Introduction
By Performance Nutritionist, Tamara Walker. Book a 1-2-1 with Tam here. Winter is upon us, bringing with it colder temperatures and more time spent indoors. This season also marks a rise in circulating viruses, making young athletes particularly vulnerable to the seasonal flu. Even a brief illness can significantly impact an athlete’s strength, stamina, motivation, and overall performance. Therefore, understanding the intricacies of the immune system, the role of nutrition in its support, and the timing of a return to training is crucial in helping athletes remain healthy and bounce back stronger.
Why Winter Increases Illness Risk
Flu viruses thrive in cold and dry air, spreading more easily when people gather indoors for training, matches, and travel scenarios like minibuses or changing rooms (1). In these close-contact environments, germs can be transmitted through the air and surfaces, facilitating the spread of infections. Additionally, reduced winter sunlight may decrease vitamin D levels, which play a critical role in immune regulation, thereby increasing vulnerability to respiratory infections (2). The cold air can also dry out the airways, weakening natural barriers that typically prevent viruses from entering the body.
What Happens to Your Body When You Are Sick
Innate Immune System: Rapid Defence
The innate immune system kicks into action immediately when the flu virus invades the body. Its defense mechanisms include:
- Fever to increase body temperature and slow viral replication (3)
- Inflammation leading to fatigue and muscle soreness
- Enhanced mucus production to trap viral particles
- Activation of white blood cells to attack infected cells
These symptoms manifest swiftly, indicating that the body is actively combating the infection.
Adaptive Immune System: Targeted Defence
The adaptive immune system crafts a more precise response:
- B cells produce antibodies specifically targeting the influenza virus (4)
- T cells destroy infected cells, reducing viral load
- Memory cells form to facilitate quicker responses in future infections
Significant energy is allocated to these processes, often resulting in decreased strength, reduced endurance, and slower decision-making among athletes during illness (3).
Nutrition for Strong Immunity
Adequate Energy Intake
Young athletes frequently face challenges in consuming sufficient energy during hectic school and training schedules. Low energy availability elevates stress hormones and suppresses immune function (2). Regular meals and meeting energy requirements are essential, particularly during intensive training and illness periods.
Key Immune Nutrients
Several nutrients are vital for supporting immune cell function, including:
- Vitamin C (found in berries, peppers, and citrus fruits)
- Vitamin D (from oily fish, fortified foods, and sunlight exposure) (2)
- Zinc (present in meat, seeds, and nuts)
- Protein (crucial for immune cell growth and repair)
- Omega-3 fats (from sources like salmon, walnuts, and chia seeds) which help regulate inflammation
Hydration Is Essential
Fever and increased breathing rates can lead to a greater loss of fluids. Even mild dehydration may slow recovery and exacerbate fatigue (1). Drinking warm liquids such as soups or herbal teas can aid hydration and soothe a sore throat. A slight drop in hydration can also impair concentration and decision-making, which are critical for safe training and performance.
Support Gut Health
A properly nourished gut microbiome is essential for immune regulation and inflammation control. A healthy gut fosters a stable immune response and can help athletes better cope during the winter months (2). Beneficial foods include:
- Yoghurt or kefir
- Fermented vegetables like sauerkraut and kombucha
- High-fibre whole grains and fruits
Sleep: The Ultimate Immune Booster
Sleep enhances immune function by supporting antibody production and modulating immune signaling. Poor sleep is associated with an increased risk of respiratory infections and prolonged recovery (5). Young athletes should aim for 8 to 10 hours of sleep per night, with additional rest when unwell. Adequate sleep also boosts focus, reaction time, and movement coordination, which may decline during illness.
Return to Play: When Is It Safe?
Resuming play too soon can prolong illness, heighten injury risk, and worsen overall fatigue. Sports medicine guidelines provide clear recommendations (6).
The Neck Rule
- Above-the-neck symptoms (such as a runny nose, mild headache, or sore throat): Light activity may be permissible.
- Below-the-neck symptoms (including fever, chest congestion, deep cough, and body aches): Training should be avoided.
Fever Requires Complete Rest
Athletes should be fever-free for at least 24 hours without medication before resuming exercise (6).
Gradual Return to Play Progression
- Light activity: Walking or gentle cycling
- Low-intensity training: Relaxed aerobic exercise
- Moderate sport skills: Technical drills, non-contact
- Full training: Normal sessions
- Competition: Only once entirely symptom-free
If symptoms worsen at any stage, athletes should revert to the previous level.
Protecting Team Mates
Preventive measures help protect both individual athletes and the entire team (1). Recommended practices include:
- Regular handwashing
- Avoiding shared bottles and towels
- Covering coughs and sneezes
- Staying home when ill
- Cleaning shared equipment
Conclusion
The winter flu season presents heightened risks for young athletes due to colder weather, reduced sunlight, and increased indoor time. When athletes fall ill, the body prioritizes fighting the infection, which can drain energy, strength, and performance. Adequate nutrition, hydration, gut health support, and sufficient sleep are fundamental to maintaining a robust immune system. Returning to training should be gradual and only proceed after symptoms have improved, with fever-free rest being a non-negotiable step. Practicing good hygiene not only safeguards the athlete but also the entire team from the spread of germs.
By Performance Nutritionist, Tamara Walker. Book a 1-2-1 with Tam here.
Disclaimer: This article provides general information on nutrition for youth athletes and is not a substitute for professional dietary advice or individual nutritional counseling. Every child’s nutritional needs may vary based on factors such as age, size, physical activity level, and medical conditions. We strongly advise consulting a registered dietitian or healthcare provider before making any dietary changes, including the addition of food powders. YSN and the author do not hold responsibility for any potential consequences from any treatment, procedure, dietary modification, action, or medication application resulting from reading or following the information in this article.
References
- Centers for Disease Control and Prevention. How flu spreads. Atlanta: CDC; 2024.
- Calder PC. Nutrition and immunity: lessons for athletes. Sports Med. 2020;50(1):1–10.
- Gleeson M. Immune function in sport and exercise. J Appl Physiol. 2007;103(2):693–9.
- Walsh NP, Gleeson M, Pyne DB, Nieman DC, Dhabhar FS, Shephard RJ, et al. Position statement: Part one. Immune function and exercise. Exerc Immunol Rev. 2011;17:6–63.
- Irwin MR. Sleep and inflammation: partners in sickness and in health. Nat Rev Immunol. 2019;19(11):702–15.
- American College of Sports Medicine. Illness and exercise: return to play guidance. Indianapolis: ACSM; 2023.
