Autumn Reset: Immune Prep for Cold Months

5 measures + 5 ingredients with scientific evidence

October. The first colleagues arrive at the office with a runny nose, people cough on the subway, and the first scratchy throat strikes, and you think: Not again. While some resignedly go through one cold after another, there's a better way—not a magic trick, but a well-thought-out protocol based on solid science.

The cold season challenges your immune system on several levels at once: Less daylight reduces vitamin D production, lower temperatures impair blood flow to the mucous membranes, and dry, heated air weakens your first line of defense. Added to that in cities: more time spent indoors, higher virus density, and constant stress.

This article shows you the 5 most effective measures and the 5 ingredients with the strongest scientific evidence to specifically strengthen your immune system. Not through exaggerated promises, but through proven strategies and targeted nutritional support – optimized for everyday urban life.

The 5 most important measures for a strong immune system

1. Exercise – The moderate immune booster

Regular, moderate exercise is one of the most effective yet underestimated immune strategies. When you exercise, you mobilize immune cells, improve blood circulation, and reduce inflammatory markers. Studies clearly show that people who exercise moderately have a lower risk of respiratory infections [1].

The J-curve : This is where things get interesting. Research shows a curved relationship between exercise and immune function. Moderately active individuals are best protected, while both inactive individuals and elite athletes are at increased risk of infection [1]. The reason: Overly intense exercise can temporarily weaken the immune system—the so-called "open window effect," in which you are more susceptible to infections for 3-24 hours after intense exercise.

What does "moderate" mean?

You should still be able to talk while exercising, but you should definitely work up a sweat. The ideal amount: 30-45 minutes, 4-5 times per week. This could be jogging, cycling, swimming, strength training, or brisk walking.

For city dwellers: Make the most of your commute. Get off the train two stops early and walk the rest of the way, or cycle instead of taking the subway. Outdoor exercise combines an immune boost with natural daylight—a double benefit during the darker months.

Source: Nieman DC, Wentz LM. The compelling link between physical activity and the body's defense system. J Sport Health Sci. 2019.

2. Cold exposure – promising, but with realistic expectations

Regular cold stimuli can positively influence certain immune parameters, but clinical evidence is still limited. The often-cited Dutch study with over 3,000 participants found 29% fewer self-reported sick days in people who regularly took cold showers [2]. Importantly, these were subjective reports, not objective evidence of infection, and placebo effects are possible. The mechanisms are biologically plausible: cold stimuli activate the sympathetic nervous system, stimulate the production of white blood cells, and train thermoregulation. For some people, this can be a useful supplement—with realistic expectations.

How to try it: Start with 30 seconds of cold water at the end of your normal shower. The water should be cool, but it doesn't have to be icy cold. Gradually increase to 1-2 minutes over several weeks. Alternating showers (2-3 minutes warm, 30-60 seconds cold) are particularly effective at training your adaptability.

Important: If you have a severe cold or feel under the weather, take a break. During this phase, your body needs rest, not additional stress.

For city dwellers: Cold stimuli can improve your resilience to constant temperature changes (cold subways, overheated offices, drafty streets). Consider it training, not a guarantee.

Source: Buijze G et al., The Effect of Cold Showering on Health and Work. PLoS ONE 2016

3. Sleep – The most powerful natural immunotherapy

If there's one non-negotiable measure, it's sleep. The data is clear: Even a single night with less than 6 hours of sleep reduces your natural killer cell activity by up to 72% [3]. People with chronic sleep deprivation have a three times higher risk of becoming infected after exposure to the virus.

While you sleep, T cells are activated, antibodies are produced, and inflammation is regulated. The vaccine response is also twice as strong when the body is well-rested as when it is sleep-deprived. Sleep is not a luxury, but a biological necessity for optimal immune function.

The optimal sleep strategy: 7-9 hours per night, with consistent bedtimes – even on weekends. Your body clock thrives on regularity. The bedroom should be dark (avoid even small light sources), cool (16-18°C), and quiet.

Practical tips:

  • Avoid screens 1 hour before bedtime (blue light suppresses melatonin)
  • Avoid alcohol in the evening (disrupts the sequence of sleep phases)
  • Establish an evening ritual that signals to your body: Now it’s bedtime

For city dwellers: Noise pollution is a massive sleep killer in the city. Invest in good earplugs or use white noise apps to block out street noise. Blackout curtains are also useful, especially if streetlights shine into the bedroom.

