Winter immunity: what really works to boost it

By Marie, dietician and specialist advisor in nutritional supplements at Pleine Forme
15 years of experience in natural solutions and immune system support

 

You catch one cold after another starting in October. Your child brings home every virus from school. You feel constantly tired, vulnerable, as if your body can no longer defend itself. Every winter, it's the same story.

What if it wasn't inevitable? What if you could transform your immune system into a veritable fortress, naturally, without waiting to get sick to take action?

In my 15 years at Pleine Forme, I've helped hundreds of families drastically reduce their winter infections by adopting the right strategies. The key? Act BEFORE winter, not during .

In this guide, I reveal scientifically validated methods (not "old wives' tales") to sustainably strengthen your immunity: targeted nutrition, effective supplements, protective measures.

 

🔍 Is your immunity weakened? Quick self-assessment

Please check the symptoms you have experienced for the past 3 months:

Common infections :

• ☐ More than 3 colds/year

• ☐ Lingering infections (>10 days)

• ☐ Sore throats, sinusitis, recurrent bronchitis

• ☐ Frequent cold sores

Physical signs :

• ☐ Chronic fatigue even after rest

• ☐ Slow healing (wounds, cuts)

• ☐ Dry skin, eczema

• ☐ Brittle nails, fragile hair

Digestive problems :

• ☐ Regular bloating

• ☐ Disrupted bowel movements (constipation/diarrhea)

• ☐ Recurrent candidiasis

• ☐ New food intolerances

Risk factors :

• ☐ Chronic stress (work, family)

• ☐ Sleep < 7 hours/night

• ☐ Unbalanced diet

• ☐ Sedentary lifestyle or physical overwork

✅ If you have checked 5 or more symptoms, your immunity urgently needs boosting. Follow this guide.

 

Why your immunity collapses in winter

The 5 factors that weaken your defenses

1. Cold dries out your mucous membranes. Cold (outdoor) and dry (heating) air dehydrates your respiratory mucous membranes, your first line of immune defense. As a result, viruses penetrate more easily.

2. Your cilia slow down. The cold slows the movement of the microscopic cilia in your nose, which are responsible for expelling viruses and bacteria. Your natural elimination system becomes less efficient.

3. Viruses love the cold; their lipid envelope solidifies, making them more resistant and allowing them to survive longer on surfaces (handles, keyboards...).

4. Spending more time indoors, in poorly ventilated spaces and close quarters, leads to accelerated transmission. A sneeze can project up to 40,000 droplets within an 8-meter radius.

5. Your vitamin D levels plummet in our latitudes; from November to March, the angle of the sun is insufficient for vitamin D synthesis. Yet, 80% of French people are deficient in winter. This deficiency directly weakens the immune system.

Signs of a weakened immune system

⚠️ Frequent infections (>4 colds/year)
⚠️ Prolonged infections (colds lasting 2-3 weeks)
⚠️ Persistent fatigue despite adequate rest
⚠️ Slow healing (protracted wounds)
⚠️ Recurrent digestive problems (70% of immunity is in the gut)

💡 Key takeaway : Your immunity doesn't suddenly collapse. It's a gradual weakening due to the accumulation of adverse factors. Good news: you can reverse this trend.

 

Nutrition: the foundation of your winter immunity

70% of your immune cells are in your gut. What you eat directly influences your ability to defend yourself.

The 8 star foods for immunity

1. Citrus fruits (orange, lemon, grapefruit)

• Vitamin C: 200-300% of the RDA per 2 oranges

• Action: Stimulates white blood cell production, powerful antioxidant

• Consumption: 2 fruits/day minimum

2. Kiwi

• Champion vitamin C: 1 kiwi = 100% RDA

• Bonus: Vitamin E, antioxidants

• Tip: Have it at breakfast

3. Garlic and onion

• Allicin: Antimicrobial and antiviral sulfur compound

• Action: Stimulates macrophages (virus-eating cells)

• Dosage: 1-2 cloves of raw garlic per day (crushed 10 minutes before cooking)

