestive
system is where many postbiotics are produced, as the microbiota and food we
eat go through a phase called colonic fermentation in the colon.
One of the important things that happen
during colonic fermentation is the breakdown of non-digestible prebiotic and
fiber substances in our diet by gut microbiota. This produces beneficial
compounds for our health like short-chain fatty acids, certain vitamins
(Vitamin B and K), amino acids, and antimicrobial peptides
that prevent the growth and activities of harmful bacteria.
Even some carbohydrate substrates known as
secreted polysaccharides and exopolysaccharides produced by these bacteria
provide various beneficial effects, and so are considered postbiotics.
But because the concept of postbiotics is
relatively new, the process of defining them is still a work in progress. In
our article Nature Reviews Gastroenterology &
Hepatology, we discuss the definition of probiotics and their
importance in enabling consumers to understand which products have
health-promoting properties.
Benefits of postbiotics
Generally, postbiotics can provide us with
similar benefits to that of probiotics and prebiotics.
But the beauty of postbiotics is they can
provide these benefits even without any side effects that probiotics and
prebiotics may have. For example, some people might experience discomfort
because of a temporary increase in gas and bloating after intake of probiotics
and prebiotics.
So you can take postbiotics as supplements if
you cannot tolerate them or you do not like consuming probiotics and
prebiotics.
One of the well-known benefits of postbiotics
is their ability to shift our gut microbiome toward a healthy composition.
Research has shown that beneficial postbiotic compounds can support the growth,
activities, and functions of probiotics and gut microbiota.
It is more like a boosting effect, so that
our gut microbiota, which plays a crucial role in our overall health, can fight
against pathogenic microorganisms like Salmonella in our body. As we know
healthy gut microbiota keep us healthy as they can positively influence our
overall health.
Postbiotics can also stimulate our immune system as well. For
example, exopolysaccharides produced by Lactobacillus delbrueckii ssp. bulgaricus, one of the starter culture bacteria
used to produce yogurt, have the ability to enhance the activity of the body’s
natural killer cells.
Similar
positive effects on the immune system were shown in a
recent study where researchers used exopolysaccharides produced
by Lactiplantibacillus plantarum isolated from human
breast milk.
Postbiotic short-chain fatty acids produced
by the digestion of fiber-rich plant foods can also lower the risk of colon cancer. They are
considered cancer-protective metabolites. Some positive effects of postbiotics on breast
cancer patients have also been shown.
It is still early days for postbiotics
research, with most of these studies being cellular-based lab experiments or
performed on animals. However, their applications in humans are promising.
Are dead probiotics useful?
For beneficial probiotic effects, they must
be live when consumed and travel through our gut. But recent research shows
that even if you completely remove the probiotic cells from its growth medium,
for example, the food source the probiotics are grown in, the cell-free source can still produce some positive effects including
boosting the immune system.
This appears to be because some postbiotics
produced by these probiotics when they are in food remain even if you remove
all living probiotics. For example, some exopolysaccharides and vitamins remain
active and do not degrade in the food before we consume them.
Some dead probiotics and their cell
components have also been shown to provide beneficial effects. But much more
research needs to be done in this area.
How to harness the benefits of postbiotics
As the field of probiotics is still growing,
there will be a lot more to discover in the coming years.
For now, the best thing we can do for gut
health is to consume probiotic-containing foods like yogurt and sauerkraut
because they contain both the postbiotics that have been produced during
processing and storage as well as the living probiotics, which will continue to
release more postbiotics in the gut.
Including prebiotic-rich plant foods in the
diet will then add to these health benefits, providing the food for probiotics
as the first step towards a healthy gut microbiome.
Reference: “Postbiotics — when simplification
fails to clarify” by José Eleazar Aguilar-Toalá, Stefania Arioli, Pradip
Behare, Clara Belzer, Roberto Berni Canani, Jean-Marc Chatel, Enza D’Auria,
Mônica Queiroz de Freitas, Eran Elinav, Erick Almeida Esmerino, Hugo S. García,
Adriano Gomes da Cruz, Aarón F. González-Córdova, Simone Guglielmetti, Jonas de
Toledo Guimarães, Adrián Hernández-Mendoza, Philippe Langella, Andrea M.
Liceaga, Marciane Magnani, Rebeca Martin, Mohammad Tamrin Mohamad Lal, Diego
Mora, Mehran Moradi, Lorenzo Morelli, Fabio Mosca, Filomena Nazzaro, Tatiana
Colombo Pimentel, Chao Ran, Chaminda Senaka Ranadheera, Maria Rescigno, Azucena
Salas, Anderson S. Sant’Ana, Katia Sivieri, Harry Sokol, Valentina Taverniti,
Belinda Vallejo-Cordoba, Jaroslav Zelenka and Zhigang Zhou, 23 September
2021, Nature Reviews Gastroenterology & Hepatology.
DOI: 10.1038/s41575-021-00521-6