Natural prebiotics: nourish your gut flora with mushrooms.

The scientific research of recent decades has revolutionized our understanding of the importance of the gut microbiota, demonstrating how this complex ecosystem of bacteria, fungi, viruses, and other microorganisms influences not only digestion but also the immune system, mental health, metabolism, and even the body's inflammatory response. In this context, prebiotics take on a fundamental role as selective modulators of the composition and activity of the microbiota, promoting the growth and activity of beneficial bacterial strains while inhibiting potentially harmful ones.

Fungi, with their extraordinary chemical and structural diversity, represent a particularly interesting source of prebiotics, offering not only classic fibers like beta-glucans but also a variety of unique polysaccharides, chitin, and other bioactive compounds that interact with our microbiota in ways not yet fully understood. This article aims to dissect every aspect of this symbiotic relationship between fungi and gut health, providing readers not only with the theoretical foundations but also concrete data, comparative tables, and references to scientific studies that can guide informed choices in the field of mycology applied to well-being.

Prebiotics: what they are and why they are essential

Before delving into the specifics of fungi as a source of prebiotics, it is essential to fully understand what these substances are and the role they play in maintaining our health. Prebiotics are non-digestible food components that, when they reach the colon, are selectively fermented by specific gut microorganisms, thereby promoting beneficial changes in the composition and/or activity of the microbiota. Unlike probiotics, which are live microorganisms, prebiotics are substances that feed the bacteria already present in our gut, favoring the growth of beneficial ones.

Scientific definition and classification criteria

According to the most accredited scientific definition, proposed by Gibson and Roberfroid in 1995 and subsequently refined, to be classified as a prebiotic, a substance must meet three fundamental criteria: it must resist hydrolysis and absorption in the upper gastrointestinal tract, it must be fermented by the gut microflora, and it must selectively stimulate the growth and/or activity of one or a limited number of gut bacteria beneficial to health. This definition distinguishes prebiotics from other dietary fibers which, although fermentable, do not exert a selective effect on beneficial bacterial strains.

Main categories of prebiotics

The most studied and recognized prebiotics mainly belong to the category of non-digestible carbohydrates, including:

• fructooligosaccharides (FOS)
• galactooligosaccharides (GOS)
• inulin
• resistant starch
• beta-glucans
• xylooligosaccharides (XOS)

Each of these categories presents different structural characteristics that influence their selectivity towards specific bacterial strains, fermentation rate, and the metabolites produced during the process. Beta-glucans, in particular, represent a class of prebiotics of great interest due to their presence in various fungal species and their immunomodulatory as well as prebiotic properties.

Mechanisms of action of prebiotics

Prebiotics exert their beneficial effects through several interdependent mechanisms. The fermentation of prebiotics by the gut microbiota produces short-chain fatty acids (SCFAs), mainly acetate, propionate, and butyrate, which perform numerous crucial functions for gut and systemic health. Butyrate, in particular, represents the main energy source for enterocytes, the cells lining the colon, contributing to the maintenance of the intestinal barrier integrity and reducing the risk of intestinal permeability.

In addition to the production of SCFAs, prebiotics influence the microbiota through other mechanisms, including the modulation of intestinal pH (which creates an unfavorable environment for pathogens), competition for adhesion sites on the intestinal mucosa, and stimulation of the production of bacteriocins, antimicrobial substances produced by beneficial bacteria. These multiple mechanisms explain why an adequate intake of prebiotics is associated with numerous health benefits that go far beyond improving intestinal regularity.

Health benefits documented by research

Scientific literature has accumulated considerable evidence on the benefits of prebiotics for human health. Clinical studies have shown that regular consumption of prebiotics can improve the absorption of minerals like calcium and magnesium, positively modulate the immune response, reduce the risk of gastrointestinal infections, improve symptoms of irritable bowel syndrome, and even positively influence mood and cognitive function through the gut-brain axis.

A particularly significant study published in the British Journal of Nutrition found that prebiotic supplementation can increase calcium absorption in adolescents by 12%, a relevant finding considering the importance of this mineral for bone health during adolescence. Other studies have shown that prebiotics can modulate the production of gut hormones involved in appetite regulation, suggesting a potential role in body weight control.

Dietary sources of prebiotics

Although prebiotics are often associated with specific supplements, numerous plant-based foods are naturally rich in them. Among the most common sources are chicory, garlic, onion, leeks, asparagus, artichokes, unripe bananas, rye, barley, and, as we will explore in this article, various species of edible mushrooms. The variety of dietary sources of prebiotics underscores the importance of a diversified diet to support gut microbiota health.

It is interesting to note that the prebiotic content in foods can vary significantly based on factors such as variety, degree of ripeness, growing conditions, and methods of storage and preparation. Regarding mushrooms, for example, the beta-glucan content can vary not only between different species but also within the same species depending on the growth substrate, the age of the fruiting body, and the cooking method.

Recommended amounts and practical considerations

Although there is no official recommended daily allowance for prebiotics, most studies that have shown significant benefits used doses between 5 and 15 grams per day. It is important to emphasize that excessive consumption of prebiotics, especially in unaccustomed individuals, can cause temporary gastrointestinal discomfort such as bloating, flatulence, and abdominal cramps. For this reason, it is advisable to gradually increase the intake of prebiotics in the diet, allowing the microbiota to adapt progressively.