Source: Irwin M. et al., Partial night sleep deprivation reduces natural killer and cellular immune responses in humans. FASEB J. 1996.

4. Hydration & Humidity – Mucous membrane protection from inside and out

Your mucous membranes in your nose, throat, and respiratory tract are your first line of defense against pathogens. They produce mucus that traps viruses and bacteria before they can penetrate deeper. Dry mucous membranes can't fulfill this task—they become chapped, irritated, and vulnerable. Heating periods often result in humidity below 30%; 40-60% is optimal. Research shows that low humidity impairs mucociliary clearance (the removal of pathogens), the epithelial repair capacity, and the production of interferon—an important antiviral signal [4]. At the same time, viruses remain infectious in the air longer at low humidity.

How to protect your mucous membranes:

  • Drink enough: 35ml per kg of body weight (about 2.5 liters for 70kg)
  • Use a humidifier in the bedroom and ideally also in the office
  • Ventilate regularly: 3 times a day, short bursts of ventilation for 5-10 minutes
  • Optional: Nasal irrigation with isotonic saline solution (1-2x daily) moistens the nasal mucosa and mechanically flushes out pathogens. Be aware that your body can quickly become addicted to this. Therefore, it's only recommended in truly dry conditions, and even then, only intermittently.

For city dwellers: In offices and on public transport, you have little control over the humidity. Hydration from within is all the more important. Carry a water bottle with you – in the hustle and bustle of the city, it's easy to forget to drink.

Source: Kudo E. et al., Low ambient humidity impairs barrier function and innate resistance against influenza infection. PNAS 2019.

5. Stress management – ​​getting cortisol under control

Chronic stress is one of the most powerful immune killers of all. When you're chronically stressed, your body continuously releases cortisol – a hormone that's vital for survival in acute situations, but massively suppresses immune function when chronically elevated. Studies show that chronic stress increases the risk of infection by a factor of 2-3. Just 10-20 minutes of daily meditation or mindfulness exercises can measurably reduce stress hormones and improve immune function [5]. The effects are even demonstrable after 8 weeks of regular practice.

Practical stress reduction:

  • Establish a daily relaxation practice: meditation, breathing exercises (e.g. 4-7-8 technique: inhale for 4 seconds, hold for 7 seconds, exhale for 8 seconds), yoga or progressive muscle relaxation
  • Plan conscious breaks: every 90 minutes, take a 5-minute break in which you get up and move around
  • Spend time in nature: Just 2 hours a week in a park or forest has been proven to reduce cortisol levels
  • Set limits on digital accessibility: Constant availability is a massive stressor

For city dwellers: Constant low-level stress caused by noise, crowds, time pressure, and constant availability is the urban reality. This is precisely why you need active countermeasures. Even taking a lunch break in the nearest park instead of at your desk can make a significant difference.

Source: Black DS, Slavich GM. Mindfulness meditation and the immune system. Ann NY Acad Sci. 2016.

Title

The 5 ingredients with the strongest scientific evidence

Measures form the basis – ingredients provide targeted reinforcement. No capsule can compensate for poor sleep, chronic stress, or lack of exercise. But if the basics are right, certain nutrients can powerfully support your immune system during high-risk phases.

1. Vitamin C – Shortens duration, but does not prevent infections

Vitamin C is one of the most well-researched vitamins for the immune system. It protects immune cells as an antioxidant, supports phagocytosis (the "eating" of bacteria by immune cells), and promotes interferon production.

The scientific evidence: The comprehensive Cochrane meta-analysis with over 11,000 participants shows a differentiated picture [6,7]: Regular vitamin C intake shortens the duration of colds by about 8% in adults and by 14% in children. However, the frequency of infections is not affected in the general population. One significant exception: In people subjected to extreme physical exertion (marathon runners, soldiers in polar regions), vitamin C halves the risk of colds. The mechanism: High-intensity exercise produces oxidative stress, which vitamin C can buffer.