4. Ginger

• Gingerol: Anti-inflammatory, antiviral

• Uses: Infusion (1 cm of fresh root/cup), cooking

• Frequency: Daily in winter

5. Oily fish (salmon, mackerel, sardines)

• Omega-3: Modulate inflammation, strengthen the intestinal barrier

• Natural Vitamin D: 100g salmon = 50% of the RDA

• Frequency: 2-3 times/week

6. Cruciferous vegetables (broccoli, cabbage, cauliflower)

• Sulforaphane: Stimulates detoxifying enzymes, strengthens innate immunity

• Vitamin C, beta-carotene

• Cooking method: Gentle steaming (preserves nutrients)

7. Squash (butternut, pumpkin)

• Beta-carotene: Pro-vitamin A, essential for your mucous membranes

• Action: Maintains the integrity of the respiratory/digestive barriers

• Serving size: 150-200g/day

8. Fermented foods (kefir, raw sauerkraut, kimchi)

• Natural probiotics: Nourish the gut microbiota

• Action: Strengthens the intestinal barrier, modulates immunity

• Consumption: Daily (1-2 tbsp)

Things to avoid (weaken the immune system)

❌ Refined sugar : Reduces white blood cell activity by 50% for 5 hours
❌ Ultra-processed foods : Disrupt your gut microbiota
❌ Excessive alcohol : Dehydrates mucous membranes, weakens your liver (an immune organ)
❌ Trans fats : Promote chronic inflammation
❌ Excessive dairy products : May increase mucus (if sensitive)

Sample menu for day 1 of optimal immunity

Breakfast :

• Plain kefir or yogurt + 1 kiwi + a handful of almonds

• Green tea (antioxidants) + 1 tsp manuka honey

Lunch :

• Lamb's lettuce/spinach salad + avocado (vitamin E)

• Grilled salmon + roasted squash + steamed broccoli

• 1 orange

To taste :

• Ginger-lemon infusion

• Dark chocolate square 70%+ (polyphenols)

Dinner :

• Butternut squash and red lentil soup (protein + beta-carotene)

• Fermented red cabbage salad (sauerkraut)

• 2 Brazil nuts (selenium)

Hydration: 1.5-2L water/day (herbal teas and broths count)

 

Micronutrition: The 5 supplements that change everything

Even with a balanced diet, some nutrients require supplementation in winter.

1. Vitamin D3 + K2 ⭐⭐⭐ (ESSENTIAL)

Why this is crucial :

• 80% of French people are deficient in nutrients during winter.

• Activates 200+ genes linked to immunity

• Reduces respiratory infections by 50% (studies)

Dosage :

• Children: 800-1000 IU/day

• Adults: 2000-4000 IU/day (October to March)

• With K2: Improves absorption, bone fixation

Recommended form : Oily drops (better absorption than capsules)

⚠️ Blood test recommended for precise measurement (target: 30-50 ng/ml)

2. Zinc bisglycinate ⭐⭐⭐

Actions :

• Maturation of immune cells (T lymphocytes)

• Reduces the duration of a cold by 33% if taken at the first sign of symptoms

• Direct Antiviral

Dosage :

• Prevention: 15 mg/day

• Reported infection: 30 mg/day (5-7 days)

Recommended form : Bisglycinate (80% bioavailability vs. 20% for oxide)

⚠️ Take at least 2 hours apart from iron supplements and with food (to prevent nausea)

3. Liposomal vitamin C ⭐⭐

Superiority of the liposomal form :

• Absorption 90% (vs 20% for the classic form)

• Passage through the bloodstream without digestive degradation

• Extended action (6-8h vs 2h)

Dosage :

• Prevention: 500-1000 mg/day

• Infection: 2000-3000 mg/day (divided doses)

Timing : Morning on an empty stomach or 30 minutes before a meal

4. Multi-strain probiotics ⭐⭐⭐

Key strains for immunity :

• Lactobacillus rhamnosus GG (respiratory infections)

• Bifidobacterium lactis (lymphocyte activation)

• Lactobacillus plantarum (intestinal barrier)

Dosage : Minimum 10 billion CFU/day

Treatment duration : 3 months (October-December), then 1 month out of 2

⚠️ Take in the morning on an empty stomach or at bedtime, 30 minutes before/after meals

5. Ultra-pure Omega-3 (EPA/DHA) ⭐⭐

Immune actions :

• They modulate inflammation (omega-6/omega-3 balance)

• They strengthen the membrane of immune cells.