For the general population, the goal should be to regularly include a variety of prebiotic-rich foods in the diet, rather than focusing on reaching a specific quantity. This approach not only ensures an adequate intake of prebiotics but also provides a wider range of bioactive compounds that can act synergistically to support microbiota health.

Gut microbiota: an ecosystem to preserve

To fully understand the importance of prebiotics, it is necessary to explore the complex ecosystem they nourish: the gut microbiota. This extraordinary collection of microorganisms, which collectively contain a number of genes 150 times greater than the human genome, represents one of the most fascinating frontiers in biomedical research today, with implications ranging from gastroenterology to neurology, from immunology to endocrinology.

Composition and diversity of the gut microbiota

The human gut microbiota is composed of an extremely diverse community of microorganisms, including bacteria, archaea, fungi, viruses, and protozoa. Bacteria represent the most numerous and studied component, with over 1000 different species identified, although each individual typically hosts 150-200 species. The dominant bacterial phyla in the human gut are Firmicutes and Bacteroidetes, which together constitute about 90% of the gut bacterial community, followed by Actinobacteria, Proteobacteria, Verrucomicrobia, and Fusobacteria.

The composition of the gut microbiota is not static, but dynamic and influenced by numerous factors, including host genetics, mode of birth (vaginal or cesarean), feeding in infancy (breast or formula), age, diet, use of antibiotics and other medications, stress, physical exercise, and environment. This plasticity represents both a vulnerability (negative factors can alter the microbiota balance) and an opportunity (interventions like diet can positively modulate its composition).

Essential functions of the gut microbiota

The gut microbiota performs crucial functions for host health, which can be grouped into several categories:

These functions are not isolated, but closely interconnected, creating a complex network of interactions that contributes to the body's homeostasis. The metabolic function, in particular, is of fundamental importance for understanding the role of prebiotics, as it is through the fermentation of these substrates that the microbiota produces beneficial metabolites like short-chain fatty acids.

Dysbiosis and health consequences

When the balance of the gut microbiota is altered, it is referred to as dysbiosis or intestinal dysbiosis. This condition can manifest as a reduction in microbial diversity, a change in the relative composition of different bacterial taxa, or a functional modification of the metabolic activities of the microbiota. Intestinal dysbiosis has been associated with numerous pathological conditions, including inflammatory bowel diseases, irritable bowel syndrome, obesity, type 2 diabetes, allergic and autoimmune diseases, neurological disorders, and even some types of cancer.

One of the most interesting aspects emerging from recent research is the concept of the "gut-brain axis", which describes the bidirectional communication between the central nervous system and the gut microbiota. This axis involves multiple communication pathways, including the vagus nerve, the immune system, the endocrine system, and microbial metabolites. Alterations in the composition of the gut microbiota have been associated with mood disorders, anxiety, depression, and even neurological conditions such as Parkinson's disease and autism.

Strategies to support microbiota health

Given the importance of the gut microbiota for overall health, it is crucial to adopt strategies to preserve its balance and diversity. These strategies include:

• consumption of foods rich in prebiotic fibers
• inclusion of fermented foods containing probiotics
• reduction of unnecessary antibiotic use
• stress management
• regular physical activity
• adequate sleep

Among these strategies, diet is undoubtedly one of the most powerful tools for modulating the gut microbiota. Studies have shown that significant dietary changes can alter the composition of the microbiota in relatively short times, even within 24-48 hours. However, these changes tend to be transient if not sustained over time, emphasizing the importance of consistent eating habits.

Measurement and analysis of the gut microbiota

With the advent of next-generation sequencing technologies, it has become possible to analyze the composition of the gut microbiota with an unprecedented level of detail. 16S rRNA gene sequencing techniques allow for the identification of different bacterial taxa present in a fecal sample, while shotgun metagenomic sequencing provides information not only on the taxonomic composition but also on the functional potential of the microbiota.

These techniques have revealed that there is a human "core microbiome", consisting of a set of bacterial species shared by most individuals, in addition to a variable component that contributes to the individuality of each person's microbiota. Microbiota diversity, understood as species richness and uniformity of their distribution, is generally considered a marker of health, while reduced diversity has been associated with various pathological conditions.

Prebiotics: the gut microbiota's favorite food

Through this in-depth examination of the role of fungi as a source of natural prebiotics, it becomes clear that these extraordinary life forms represent not only a nutritious and versatile food but also a powerful tool to support the health of the gut microbiota and, consequently, overall well-being. The beta-glucans, chitin, and other polysaccharides present in mushrooms offer a unique structural complexity that translates into selective prebiotic effects and multifactorial benefits.

Scientific research continues to reveal new aspects of this symbiotic relationship between fungi and human health, opening exciting perspectives for the use of fungi not only in the food sector but also in the prevention and therapeutic support of various conditions related to intestinal dysbiosis. However, it is important to emphasize that the benefits of fungi as a source of prebiotics fit into a broader context of healthy lifestyles and a varied and balanced diet.

For mycologists, mushroom growers, and all mushroom enthusiasts, this knowledge represents a further reason to deepen the study and valorization of this fascinating kingdom, promoting not only the conservation of fungal biodiversity but also a greater awareness of the potential of fungi as a resource for human health. The path of research is still long, but the results obtained so far are promising for the future of mycology applied to well-being.