Probiotics and Prebiotics: The Duo That Cares for Your Inner Universe
For decades, medical science treated the gut as a simple digestive tube. Today we know it's an intelligent organ,
The Intestinal microbiota it's one of the most searched topics on Google in recent years — and rightly so. More and more studies are confirming that the ecosystem of microorganisms living in your gut isn't just a passenger in your digestion: it's a functional organ that directly influences your physical, mental and immunological health.
But what exactly is the gut microbiota? How does it work? What happens when it becomes unbalanced? In this guide, we answer all of those questions with the latest evidence.
Article Contents
The gut microbiota is the collection of living microorganisms – bacteria, viruses, fungi, archaea, and protozoa – that primarily inhabit the human colon. They aren't a collection of intruders: they are permanent residents that have been co-evolving with our species for millions of years.
Each person harbours approximately 160 different bacterial species, although the complete ecosystem can contain more than 1,000 different species distributed throughout the entire digestive tract. Their total weight is around 200 grams, comparable to that of an organ like the liver.
38 Bbacteria in the | 1.000+bacterial species | 9.9 millionmicrobial genes | 28%of people know |
Microbiota vs. Microbiome Although they are used as synonyms, they are not the same. The microbiota refers to the microorganisms themselves. The microbiome also includes their genes and their metabolites: the complete functional set of the ecosystem.
Colonisation begins at birth: babies born vaginally acquire a microbiota similar to maternal vaginal flora, while those born via C-section have profiles closer to those of the skin or environment. These first few weeks are crucial, as the neonatal microbiota influences the immune system's development for life.
Far from being limited to digestion, the gut microbiota participates in processes that affect the entire body. These are its most important functions:
🔥 Metabolismo y nutrición
Fibre is fermented, producing short-chain fatty acids such as butyrate, which is essential for nourishing colon cells and reducing inflammation. Vitamins K and B vitamins are also synthesised, and the absorption of minerals like calcium, iron, and magnesium is improved.
🛡️ Defensa inmunológica
It occupies receptors in the intestinal lining, produces antibacterial substances (bacteriocins), and prevents the proliferation of pathogens. Furthermore, it trains and modulates the immune system, favouring balanced responses and reducing the risk of allergies and autoimmune diseases.
🧱 Protección de la barrera intestinal
Butyrate and other metabolites maintain the integrity of the intestinal lining, preventing so-called “leaky gut” which can trigger systemic inflammation.
🧠 Comunicación cerebro-intestino
Through the gut-brain axis, the microbiota influences the production of neurotransmitters such as serotonin (90% of which is produced in the gut) and GABA, directly affecting mood, stress, and cognition.
⚖️ Regulación metabólica
Certain microbial compositions are associated with a higher risk of obesity, insulin resistance and type 2 diabetes. A diverse and balanced microbiota helps regulate body weight and lipid metabolism.
One of the most fascinating recent scientific findings is that the gut and the brain constantly communicate bidirectionally. This connection, known as the microbiota-gut-brain axis, is now one of the most promising research fields.
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The microbiota produces neurotransmitters and their precursors which travel to the brain via the vagus nerve and the bloodstream. Chronic stress, in turn, modifies the composition of the microbiota, reducing serotonin production and creating a cycle that can affect mood, anxiety, and sleep.
The most recent research suggests that certain interventions targeting the microbiota could be adjunctive treatments for anxiety and depression, although this field still requires further clinical evidence before precise therapeutic recommendations can be made.
Intestinal dysbiosis is the scientific term for an imbalance in the microbiota: an alteration in the quantity, quality, or distribution of the species that make it up. Only 1 in 3 people have heard this term, even though its consequences are widely known.
Factors that alter the microbiota
Ultra-processed diet High in sugar and low in fibre; reduces microbial diversity within weeks.
Antibiotics They eliminate pathogenic bacteria but also damage beneficial microbiota. The impact can last for months.
Chronic stress It alters intestinal permeability and negatively modifies bacterial composition.
Sedentary lifestyle A lack of exercise reduces microbial diversity and the systemic anti-inflammatory effect.
Diseases and associated symptoms
Digestive symptoms: Bloating, gas, diarrhoea, constipation, irritable bowel syndrome (IBS) and SIBO.
Systemic symptoms: Chronic fatigue, headaches, skin problems, allergies, asthma and mood swings.
Associated illnesses Obesity, type 2 diabetes, inflammatory bowel disease (IBD) and an increased risk of certain cancers.
The good news is that the microbiota is mouldable. Diet is its main modulator, and changes in diet have an effect on its composition in as little as 72 hours. Here are the strategies with the strongest scientific backing:
01 Over 30 plants a week
Studies show that consuming more than 30 different plant species per week promotes a more diverse and anti-inflammatory microbiota.
02 Prioritise fermentable fibre
Garlic, onion, leek, asparagus, oats, and green banana are natural prebiotics that feed your beneficial bacteria.
03 Include fermented foods
Yoghurt, kefir, sauerkraut, kimchi and miso provide natural probiotics. Extra virgin olive oil also has a documented prebiotic effect.
04 Manage stress
Meditation, mindful breathing, yoga, and outdoor walks reduce cortisol and protect microbial diversity.
05 Exercise regularly
Moderate aerobic exercise improves gut microbiota diversity and has a potent systemic anti-inflammatory effect.
06 Use antibiotics wisely
Only when they are necessary and always under medical prescription. Consider a course of microbiota rehabilitation after treatment.
How long does it take for the gut microbiota to recover?
It depends on the degree of dysbiosis. After antibiotic treatment, the microbiota can take between 1 and 6 months to partially recover. With dietary changes, some markers improve in as little as 2-4 weeks, although full recovery of diversity may require months or years of consistent habits.
How do I know if I have a healthy microbiome?
There is currently no clinically validated definition of an “ideal” microbiome. Microbiome tests analyse a stool sample and identify which microorganisms are present. However, these analyses should always be interpreted in a clinical context: the results are informative, not diagnostic.
Does the gut microbiota affect weight?
Yes. Certain microbial profiles are associated with greater calorie extraction from food, increased inflammation, and poorer regulation of satiety signals. A low-diversity microbiota is a risk factor for obesity with metabolic comorbidities, although it is not the sole determinant.
Does stress damage the microbiota?
Yes, directly. Chronic stress modifies bacterial composition, increases intestinal permeability and reduces intestinal serotonin production. This alteration, in turn, can aggravate stress, creating an important bidirectional cycle that needs to be interrupted.
Do babies born by Caesarean section have a worse microbiome?
Babies born by C-section have a different initial microbiome, with fewer beneficial bacteria from the vaginal canal. This is associated with a higher risk of allergies, asthma, and autoimmune diseases. Breastfeeding and early exposure to natural environments can help compensate for these differences.
For decades, medical science treated the gut as a simple digestive tube. Today we know it's an intelligent organ,
The vaginal microbiome is one of the most studied microbial ecosystems and, at the same time, one of the most unknown.