What this means in practical terms: Vitamin C doesn't prevent colds, but it can help you recover faster. This is especially relevant for people with increased needs: smokers (including those exposed to secondhand smoke), athletes, and people exposed to stress.


Concrete advantages:

  • Antioxidant protection of immune cells
  • Supports the barrier function of skin and mucous membranes
  • 8-14% shorter duration of colds when taken regularly
  • Dosage: 500-1000mg daily, very safe

For city dwellers: Air pollution, secondhand smoke, and chronic stress increase oxidative stress in your body—and thus your need for vitamin C. It's useful as part of an overall protocol, not as a mono-supplement.


Source : Hemilä H, Chalker E. Vitamin C for preventing and treating the common cold. Cochrane Database Syst Rev. 2013.

2. Vitamin D – the immune system modulator

Vitamin D isn't a traditional vitamin, but a hormone that your body can produce itself – but only with sufficient UVB radiation. From October to March, the sun's intensity in Germany is insufficient. At the same time, few foods contain significant amounts.

The scientific evidence: The BMJ meta-analysis of 25 randomized controlled trials and over 10,900 participants provides clear results [8,9,10]: Vitamin D supplementation reduces the risk of acute respiratory infections by 12% in the general population. In people with vitamin D deficiency (<25 nmol/L), the risk decreases by an impressive 42%.

The dosage is crucial: Daily or weekly administration works. High-dose bolus doses (every 1-3 months) are ineffective, according to studies [8,10].

How it works : Vitamin D regulates the expression of antimicrobial peptides—natural antibiotics your body produces (cathelicidins, defensins). It modulates T-cell responses and prevents excessive inflammatory reactions. Almost all immune cells have vitamin D receptors.

Concrete advantages:

  • Promotion of antimicrobial defense mechanisms Modulation of inflammatory processes
  • Up to 42% fewer respiratory infections in case of deficiency
  • Support of T cell function

Classification:

  • Evidence level: Very good to strong (especially in cases of deficiency)
  • Safety: Very high at 2000-4000 IU/day
  • Relevance: Practically all people in Germany in the winter half-year

For city dwellers : Office work, public transportation, indoor sports—your skin barely sees daylight for months. Vitamin D deficiency is more the rule than the exception among city dwellers in winter. If you were to supplement only one nutrient, it should be vitamin D.

Source : Martineau AR et al. Vitamin D supplementation to prevent acute respiratory tract infections. BMJ. 2017.

3. Zinc – Shortens the duration of colds when taken early

Zinc is an essential trace element involved in over 300 enzymatic reactions. It plays a central role in almost all aspects of the immune system—from T cell development to macrophage function and mucous membrane barrier function.

The scientific evidence : A systematic review of 17 randomized controlled trials shows [3,11,12] that zinc lozenges can shorten the duration of a cold in adults by an average of 1.6 to 2.6 days when taken within 24 hours of symptom onset. The optimal dosage is over 75 mg of elemental zinc per day.

Important : The form is crucial. Lozenges work significantly better than regular tablets or syrup because zinc acts locally in the throat, inhibiting the proliferation of rhinoviruses there.

The catch : Side effects are relatively common. Approximately 10-20% of users report a metallic taste and nausea. Long-term high-dose use carries the risk of copper deficiency.

Concrete advantages:

  • Inhibits the proliferation of cold viruses (especially rhinoviruses)
  • Stabilizes the mucosal barrier
  • Supports T cell function and NK cells
  • 1.6-2.6 days shorter cold duration when taken early

Classification:

  • Evidence level: Good to very good (especially for zinc deficiency)
  • Safety: High at 15-25mg/day; caution at >40mg/day long-term
  • Timing: Start within 24 hours of symptom onset

For city dwellers : Stress and high physical activity increase the need for zinc. At the same time, the diet is often nutrient-poor (fast food, little meat, and processed foods). Zinc is useful as a preventative basic supplement or at the first signs of a cold.


Source: Science M et al. Zinc for the treatment of the common cold. CMAJ. 2012.

4. Echinacea – plant extract that reduces the risk factor

Echinacea (purple coneflower) is a medicinal plant traditionally used to treat colds. Its active ingredients are complex plant compounds—primarily polysaccharides, alkamides, and caffeic acid derivatives.

