Probiotics and immunity: how your microbiota protects you from colds
Winter is coming, and with it, a slew of colds. Have you noticed? On average, adults catch two to three colds per year. However, some people get through the cold season unscathed.
This difference is no coincidence: it can largely be explained by the state of the microbiota and the quality of the immune response.
What if the key to boosting your immunity and preventing colds lay in your gut?
Discover how your gut directly influences your immune defenses and how probiotics can become your best allies for facing winter with peace of mind.
Understanding the common cold: a common but exhausting viral infection
Colds are very common viral infections caused mainly by rhinoviruses. Localized in the nose and throat, they last an average of 3 to 7 days. A stuffy nose, sneezing, sore throat… These are all symptoms that disrupt your daily life.
How do you catch a cold?
Colds are mainly transmitted in two ways:
Through direct contact: by touching contaminated surfaces (door handles, keyboards, etc.) and then touching your face. Viruses can survive for several hours on these surfaces.
Through the air: via droplets suspended in the air when an infected person sneezes or coughs.
Once inside your body, the viruses enter the respiratory tract where they multiply rapidly. This invasion triggers an inflammatory response: your immune system springs into action to eliminate the intruder. It is this battle that causes the unpleasant symptoms of a cold.
Why do some people get sick more often?
The immune response varies considerably from person to person. Clinical studies show that people with a strong immune system are less prone to respiratory infections and recover more quickly.
When the immune response is slow or unbalanced, three problems arise:
1.The virus has more time to multiply.
- Inflammation becomes excessive, aggravating symptoms.
- Healthy tissue can be attacked, aggravating symptoms and promoting secondary infections (sinusitis, bronchitis, etc.).
A well-regulated immune system is therefore essential for preventing colds. And this regulation depends largely on your gut microbiota. (1)
The key role of your microbiota in immune defense
The body is home to several trillion microorganisms (bacteria, viruses, fungi, etc.) that play an essential role in its functioning. The best known is the gut microbiota, but others are also important for staying healthy during the winter.
The gut microbiota: the conductor of your immunity
Did you know? 70% of your immune cells are found in your gut. A balanced gut microbiota plays a fundamental role in immunity, acting both locally in the gut and remotely throughout the body.
What a healthy gut microbiota does:
- Stimulates immune cells (T lymphocytes, NK cells) to make them more effective
- Modulates the production of cytokines, inflammatory molecules that must remain balanced to avoid an excessive reaction
- Strengthens the intestinal and respiratory mucous membranes, the first physical barriers against viruses
- Limits the establishment and adhesion of pathogens through spatial competition or competition for nutrients
- Synthesizes vitamins essential to the immune system (vitamins B and K)
A healthy microbiota enables a rapid but controlled immune response. It thus limits the onset, intensity, and duration of cold symptoms. (1)
The pulmonary microbiota: an overlooked but essential player
Until a few years ago, the lungs were considered sterile organs. Today, research reveals the opposite: the respiratory tract is home to a rich and active pulmonary microbiota.
Although it contains significantly fewer microorganisms than the gut, its influence is considerable:
- Maintains immune balance and modulates local inflammation in the lungs
- Prevents colonization by pathogens
- Facilitates repair of lung tissue after infection.
A balanced pulmonary microbiota helps you better resist respiratory infections, including colds. (2)
The nasal microbiota: the first line of defense
Often overlooked, the nasal microbiota is nevertheless on the front line against cold viruses. Research is just beginning to explore its potential, but the initial findings are promising.
Recent studies show that certain nasal microbial profiles are associated with a higher risk of respiratory infections in older people. (3)
Taking care of your nasal microbiota (by avoiding overly aggressive washing and keeping your mucous membranes well hydrated) could therefore be an additional preventive strategy.
The gut-lung axis: when your stomach protects your lungs
Here’s a fascinating discovery: your gut and lungs are constantly communicating via the gut-lung axis.
This connection explains why taking care of your gut microbiota can boost your respiratory immunity and protect you from colds.
Two-way communication
When the gut microbiota is out of balance (dysbiosis), your respiratory defenses weaken. Conversely, a respiratory infection can disrupt your gut flora, creating a vicious cycle.
This interaction occurs via two main pathways:
- The mesenteric lymphatic system: a network of vessels that transports immune cells from the gut to the lungs
- The bloodstream: it distributes the molecules produced by your gut microbiota throughout the body.
Messenger molecules that strengthen your defenses
Your gut microbiota produces substances that travel to your lungs to strengthen your defenses:
Short-chain fatty acids (SCFAs): these metabolites, produced by the fermentation of dietary fiber by gut bacteria, strengthen the pulmonary barrier, reduce excessive inflammation, and support the antiviral response.
Bile acids: synthesized in the liver and transformed by the microbiota, they regulate the activity of the pulmonary immune system and influence the composition of the respiratory microbiota.
Lipopolysaccharides (LPS): components of certain bacteria in the microbiota, they modulate the pulmonary immune balance.
These exchanges ensure the proper coordination of the immune response throughout the body. A balanced gut thus helps the lungs to better defend themselves against infections, such as colds.
The gut-lung axis illustrates why a holistic approach to health, particularly through probiotics, can have an impact on cold prevention. (2)
Factors that weaken you in winter
Winter puts your microbiota and immunity to the test. Understanding these factors allows you to better protect yourself
1. Chronic stress: the invisible enemy of your microbiota
Long-term stress disrupts the balance of your gut microbiota via the gut-brain axis.