• They regulate cytokine storms (severe infections)

Dosage : 1000-2000 mg EPA+DHA/day

Essential quality : EPAX or IFOS label (heavy metal purity)

Herbal medicine: plants that strengthen your defenses

1. Echinacea (Echinacea purpurea) ⭐⭐⭐

Action : Stimulates innate (macrophages, NK cells) and adaptive (lymphocytes) immunity

Usage :

• Prevention: 3-week/monthly treatment (October-February)

• At the first sign of symptoms: 3 times a day for 7-10 days

Form : Standardized dry extract or mother tincture

⚠️ Contraindication : Autoimmune diseases

2. Black elderberry (Sambucus nigra) ⭐⭐

Action : Powerful antiviral (flu, cold), reduces the duration of symptoms by several days

Use : Syrup or extract, at the first signs

Dosage : 15 ml syrup 4 times a day

3. Curcumin ⭐⭐

Action : Major anti-inflammatory, stimulates macrophages

Dosage : 500-1000 mg/day (liposomal form = 30× greater absorption)

Association : With piperine (black pepper) if not liposomal

4. Adaptogenic Mushrooms ⭐⭐⭐

Reishi (Ganoderma lucidum):

• Immunomodulator, adaptogen

• Dosage: 1000-3000 mg dry extract/day

Cordyceps :

• Increases energy and oxygenation

• Ideal if fatigue + infections

Umbrella Polypore :

• Rich in PSK/PSP (immunostimulating polysaccharides)

• Used to boost immunity

 

7 daily steps to avoid getting sick

1. Sleep: your immune cell factory

Objective : 7-8 hours/night, regular

Why : Production of interleukins and T lymphocytes during deep sleep

Tip : Go to bed before 11pm (peak melatonin production)

2. Moderate physical activity

Optimal : 30 minutes of brisk walking per day OR 150 minutes of moderate activity per week

Action : Stimulates lymphocyte circulation, reduces your cortisol (stress hormone)

⚠️ Harmful excess : Overtraining weakens immunity (open post-exercise window)

3. Handwashing (step #1)

When : Before meals (basically), after using public transport, the toilet, and after contact with public surfaces

How to : Lather for at least 30 seconds, between fingers, under nails

Alternative : Hand sanitizer (70%+) if no water is available

4. Daily ventilation

Frequency : 10-15 min, 2-3 times/day (even in winter)

Action : Dilutes virus concentration (×10-100 in confined indoor spaces)

Tip : Open windows wide, not just ajar.

5. Optimal hydration

Target : 1.5-2L/day

Why : Effective mucous membranes = moist (mucus captures viruses)

Drinks : Water, herbal teas, broths (avoid alcohol, excessive coffee)

6. Stress management (cortisol = enemy of immunity)

Validated techniques :

• Heart coherence: 5 min, 3 times/day (apps: RespiRelax, Kardia)

• Meditation: 10-20 min/day

• Yoga, Tai chi

• Nature contact: 20 min/day minimum

7. Limiting contacts during the epidemic phase

• Avoid exposure to crowds if possible

• Sneeze into your elbow (not your hands).

• Do not touch your face (eyes, nose, mouth = entry points)

• Disinfect frequently touched surfaces (handles, phone, keyboard)

 

Anti-infection protocol: from the first symptoms

Can you feel it coming on (itchy throat, sudden fatigue, chills)?

