Your immune system is one of the most complex and remarkable biological systems in existence. Every single day it identifies and neutralises hundreds of potential threats — bacteria, viruses, fungi and even cancerous cells — without you being consciously aware of it. Yet most of us only think about our immune health when we're already ill, reaching for supplements after the fact rather than building genuine resilience beforehand.
The good news is that there's a solid and growing body of scientific evidence showing that specific lifestyle choices can meaningfully support immune function. These aren't magic bullets or overnight fixes; rather, they're sustainable habits that, over time, make your immune system more capable and more consistent. Here are ten of the most well-supported strategies you can start today.
1. Prioritise Quality Sleep Above Almost Everything Else
If there's one immune-boosting intervention that consistently tops the scientific rankings, it's sleep. Research published in journals including Nature Reviews Immunology has shown that during sleep, your body produces and releases cytokines — proteins that target infection and inflammation. Chronic sleep deprivation (defined as regularly getting fewer than seven hours per night) reduces the production of these protective cytokines and decreases levels of infection-fighting antibodies and cells.
A landmark study by researchers at Carnegie Mellon University found that people who slept fewer than seven hours per night were nearly three times more likely to develop a cold when exposed to a rhinovirus than those who slept eight or more hours. The mechanism appears to involve multiple pathways, including the release of growth hormone during deep sleep stages, which aids cellular repair and the maintenance of immune memory.
Aim for seven to nine hours of sleep per night. Focus on consistency — going to bed and waking at the same time every day, including weekends — as this supports your circadian rhythm, which in turn regulates immune function. Creating a cool, dark, quiet sleep environment and avoiding screens for at least an hour before bed can make a substantial difference.
2. Manage Chronic Stress Through Active Techniques
Short-term acute stress can actually temporarily enhance immune function — it's part of your body's fight-or-flight response. But chronic stress is a different matter entirely. Prolonged stress leads to sustained high levels of cortisol in the bloodstream. Cortisol is anti-inflammatory and suppresses the immune system, which is useful in short bursts but harmful when continuous. Research consistently links chronic stress to reduced natural killer cell activity, lower antibody production, and increased susceptibility to viral infections.
The most evidence-backed stress reduction techniques include mindfulness meditation (even 10–20 minutes a day has been shown to reduce cortisol levels), regular physical exercise, time in nature, meaningful social connection, and journalling. The key is finding what works specifically for you and practising it consistently rather than occasionally. Stress will never be entirely eliminated, but it can absolutely be managed in ways that protect your immune system.
3. Eat a Diet Genuinely Rich in Micronutrients
You've heard "eat more vegetables" so many times it's practically background noise. But the science behind this advice specifically for immune function is compelling. Multiple vitamins and minerals play essential roles in supporting immunity. Vitamin C acts as an antioxidant and supports the production and function of white blood cells. Vitamin D modulates immune responses and its deficiency has been linked to increased susceptibility to infection. Zinc is critical for the development of immune cells and acts as a direct antiviral. Selenium, found in Brazil nuts, seafood and eggs, is essential for proper immune cell function.
The best approach isn't to take high-dose supplements of everything; it's to eat a genuinely varied diet that covers a broad range of micronutrients. Focus on colourful vegetables and fruits (each colour signals different phytonutrients), legumes, whole grains, nuts and seeds, oily fish, and fermented foods. If you have specific deficiencies — vitamin D deficiency is extremely common in the UK, particularly in winter — targeted supplementation based on blood test results is worthwhile.
4. Exercise Regularly, But Don't Overdo It
Regular moderate exercise is one of the most powerful lifestyle medicines available. It improves the circulation of immune cells throughout the body, reduces systemic inflammation, helps regulate stress hormones, and improves the quality and duration of sleep. Research suggests that people who exercise regularly — defined as at least 150 minutes of moderate activity per week — get fewer colds, have shorter illness durations, and mount more effective immune responses to vaccines.
The caveat is important: extremely intense, prolonged exercise — the kind endurance athletes engage in during heavy training periods — can temporarily suppress immune function. This so-called "open window" theory suggests there's a period after prolonged intensive exercise during which athletes are more susceptible to infection. For most people, this isn't relevant; the goal is consistent moderate activity such as brisk walking, cycling, swimming, yoga, or team sports rather than training for ultra-marathons.
5. Stay Well Hydrated
Water plays a multitude of roles in immune function that are easy to underestimate. It's essential for the production of lymph, which carries white blood cells and other immune cells throughout the body. Staying well hydrated keeps the mucous membranes in your nose and throat moist, helping them trap pathogens before they can take hold. Dehydration, even mild, has been shown to impair cognitive function, increase cortisol levels, and reduce the efficiency of cellular processes including those involved in immunity.