Scientific evidence : Meta-analyses show that echinacea can reduce the risk of colds by about 58% and shorten their duration by 1-2 days.[13] However, there is a major problem: the quality and standardization of the preparations vary enormously. Studies with standardized extracts show more consistent results than those with unstandardized products.

How it works : Echinacea has an immunomodulatory effect. It stimulates the production of interferons (antiviral signaling molecules), promotes phagocytosis, and regulates inflammatory cytokines. Animal and cell studies show antiviral effects against various respiratory viruses.

Important note : Echinacea has been studied primarily for short-term use—typically a few weeks during peak respiratory infection season or at the onset of symptoms. Long-term use over many months is less well documented.

Concrete advantages:

  • Modulation of the innate immune system
  • Promotes phagocytosis (immune cells “eat” pathogens more effectively)
  • Potential antiviral effects 1-2 days shorter cold duration in some studies

Classification:

  • Evidence level: Good for standardized extracts, variable overall
  • Safety: High for short-term use (a few weeks); caution in autoimmune diseases
  • Relevance: People with frequent colds, for seasonal use

For city dwellers : In the city, you're constantly exposed to viruses—on the subway, in offices, at the gym. Echinacea can be a useful support during periods of increased risk of infection. Look for standardized extracts with validated levels of active ingredients.

Source : Shah SA et al. Echinacea for preventing and treating the common cold. Cochrane Database Syst Rev. 2014.

5. Elderberry – Promising antiviral plant power

Elderberry (Sambucus nigra) is the dark purple fruit of the black elderberry plant. Its intense color comes from anthocyanins—potent antioxidants with immune-modulating properties.

Scientific evidence : The available data is still quantitatively limited, but the available studies show impressive results. A meta-analysis of four randomized controlled trials with 180 participants showed significant reductions in symptom duration in viral respiratory infections[14].

Two studies are particularly noteworthy:

  • Air travelers (Tiralongo 2016): 312 long-haul travelers. The elderberry group had 57 cumulative sick days compared to 117 in the placebo group—a 51% reduction.
  • Influenza patients (Zakay-Rones 2004): 60 flu patients. The elderberry group was symptom-free after an average of 3.1 days, while the placebo group was symptom-free after 7.1 days.

How it works : Laboratory studies show that elderberry can inhibit the binding of influenza viruses to cells—a direct antiviral effect. At the same time, it modulates the production of cytokines (IL-6, IL-8, TNF-alpha), which dampens excessive inflammatory reactions.

Concrete advantages:

  • Antiviral effect against influenza and other respiratory viruses
  • Immunomodulation through cytokine regulation
  • Up to 50% shorter symptom duration in studies
  • Strong antioxidant capacity through anthocyanins

Classification:

  • Evidence level: promising to good
  • Safety: Very high for processed/heated berries (do not consume raw berries)
  • Relevance: People with frequent viral infections, frequent travelers, preventive use

Limitation : Almost all studies come from the same research groups. More independent replications would be desirable to confirm the results.

For city dwellers : If you're on the move a lot—for work or commuting—your risk of infection is constantly elevated. Elderberry can help prepare your immune system for this constant viral exposure. It's effective both as a preventative measure and during an existing infection.

Source : Hawkins J et al. Black elderberry supplementation effectively treats upper respiratory symptoms. Complement Ther Med. 2019.

The interaction: measures + ingredients

The measures form the foundation – the ingredients are the targeted reinforcement. Think of it like building a house: exercise, sleep, and stress management are the load-bearing walls. Vitamin D, zinc, and the herbal extracts are like additional insulation – they make the house more robust, but without a solid foundation, they're useless.

In practice this means –

Phase 1 (September/October):

Establish the 5 measures. Build routines that fit your daily routine. This is the most important investment.

Phase 2 (October to March):

Supplement specifically with the 5 ingredients, especially during high-risk periods: the first wave of colds in the office, a lot of travel, stressful project phases.

Phase 3 (April to August):

Specific supplementation to strengthen the immune system can be reduced again, but maintain the measures.

Title

Common Immune Prep Mistakes (and How to Avoid Them)

Mistake 1: Wanting to change everything at once

The problem: You start out highly motivated and want to exercise every day, take cold showers, sleep perfectly, meditate, and take 10 supplements. After a week, you're exhausted and give up.


