When winter arrives, the combination of dark mornings, cold air, and heavy training blocks can test even the most disciplined athlete. Consistency is often the difference between progress and plateau, yet illness can easily derail momentum. This is where nutrition to strengthen immunity becomes an essential part of any athlete’s performance strategy. Beyond fuelling muscles, smart nutrition supports the body’s natural defences, reducing time lost to colds, fatigue, and disrupted recovery.
Why Winter Health Matters for Athletes
Winter places unique stress on an athlete’s body. Cold, dry air irritates the airways, while indoor environments increase exposure to germs. Training loads often remain high, but appetite and energy intake can drop. Add darker days, disrupted sleep, and reduced sunlight exposure, and you have a perfect storm for weakened immunity.
Upper respiratory symptoms are the most common illness among athletes during the colder months, accounting for up to 65% of reported illnesses [4]. These episodes may seem minor but can cost several days of training and reduce performance for weeks afterwards.
Understanding why illness risk rises in winter is the first step. The second is using nutrition to strengthen immunity so the body has the resources to stay resilient under pressure.
Energy Availability: The Foundation of Immune Defence
One of the most common but overlooked causes of frequent illness in athletes is low energy availability. When the body doesn’t receive enough calories to support both exercise and normal physiological function, immune defences suffer. This state, often linked with Relative Energy Deficiency in Sport (RED-S), can reduce the production of immune cells and antibodies, making athletes more susceptible to infections [7].
Maintaining sufficient daily energy intake is critical for immune health. Carbohydrates play a particularly protective role. During intense training, consuming carbohydrate before, during, and after exercise helps regulate stress hormones and maintain white blood cell activity [7].
For winter training blocks, that means planning meals and snacks to match energy output. If appetite drops, athletes can use more compact fuel sources—porridge with honey, smoothies, dried fruit, or recovery shakes, to stay on top of intake. In this way, nutrition to strengthen immunity begins with the fundamentals: meeting energy needs consistently.
Carbohydrate Availability and Immune Protection
Carbohydrate timing and availability are central to maintaining a robust immune system during heavy training phases. When muscle glycogen stores are low, the body releases higher levels of stress hormones such as cortisol and adrenaline, which can suppress immune function [3].
During prolonged or high-intensity sessions, athletes who fail to consume carbohydrate experience larger increases in inflammatory cytokines, including interleukin-6 (IL-6), and a greater fall in salivary immunoglobulin A (IgA), a key component of mucosal immunity [5, 3].
In contrast, consuming 30–60 grams of carbohydrate per hour during training maintains blood glucose, reduces cortisol, and limits immune suppression [7]. Post-exercise carbohydrate ingestion, especially when paired with protein, accelerates glycogen restoration and supports the recovery of immune cells [6].
This principle of carbohydrate availability extends beyond single sessions. Athletes who chronically under-fuel or regularly train fasted may experience prolonged immune stress and higher illness risk. Daily carbohydrate intake should align with training intensity:
- High-intensity days: 6–10 g carbohydrate/kg body weight
- Low or recovery days: 3–5 g carbohydrate/kg body weight
Supporting carbohydrate availability is therefore a cornerstone of nutrition to strengthen immunity, ensuring the immune system stays active rather than suppressed by chronic energy stress.
Vitamin D: The Winter Immunity Safeguard
Among all micronutrients, vitamin D deserves its own spotlight during the colder months. Known for its crucial role in bone strength, it also regulates immune cell activity and helps to control inflammation.
From October to March in the UK, sunlight is too weak for the skin to produce enough vitamin D. As a result, deficiency is common, especially in athletes who train indoors or cover up outdoors. Low vitamin D status has been repeatedly linked with higher rates of respiratory illness and slower recovery from infection [2].
UK public health guidelines recommend 400 IU (10 µg) per day, yet it’s almost impossible to achieve this amount through food alone. Oily fish, eggs, and fortified dairy or plant milks contribute small amounts, but not enough to maintain healthy blood levels through winter.
For most athletes, a daily supplement of 1,000–2,000 IU (25–50 µg) is considered safe and effective for maintaining optimal status. Higher doses can be used short-term under professional supervision when deficiency is confirmed, but routine megadoses aren’t necessary.
For the most accurate and personalised approach, it’s best to check your vitamin D status with a blood test, particularly if you have a history of stress fractures, frequent illness, or persistent fatigue. Test results guide dosage precisely and help avoid both deficiency and unnecessary excess.
Maintaining adequate vitamin D through the winter is a simple, evidence-based way to support immune defence and enhance recovery. Think of it as one of the easiest wins in your broader strategy for nutrition to strengthen immunity.