Most adults need around 1.5 to 2 litres of water per day from all sources, though this increases with exercise, hot weather, or illness. Don't rely solely on thirst as a guide — it's not a reliable indicator, particularly in older adults. Instead, aim to drink consistently throughout the day, and monitor the colour of your urine: pale straw yellow indicates good hydration; darker yellow suggests you need more fluid.
6. Nurture Your Gut Microbiome
Perhaps the most exciting area of immune research in the past decade has been the gut microbiome — the trillions of microorganisms living in your digestive tract. Approximately 70% of the immune system is located in the gut, and the composition of your microbiome profoundly influences how well it functions. A diverse microbiome with plenty of beneficial bacteria is associated with better immune regulation, lower systemic inflammation, and reduced risk of autoimmune conditions.
To support a healthy microbiome, eat plenty of dietary fibre (the prebiotic that feeds good bacteria), found in vegetables, fruits, whole grains and legumes. Include fermented foods like live yoghurt, kefir, sauerkraut, kimchi, and miso, which introduce beneficial bacteria directly. Limit ultra-processed foods, artificial sweeteners and excessive alcohol, which can disrupt microbial balance. Avoid unnecessary antibiotic use, as antibiotics kill beneficial bacteria along with harmful ones.
7. Don't Smoke, and Limit Alcohol
Smoking is extraordinarily damaging to the immune system across multiple mechanisms. It damages the cilia lining the respiratory tract — the tiny hair-like structures that sweep pathogens away from the lungs. It impairs the function of macrophages (the immune cells that engulf and destroy bacteria), reduces natural killer cell activity, and dramatically elevates the risk of respiratory infections. The good news is that many of these effects begin to reverse within weeks of stopping smoking.
Alcohol, at high levels, suppresses immune function in numerous ways, including impairing the activity of white blood cells and damaging the gut lining, which can allow pathogens to enter the bloodstream. Occasional moderate alcohol consumption (within the UK's recommended guidelines of no more than 14 units per week, spread across several days) has not been shown to significantly impair immune function, but regular heavy drinking definitely does.
8. Maintain a Healthy Body Weight
Both obesity and being significantly underweight can impair immune function, though through different mechanisms. Obesity is associated with chronic low-grade inflammation — a state in which the immune system is continuously activated at a low level, which reduces its ability to mount an acute response when needed. It is also linked to reduced vaccine efficacy and increased severity of infections. Being underweight can mean insufficient stores of key nutrients and reduced production of immune cells due to lack of caloric and protein resources.
For most people, the goal shouldn't be achieving a specific number on the scales, but rather reaching a weight that is comfortable, sustainable, and allows the body to function optimally. This is best achieved through the same fundamentals: a varied whole-foods diet, regular physical activity, adequate sleep and stress management.
9. Spend Time Outdoors and Get Sunlight
Sunlight exposure is one of the primary sources of vitamin D in humans, and vitamin D's role in immune function is well-established. Beyond vitamin D, spending time in nature has been shown to reduce stress hormones, lower blood pressure, and increase natural killer cell activity. Research from Japan on "forest bathing" (Shinrin-yoku) found that spending time among trees significantly increased natural killer cell numbers and activity, effects that lasted for more than 30 days after exposure.
Even simple, regular walks in parks or green spaces can make a meaningful difference. During UK winters, when sunlight exposure is insufficient for vitamin D synthesis, supplementation becomes particularly important. Try to get outside daily, even in winter, and aim for at least 15–20 minutes of midday sunlight on exposed skin (without sunscreen) during summer months, being careful not to burn.
10. Stay Up to Date With Vaccinations
Vaccinations work by training the immune system to recognise and respond to specific pathogens without requiring you to suffer the disease itself. They are among the most effective public health interventions in human history and play a vital role in maintaining a robust immune response to a range of serious diseases. In the UK, the NHS provides a range of vaccinations throughout life, from childhood schedules to annual flu jabs for at-risk groups and Covid-19 boosters.
Keeping up to date with recommended vaccinations isn't just about protecting yourself — it contributes to herd immunity, which protects vulnerable members of the population who cannot be vaccinated for medical reasons. Check your vaccination records, speak with your GP about whether you're up to date, and don't underestimate the importance of this tried-and-tested approach to immune health.
"The immune system is not something you can switch on or off with a single supplement. It's shaped by everything you do — how you sleep, eat, move, and manage stress — over months and years."
A Note on Supplements
The supplement industry generates billions of pounds annually on the promise of immune-boosting products. The reality is more nuanced. Supplements can be genuinely useful when they correct a specific deficiency (vitamin D and zinc being the most commonly deficient nutrients in the UK), but there is little robust evidence that most people benefit from taking high doses of supplements they aren't deficient in. In some cases, excessive supplementation can even be harmful.
Before spending money on supplements, focus on the fundamentals: sleep, nutrition, exercise and stress management. If you suspect specific deficiencies, ask your GP for a blood test rather than self-diagnosing. A well-nourished, well-rested, active body rarely needs additional supplementation beyond vitamin D during the winter months.