The solution: Build gradually. One new habit per week is more than enough. Long-term behavior change takes time. Start with what will have the greatest impact: optimizing sleep. Then integrate exercise. Then stress management. Supplements come last.

Mistake 2: Supplements as a substitute for good habits

The problem: You think a vitamin D capsule will compensate for the fact that you only sleep 5 hours a night or never exercise.

The solution: Always prioritize the basics. No capsule can compensate for poor sleep, chronic stress, or lack of exercise. Supplements are a reinforcement, not a replacement.

Mistake 3: Impatience and unrealistic expectations

The problem: After three days, you expect to never get sick again. When you first get a cold, you think, "It won't work anyway."


The solution: Immune strengthening is a marathon, not a sprint. The effects become apparent over weeks and months—not after three days. The relevant comparison: Are you sick less often or for shorter periods this winter than last year? That's the benchmark.

Mistake 4: Either-or thinking

The problem: You either do everything perfectly or nothing at all. A missed workout means, "Oh, it doesn't matter anyway."


The solution: Perfection isn't the goal, consistency is. 80% success over 6 months far exceeds 100% success over 2 weeks. It's better to exercise 3 times a week than not at all because you can't manage 5 times.

Mistake 5: Ignoring individual factors

The problem: You blindly copy what works for others without listening to your own body.

The solution: Test, observe, and adapt. Some people need 9 hours of sleep, others 7.5. Some benefit greatly from cold showers, others don't. Find out what works for you—not what studies show works on average.

Title

Your 4-week implementation plan

Theory is important, implementation is everything. Here's a structured plan to help you systematically build your personal immune prep protocol:

Week 1: Foundation – Sleep and Hydration

Focus : Establish the two most important basic measures

To do:

  • Set a fixed bedtime (calculate 7-9 hours back from your wake-up time)
  • Buy a humidifier for your bedroom (budget: €30-80)
  • Set three water reminders on your phone (10 a.m., 2 p.m., 6 p.m.)
  • Track your sleep hours – use an app or a simple notebook

Success criterion : At the end of the week, you should have achieved your target sleep duration 5 out of 7 nights and drink at least 2 liters per day.

Week 2: Movement – ​​Integrating Movement

Focus : Make regular exercise a routine

To do:

  • Plan 4 exercise sessions of 30-45 minutes each per week (enter them as fixed appointments in your calendar)
  • Try different activities – find out what you enjoy (jogging, cycling, strength training, swimming, dancing)
  • Start with moderate intensity (better too easy than too hard – you should still be able to hold a conversation)
  • At least one unit should take place outside (daylight bonus)

Success criterion : Completed 4 exercise units and found an activity that suits you.

Week 3: Cold & Stress – Hardening and Relaxation

Focus : Start cold training and stress management

To do:

  • Start with 30 seconds of cold water at the end of the shower (daily)
  • Establish a 10-minute relaxation routine (morning OR evening – not both if it’s too much)
  • Try different techniques: Meditation (e.g. Headspace, Calm), 4-7-8 breathing, Yoga (e.g. YouTube)
  • Keep a short stress diary: When do you feel stressed? What helps you?

Success criteria : Took a cold shower 5 out of 7 days and found a relaxation technique that suits you.

Week 4: Integration & Supplementation

Focus : Combine all measures + add ingredients
To do:

  • Maintain all habits from weeks 1-3 (as best as possible – 80% is perfectly fine)
  • Start with supplementation (e.g. immune support or individual ingredients)
  • Evaluate: What's working well? Where do you still need adjustments?
  • Plan long-term: How can you do this sustainably throughout the winter? What's realistic?

Success criterion : You have established your personal immune prep protocol, which you can maintain for the next few months – even if it is not perfect.

The most important thing at the end:
You have more control than you think

The idea that colds just "happen" in winter and there's nothing we can do about it is false. Yes, viruses are everywhere. Yes, the weather is getting colder. Yes, the days are getting shorter. But your body is an adaptable system that—if you support it properly—can be amazingly resilient.

The 5 steps and 5 ingredients in this article aren't a secret recipe. They're applied science, consistently implemented. No magic, no miracles—just proven strategies that work when you apply them over the long term.

