Every winter, I find myself suffering from colds and fatigue. I take vitamins, I sleep more, I watch my diet. But am I moving enough? Regular physical activity is one of the least known, yet best documented, factors in immune health.
The link between exercise and immunity is complex and fascinating: it is not only a question of strengthening the defenses, but of recalibrating an entire system which, in the event of a sedentary lifestyle, tends towards a state of chronic low-grade inflammation, one of the most deleterious processes for long-term health. Here's what the science says, and what I can actually do.
1. How exercise modulates my immune system
The immune system is made up of two complementary arms: innate immunity (rapid, non-specific response) and adaptive immunity (specific response, with memory). Physical exercise acts on both, with different effects depending on the dose and intensity.
2. The J-curve: the dose makes the medicine
The relationship between exercise and immunity follows a J-curve: moderate physical activity boosts immunity below baseline, while very intense, prolonged exercise can temporarily depress it.
- ●Sedentary activity (no exercise): Suboptimal immune system, chronic low-grade inflammation, higher than average risk of infection.
- ●Regular moderate activity (WHO recommendations): this is the optimal zone. 10 to 30% reduction in the risk of upper respiratory tract infections, better response to vaccines, reduced inflammation.
- ●Very intense and prolonged exercise (competitive athletes): with the open window theory, 3 to 72 hours after very intense exercise sees a temporary depression of immunity, increasing the risk of infection.
The practical conclusion: for the vast majority of us, moving towards more moderate activity is always beneficial for immunity. It is only in cases of intense and prolonged training (marathons, triathlons) that particular attention to recovery is necessary.
3. Exercise, chronic inflammation and systemic diseases
Chronic low-grade inflammation is today recognized as a central mechanism in the development of numerous diseases: cardiovascular diseases, type 2 diabetes, certain cancers, neurodegenerative diseases, depression. It is characterized by high levels of inflammatory markers (CRP, IL-6, TNF-alpha) in the absence of acute infection.
Regular exercise is one of the most effective natural anti-inflammatories identified by research. The contracting muscle releases myokines (including IL-6 at low doses) which exert a powerful systemic anti-inflammatory effect. Several studies show a 30 to 40% reduction in inflammatory markers in active versus sedentary people.
- ●Reduction in CRP (C-reactive protein) by 35% after 12 weeks of regular moderate activity
- ●Reduction of TNF-alpha (pro-inflammatory cytokine) by 20 to 30% in active people
- ●These effects are independent of weight loss, exercise is anti-inflammatory in itself
4. Physical activity and prevention of certain cancers
The link between physical activity and reduced risk of certain cancers is one of the strongest in preventive oncology. Mechanisms involved include reducing chronic inflammation, hormonal regulation, improving immune surveillance, and reducing fat mass.
5. Microbiota, exercise and immunityResearch over the last ten years has highlighted a fascinating link between physical activity, intestinal microbiota and immunity. The microbiota, the billions of bacteria that populate my intestine, plays a central role in immune regulation: 70% of immune cells are found in the intestinal level.
Regular physical exercise favorably modifies the composition and diversity of the microbiota: it increases butyrate-producing bacteria (a short-chain fatty acid with powerful anti-inflammatory effects) and reduces bacteria associated with inflammation. A study published in Gut (Clarke et al., 2014) showed that athletes have significantly higher microbiotic diversity than sedentary people. A health check allows you to evaluate your inflammatory and immune markers and identify priority levers of action. 14px;font-weight:700;color:#006064;font-size:1.1rem">💡 Tips to remember
- Regular moderate physical activity reduces by 10 30% the risk of upper respiratory tract infections, one of the most concrete and most immediately perceptible immune benefits. many diseases.
- The exercise-immunity relationship follows a J-shaped curve: moderate activity is optimal. For the vast majority, moving toward more activity is always beneficial for natural defenses.
- Regular physical exercise increases the diversity of the intestinal microbiota, the seat of 70% of immune cells, and promotes bacteria with anti-inflammatory effects.
- A health check-up allows you to assess your inflammatory markers (CRP, lipid profile) and identify whether your level of physical activity is sufficient to protect your long-term immune health.
