Immunity (and nutrition)
The body's defences against attack (viruses, bacteria), strongly influenced by diet, the microbiota, sleep and lifestyle.
The immune system protects against infections and abnormal cells. It combines innate immunity (a fast, non-specific defence) and adaptive immunity (a specific response, with memory). Nutrition and lifestyle modulate it powerfully.
The gut, headquarters of immunity: a central fact, as about 70% of immune cells live in the gut (see gut barrier). The microbiota constantly “trains” and regulates immunity. A diverse, balanced microbiota means better-calibrated immunity (neither too weak nor excessive or autoimmune). This is why gut health is at the heart of immunity.
Key nutrients for immunity (beyond vitamin C): the “vitamin C against colds” reflex is very reductive. Immunity depends on an orchestra of nutrients
- Vitamin D: powerfully modulates immunity; deficiency (common in winter) is associated with more respiratory infections
- Zinc: crucial (lozenges shorten colds); deficiency means weakened immunity
- Vitamin C: useful but its role is overrated (it slightly shortens duration, it does not prevent)
- Selenium, iron, copper, vitamin A: immune cofactors
- Protein: antibodies and immune cells are made from it
- Omega-3: regulate inflammation
The non-dietary pillars (often neglected):
- Sleep: THE underestimated pillar, as sleep deprivation clearly weakens immunity (fewer antibodies after vaccination, more infections). A good night beats many supplements
- Chronic stress: prolonged cortisol depresses immunity
- Moderate physical activity: strengthens immunity (but excess or overtraining weakens it temporarily)
- Microbiota (fibre, fermented foods)
Beware of “immune boost” marketing: you do not “boost” immunity like an engine. The aim is a balanced immunity (an “overactive” immune system causes allergies and autoimmunity). “Immunity” supplements are mainly useful in cases of real deficiency. In a well-nourished person, they add little.
In practice: a varied diet (covering the key micronutrients), caring for the microbiota, enough sleep, stress management and moderate activity. No miracle recipe, but an overall balance.