You don't have to be perfect. 80% implementation over 6 months is worth more than 100% implementation over 2 weeks. You don't have to take cold showers every day, meditate every day, or sleep perfectly every day. But the direction has to be right, and consistency makes all the difference.

While others struggle through cold season, you can stay strong, energetic, and healthy—not by luck, but by being proactive. You have the tools now. Now it's up to you to use them.

This winter will be different.

Important NOTE

This article is for informational purposes only and does not replace medical advice. If you have any health concerns or are unsure about supplementation, please consult a physician or nutritionist. The effectiveness of dietary supplements may vary from individual to individual.

Sources

Measures:
[1] Nieman, DC, & Wentz, L.M. (2019). The compelling link between physical activity and the body's defense system. Journal of Sport and Health Science , 8(3), 201-217.
[2] Buijze, GA, et al. (2016). The Effect of Cold Showering on Health and Work: A Randomized Controlled Trial. PLoS ONE , 11(9), e0161749.
[3] Irwin, M., et al. (1996). Partial night sleep deprivation reduces natural killer and cellular immune responses in humans. The FASEB Journal , 10(5), 643-653.
[4] Kudo, E., et al. (2019). Low ambient humidity impairs barrier function and innate resistance against influenza infection. Proceedings of the National Academy of Sciences , 116(22), 10905-10910.
[5] Black, DS, & Slavich, GM (2016). Mindfulness meditation and the immune system: a systematic review of randomized controlled trials. Annals of the New York Academy of Sciences , 1373(1), 13-24.

Ingredients:
[6] Hemilä, H., & Chalker, E. (2013). Vitamin C for preventing and treating the common cold. Cochrane Database of Systematic Reviews , (1), CD000980.
[7] Carr, AC, & Maggini, S. (2017). Vitamin C and Immune Function. Nutrients , 9(11), 1211.
[8] Martineau, AR, et al. (2017). Vitamin D supplementation to prevent acute respiratory tract infections: systematic review and meta-analysis of individual participant data. BMJ , 356, i6583.
[9] Jolliffe, DA, et al. (2021). Vitamin D supplementation to prevent acute respiratory infections: a systematic review and meta-analysis of aggregate data from randomized controlled trials. The Lancet Diabetes & Endocrinology , 9(5), 276-292.
[10] Aglipay, M., et al. (2017). Effect of High-Dose vs Standard-Dose Wintertime Vitamin D Supplementation on Viral Upper Respiratory Tract Infections in Young Healthy Children. JAMA , 318(3), 245-254.
[11] Science, M., et al. (2012). Zinc for the treatment of the common cold: a systematic review and meta-analysis of randomized controlled trials. Canadian Medical Association Journal , 184(10), E551-E561.
[12] Hemilä, H. (2017). Zinc lozenges and the common cold: a meta-analysis comparing zinc acetate and zinc gluconate, and the role of zinc dosage. JRSM Open , 8(5).
[13] Shah, SA, et al. (2007). Evaluation of echinacea for the prevention and treatment of the common cold: a meta-analysis. The Lancet Infectious Diseases , 7(7), 473-480.
[14] Hawkins, J., et al. (2019). Black elderberry (Sambucus nigra) supplementation effectively treats upper respiratory symptoms: A meta-analysis of randomized, controlled clinical trials. Complementary Therapies in Medicine , 42, 361-365.
[15] Tiralongo, E., et al. (2016). Elderberry Supplementation Reduces Cold Duration and Symptoms in Air-Travellers: A Randomized, Double-Blind Placebo-Controlled Clinical Trial. Nutrients , 8(4), 182.

Additional studies:

Cohen, S., et al. (2009). Sleep habits and susceptibility to the common cold. Archives of Internal Medicine , 169(1), 62-67.

Prather, AA, et al. (2015). Behaviorally Assessed Sleep and Susceptibility to the Common Cold. Sleep , 38(9), 1353-1359.

Cohen, S., et al. (1991). Psychological stress and susceptibility to the common cold. New England Journal of Medicine , 325(9), 606-612.

Segerstrom, SC, & Miller, GE (2004). Psychological stress and the human immune system: a meta-analytic study of 30 years of inquiry. Psychological Bulletin , 130(4), 601.