Act within 24 hours (critical window) :

Immediate :

✅ Rest: Cancel non-essential activities
✅ Hydration: 2-3L water/day + hot broths
✅ Liposomal Vitamin C: 2000 mg immediately, then 1000 mg × 3/day
✅ Zinc: 30 mg immediately, then 2 times/day (5 days)
✅ Echinacea: 3 times/day
✅ Elderberry: 15 ml syrup 4 times a day

Food :

✅ Garlic-ginger-lemon infusion
✅ Manuka honey (antimicrobial) directly by the spoonful, do not heat it!
✅ Avoid dairy products (if you have a lot of mucus)

Sleep : 9-10 hours + naps if possible

⚠️ Consult a doctor if : Fever >39°C for 3 days, difficulty breathing, or worsening symptoms

 

FAQ: Your questions about winter immunity

When should you start boosting your immunity?

Starting in September-October, before the arrival of viruses. An immune system strengthens in a minimum of 4-6 weeks.

Do vaccines prevent the body from naturally strengthening its immunity?

No, on the contrary. Vaccination and natural immune reinforcement are complementary. Vaccination leads to adaptive immunity, while a healthy lifestyle strengthens innate immunity.

Is it possible to overdose on vitamin C?

Difficult to take, it is water-soluble (excess is eliminated). Above 2000 mg, mild diarrhea is possible (sign of saturation). Reduce the dose.

Can children take the same supplements?

Yes, but in appropriate doses:

• Vitamin D: 800-1000 IU

• Zinc: 5-10 mg

• Probiotics: 5 billion CFU

• Vitamin C: 250-500 mg

Does intense exercise weaken the immune system?

Yes, if excessive. Beyond 90 minutes of intense effort, the immune system has a 3-72 hour "open window" (increased vulnerability). Moderation is key.

Do antibiotics permanently weaken the immune system?

Yes, they destroy the gut microbiota (which affects 70% of immunity). After treatment: probiotics are mandatory for 3 months to restore the gut flora.

 

Conclusion: Your action plan for a disease-free winter

After 15 years at Pleine Forme, I can say: a strong immune system is not built in 3 days, but is protected for a lifetime.

Your immunity checklist (to be applied NOW)

Nutrition :

✅ 2 fruits/day (including 1 citrus fruit or kiwi)
✅ Colorful vegetables at every meal
✅ Fatty fish 2 times/week
✅ Daily fermented foods
✅ Eliminate as much refined sugar as possible

October-March supplement :

✅ Vitamin D3+K2: 2000-4000 IU/day
✅ Zinc: 15 mg/day
✅ Probiotics: 10 billion CFU/day
✅ Liposomal Vitamin C: 500-1000 mg/day

Lifestyle :

✅ Regular 7-8 hour sleep
✅ Physical activity 30 min/day
✅ Stress management (heart coherence)
✅ Regular handwashing
✅ Ventilate 2-3 times/day

Expected results (if you follow 80% of the protocol):

• Month 1: Less fatigue, better sleep

• Month 2: Shorter infections if they occur

• Months 3+: Infection frequency divided by 2-3

My message to you

Your immune system isn't a genetic lottery. It's a direct reflection of your lifestyle, your nutrition, and your stress management. 70% of people who constantly get sick in winter simply have an undernourished, underhydrated, and overworked immune system.

At Pleine Forme, we support hundreds of families each year who transform their winter. No more endless colds, no more repeated absences, no more chronic fatigue. Just a peaceful winter, in top form.

Need personalized support? Our team is available to help you with:

• Nutritional and immunity assessment

• Selection of suitable supplements (quality, dosages)

• Customized protocol based on your profile

Together, let's transform your winter into a season of vitality!

 

Where can you buy quality immunity supplements?

At Pleine Forme, we rigorously select:

• Bioavailable Vitamin D3+K2

• High absorption zinc bisglycinate

• Clinically tested multi-strain probiotics

• Pharmaceutical grade liposomal vitamin C

• Certified ultra-pure Omega-3

Available: In store (free advice) or online (24-48 hour delivery)

 

Article written by Marie, a registered dietitian
Last updated: January 2026

⚠️ Medical warning

The advice in this article is for informational and preventative purposes only. It is not a substitute for medical advice. Consult a healthcare professional before taking any supplements, especially if you have a chronic condition, are pregnant, breastfeeding, or taking medication.