Micronutrients That Support Immune Function
Beyond vitamin D, other vitamins and minerals fine-tune immune resilience by supporting cell growth, antioxidant defence, and inflammation control.
- Vitamin C supports white blood cell production and antioxidant protection.
- Vitamins E and A help regulate immune signalling.
- Iron, zinc, and selenium aid in the formation of immune proteins and enzymes.
- B vitamins, particularly B6 and B12, support energy metabolism and immune cell function.
Athletes should focus on a food-first approach. Oily fish, eggs, dairy, lean meats, fortified cereals, citrus fruits, leafy greens, and nuts provide a strong micronutrient base. Supplementation should only fill confirmed gaps identified through diet analysis or blood testing.
The Gut–Immune Connection
Over 70 percent of the immune system resides in the gut. The gut microbiota, our community of beneficial bacteria, acts as the first line of defence against pathogens. A healthy gut helps train immune cells, reduce inflammation, and maintain mucosal barriers in the respiratory tract.
Athletes with greater microbial diversity tend to experience fewer upper respiratory symptoms [1]. Training stress, poor diet, and low fibre intake can disrupt this balance, making probiotic and prebiotic foods valuable during winter.
Daily options include live yoghurt, kefir, sauerkraut, kimchi, miso, and fibre-rich foods like oats, beans, and bananas. These help maintain a robust gut ecosystem and, in turn, enhance immune function. Supporting gut health is one of the simplest ways to apply nutrition to strengthen immunity during demanding training periods.
Hydration, Sleep, and Recovery Nutrition
Hydration plays an underrated role in winter immunity. Cold air can be deceptively dehydrating as athletes may not feel thirsty. Even mild dehydration dries out mucous membranes in the airways, making it easier for pathogens to enter. Drinking water regularly and including electrolytes in longer sessions helps maintain hydration and mucosal defence.
Sleep is another powerful immune ally. Poor or inconsistent sleep reduces natural killer cell activity, slowing recovery and increasing illness risk. Most adults need seven to nine hours of quality sleep per night, but athletes often benefit from eight to ten hours, including naps, to fully support training adaptation and immune function. Nutritionally, athletes can support sleep by consuming a small meal rich in carbohydrates and protein around four hours before bed, as this combination may shorten sleep onset and enhance recovery [8, 9]. Examples include yoghurt with oats, or wholegrain toast with nut butter and banana.xamples include yoghurt with oats, or wholegrain toast with nut butter and banana. A
Tart cherry juice has also been shown to improve sleep quality and reduce inflammation through its natural melatonin and antioxidant compounds [10, 11]. While current evidence does not confirm that it blunts training adaptations, it should be used strategically. The best approach is to include it after particularly hard sessions, during competition phases, or when sleep is compromised, rather than as a daily supplement.
When combined, hydration, adequate sleep, and balanced evening nutrition form part of a holistic nutrition to strengthen immunity approach.
When Illness Strikes: Fuelling Recovery
Despite best efforts, illness sometimes happens. When it does, smart nutrition can shorten recovery and protect lean mass. Appetite may fall, but it’s important to maintain energy intake through softer, easy-to-digest foods such as soups, smoothies, or porridge. Protein intake should remain consistent, about 20–25 g every few hours, to support immune cell repair and prevent muscle loss.
Hydration is critical during fever or congestion, and including sodium in fluids can improve absorption. Focus on fruits, vegetables, and colourful foods to provide natural antioxidants without over-supplementing. Excessive antioxidant pills can blunt the body’s adaptive responses, while whole foods provide a balanced, effective source.
When cold symptoms appear, small, targeted nutrition strategies may help recovery. Evidence suggests that daily vitamin C supplementation of 250–500 mg can reduce illness risk in athletes exposed to heavy training loads [12]. Higher doses (up to 1 g/day) are sometimes used short-term during acute symptoms, but there is little additional benefit beyond 500 mg/day, and sustained high intakes can cause gastrointestinal discomfort.
During illness, zinc lozenges providing a total of 75–95 mg elemental zinc per day may shorten symptom duration if started early, ideally within the first two days [13, 14]. Lozenges should be taken every two to three hours while awake and limited to a maximum of 5–7 days, as prolonged use or very high doses can interfere with copper absorption and cause nausea or metallic taste. Nasal zinc products are not recommended due to risk of smell loss.
Both should be used alongside the core recovery principles, sufficient energy, hydration, and rest, rather than as substitutes for them.
Practical Winter Nutrition Checklist for Athletes – The Big Rocks
Meet your energy needs.
Consistent fuelling supports immune cell production and recovery. Under-fuelling is one of the quickest ways to weaken immune defences and increase illness risk.