Cortisol (the stress hormone) alters the microbial composition, increases intestinal permeability, and promotes systemic inflammation. The result: your immune response weakens, making you more vulnerable to colds
2. Indoor heating: friend of comfort, enemy of mucous membranes
Excessive heating (>22°C) dries out the ambient air. Your nasal and respiratory mucous membranes dry out, lose their ability to trap viruses, and become more permeable. In addition, dry air promotes the survival and spread of viruses in the environment.
3. Cold air: double stress for your respiratory tract
Cold, dry winter air also dries out the respiratory mucous membranes, reducing the production of protective mucus. In addition, it slows down the activity of the cilia that normally remove pathogens.
4. Vitamin D deficiency: winter’s immune weakness
In winter, exposure to sunlight decreases dramatically, reducing your vitamin D synthesis. (4)
However, this vitamin is crucial for immunity: it activates immune cells, modulates inflammation, and positively influences the composition of the gut microbiota.
5. Lack of physical activity and an unbalanced diet
Winter often means a more sedentary lifestyle and a richer diet with less variety in terms of plant-based foods. These two factors reduce the diversity of your gut microbiota, weakening your immunity.
Probiotics: allies in strengthening the microbiota and fighting colds
A 2022 meta-analysis shows that consuming targeted probiotics has a positive effect on the composition of the gut and lung microbiota. By restoring microbial balance, probiotics promote an appropriate and effective immune response. (1)
Probiotics colonize the gut microbiota and act in two main ways:
1. Activation of the immune system
Once in your gut, probiotics stimulate the production of immunomodulatory molecules. This activation occurs simultaneously locally (in the gut) and remotely (in the lungs, via the gut-lung axis).
Specifically, they:
- Increase the activity of Natural Killer (NK) cells, which destroy infected cells
- Stimulate the production of immunoglobulin A (IgA), antibodies that protect the mucous membranes
- Balance the production of pro- and anti-inflammatory cytokines
- Strengthen the integrity of the intestinal barrier, limiting the passage of pathogens.
2. Direct protection against pathogens
Probiotics create an environment that is hostile to cold viruses :
– Strengthening the mucous membrane: they increase the production of protective mucus and tighten the junctions between cells, preventing viruses from attaching.
– Spatial competition: by colonizing your intestine, they reduce the space available for pathogens. (2)
– Production of antimicrobial substances : certain strains produce bacteriocins, organic compounds, or acids that inhibit viral growth.
Probiotics and colds: when to take supplements?
Probiotics help fight colds. But in practical terms, should they be used preventively or once the infection has set in?
A 2020 review compiled the results of several meta-analyses:
Preventive use against colds
Taking probiotic supplements during the winter months can:
- Reduce the frequency of colds
- Decrease recurrence: fewer successive episodes of infection
- Improve the innate and adaptive immune response: your immune system reacts faster and more effectively
- Reduce the use of antibiotics: fewer complications requiring treatment.
To promote faster recovery
When the first symptoms appear, probiotic supplementation can:
- Shorten the duration of symptoms
- Reduce the intensity of the cold, making it less debilitating
- Speed up recovery: particularly beneficial for children, athletes, and anyone exposed to stress or fatigue
- Limit complications: fewer secondary infections
The crucial importance of choosing the right strain: not all probiotics are created equal.
Clinical studies show that results depend entirely on the strain chosen. (1), (2)
That’s why it’s essential to choose a dietary supplement whose strains have been clinically tested to boost immunity and fight colds.
FAQ: Your questions about probiotics, immunity, and colds
How long should you take probiotics to boost your immunity?
For optimal effectiveness in preventing colds, supplementation for 3 to 6 months is recommended, ideally starting before the winter season. The first effects may appear after 2 to 4 weeks of regular use.
Can you take probiotics when you already have a cold?
Yes, absolutely. Studies show that starting supplementation as soon as symptoms appear helps reduce their duration and intensity. However, prevention is still the best approach.
Do probiotics replace other cold prevention measures?
No, they are an effective supplement but do not replace preventive measures (hand washing, airing rooms), a balanced diet, sufficient sleep, and regular physical activity.
What is the difference between probiotics and prebiotics?
Probiotics are beneficial living microorganisms, while prebiotics are dietary fibers that feed these good bacteria. For maximum effectiveness, combine both in your diet (this is known as synbiotics).
Are there any side effects to probiotics?
Probiotics are generally very well tolerated. If you have a severely weakened immune system, seek advice from a healthcare professional.
Can children take probiotics to prevent colds?
Yes, several studies have demonstrated the effectiveness and safety of probiotics in children in reducing the frequency and duration of respiratory infections. Choose formulas that are appropriate for their age.
Conclusion: take control of your immunity
By understanding the role of the gut microbiota, the lung microbiota, and the gut-lung axis, you can have a lasting impact on your immunity.
Supplementing with targeted probiotics, combined with a healthy lifestyle, helps to:
- Prevent the onset of colds
- Reduce the duration and intensity of symptoms
- Strengthen your immunity in a comprehensive and sustainable way.
Don’t wait until you get sick: prepare yourself now to get through the winter in great shape.
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