Maintain carbohydrate availability and smart fuelling.
Include carbohydrate before, during, and after training to reduce stress hormones and support immune function. Aim for 30–60 g per hour during longer sessions and refuel promptly afterwards.
Stay hydrated.
Cold weather can blunt thirst, increasing the risk of dehydration. Sip fluids regularly, replace sweat losses after training, and use electrolytes during longer or high-intensity sessions.
Support gut health.
A diverse gut microbiome strengthens immune defences. Include probiotic and prebiotic foods daily such as Probiotics Drinks, live yoghurt, kefir, oats, beans, or fermented vegetables.
Monitor vitamin D through the winter.
UK guidelines recommend 400 IU (10 µg) per day, but 1,000–2,000 IU (25–50 µg) is safe for most athletes. For personalised guidance, check your vitamin D status with a blood test.
Prioritise quality sleep.
Aim for eight to ten hours of sleep per night to support recovery and immune resilience. An evening snack of carbohydrate and protein about four hours before bed may help shorten sleep onset.
Include key immune-supporting nutrients.
Focus on foods rich in vitamin C, zinc, and other micronutrients. During illness, use vitamin C (250–500 mg/day) and zinc lozenges (75–95 mg/day for ≤7 days) as short-term support.
Be prepared.
Keep essentials like vitamin D, vitamin C, and zinc lozenges in stock, so you can act quickly when early symptoms appear and avoid missing the recovery window.
Take-Home Message
Athletes often focus on fuelling for performance but overlook the immune system that makes consistent training possible. Nutrition to strengthen immunity is not an add-on, it’s part of the foundation of performance itself. Meeting energy needs, supporting gut health, balancing micronutrients, and sleeping well all work together to keep the body strong.
Illness prevention may not be as exciting as new personal bests, but it’s the hidden factor that keeps progress uninterrupted. If you want to tailor your nutrition plan to your winter training load and personal needs, book a consultation today and stay one step ahead of winter fatigue.
Ready to take your winter training to the next level?
Don’t wait until illness forces a break. A tailored performance nutrition plan can strengthen immunity, support recovery, and keep your training consistent all season long.
Book a consultation today to optimise your winter fuelling, immune health, and recovery strategy.
Reference List
- Colbey C, Cox AJ, Pyne DB, Zhang P, Cripps AW, West NP. Upper respiratory symptoms, gut health and mucosal immunity in athletes. Sports Med. 2018; 48(1): 65–77.
- Crescioli C. Vitamin D, exercise, and immune health in athletes. Nutrients. 2022; 14(19): 4047.
- Gleeson M. Immunological aspects of sport nutrition. Sports Med. 2016; 46(Suppl 1): S29–S38.
- Gleeson M, Pyne DB. Respiratory inflammation and infections in high-performance athletes. Immunol Cell Biol. 2016; 94(2): 124–131.
- Nieman DC. Influence of carbohydrate on the immune response to intensive, prolonged exercise. Exerc Immunol Rev. 1998; 4: 64–76.
- Walsh NP, Gleeson M, Pyne DB, et al. Exercise and the immune system. Compr Physiol. 2011; 1(2): 683–699.
- Walsh NP, et al. Nutrition and athlete immune health: New perspectives on an old paradigm. Eur J Sport Sci. 2019; 19(1): 1–15.
- Halson SL. Sleep in elite athletes and nutritional interventions to enhance sleep. Eur J Sport Sci. 2014; 14(Suppl 1): S123–S130.
- Afaghi A, O’Connor H, Chow CM. High-glycemic-index carbohydrate meals shorten sleep onset. Am J Clin Nutr. 2007; 85(2): 426–430.
- Howatson G, Bell PG, Tallent J, Middleton B, McHugh MP, Ellis J. Influence of tart cherry juice on indices of recovery following marathon running. Scand J Med Sci Sports. 2010; 20(6): 843–852.
- Clifford T, Howatson G, West DJ, Stevenson EJ. The potential benefits of red fruit polyphenols in recovery and performance. Sports Med. 2015; 45(Suppl 1): S139–S148.
- Hemilä H, Chalker E. Vitamin C for preventing and treating the common cold. Cochrane Database Syst Rev. 2013;(1): CD000980.
- Science M, Johnstone J, Roth DE, Guyatt G, Loeb M. Zinc for the treatment of the common cold: a systematic review and meta-analysis of randomized controlled trials. CMAJ. 2012; 184(10): E551–E561.
- Hemilä H. Zinc lozenges and the common cold: a meta-analysis comparing zinc acetate and zinc gluconate. J R Soc Med Open. 2017; 8(5): 2054270417694291.
