The immune system is a highly sophisticated network of white blood cells, antibodies, cytokines, lymphatic tissues and signalling molecules that protects the body against pathogens while maintaining internal balance, or homeostasis (Calder, 2020). Its function is influenced not only by genetics but also by lifestyle behaviours, environmental exposures and psychosocial factors. Contemporary immunology and public health research consistently demonstrate that immune competence is shaped by nutrition, physical activity, sleep quality, stress levels, body composition, substance use, hygiene practices and vaccination status (Nieman and Wentz, 2019; WHO, 2020). Rather than relying on a single “immune-boosting” solution, strengthening immunity requires an integrated and sustained lifestyle approach.
1.0 Healthy Diet: Fuel for Immune Defence
A balanced, nutrient-dense diet provides the vitamins, minerals and bioactive compounds necessary for immune cell production and regulation. Micronutrients such as vitamin C, vitamin D, zinc, selenium, iron and vitamin A play critical roles in immune cell signalling and antibody production (Calder et al., 2020).
Diets rich in:
- Fruits and vegetables
- Whole grains
- Legumes and beans
- Lean proteins
- Healthy fats (e.g., olive oil, nuts, oily fish)
have been associated with lower systemic inflammation and improved immune responses (Calder, 2020).
For example, vitamin C contributes to the function of phagocytes and supports epithelial barrier integrity, while zinc is essential for T-cell development. Conversely, highly processed diets high in saturated fats and refined sugars can promote chronic inflammation and impair immune regulation.
The Mediterranean dietary pattern is frequently cited as supportive of immune resilience due to its emphasis on plant-based foods and unsaturated fats (Calder et al., 2020).
2.0 Regular Exercise: Enhancing Immune Surveillance
Moderate, consistent physical activity enhances immune surveillance, improves circulation of immune cells and reduces chronic inflammation (Nieman and Wentz, 2019). Exercise increases the recirculation of natural killer (NK) cells and T lymphocytes, which play key roles in detecting pathogens.
The World Health Organization (2020) recommends at least 150 minutes of moderate-intensity physical activity per week for adults.
Examples of beneficial activities include:
- Brisk walking
- Cycling
- Swimming
- Strength training
However, excessive high-intensity training without adequate recovery may temporarily suppress immune function — a phenomenon observed in endurance athletes (Nieman, 1994). For most individuals, moderate exercise strengthens immunity rather than weakens it.
3.0 Adequate Sleep: The Foundation of Immune Repair
Sleep is not passive rest; it is an active period of immune regulation. During sleep, the body produces cytokines, proteins that help regulate immune responses (Irwin, 2015).
Research shows that individuals who sleep fewer than seven hours per night are more susceptible to infections (Cohen et al., 2009). Sleep deprivation reduces antibody responses and impairs inflammatory regulation.
Adults should aim for 7–9 hours of quality sleep per night. Maintaining a consistent sleep routine, limiting screen exposure before bed and ensuring a cool, dark bedroom environment are evidence-based strategies for improving sleep hygiene (NHS, 2022).
4.0 Stress Management: Protecting Immune Balance
Short-term stress activates the fight-or-flight response, releasing hormones such as cortisol and adrenaline (McEwen, 2007). While acute stress can temporarily enhance certain immune responses, chronic stress suppresses immune cell function and increases inflammatory activity (Segerstrom and Miller, 2004).
Cohen et al. (1991) demonstrated that individuals experiencing higher psychological stress were significantly more likely to develop the common cold when exposed to a virus.
Effective stress management techniques include:
- Mindfulness meditation
- Deep breathing exercises
- Yoga
- Social support
- Regular physical activity
Reducing chronic stress helps restore immune regulation and resilience.
5.0 Hydration: Supporting Physiological Function
Adequate hydration supports circulation, lymphatic flow and cellular metabolism. While water itself does not directly “boost” immunity, dehydration can impair mucosal barriers — the body’s first line of defence against pathogens.
Maintaining regular fluid intake throughout the day supports overall physiological balance and optimal immune function.
6.0 Limiting Alcohol and Avoiding Smoking
Excessive alcohol consumption impairs immune cell communication and increases susceptibility to infections, particularly respiratory illnesses (Szabo and Saha, 2015).
Smoking damages the respiratory epithelium and weakens mucociliary clearance, increasing infection risk (WHO, 2020).
Reducing alcohol intake to recommended limits (no more than 14 units per week in the UK) and stopping smoking significantly improve immune and respiratory health.
7.0 Maintaining a Healthy Weight
Obesity is associated with chronic low-grade inflammation and impaired immune responses (Calder et al., 2020). Excess adipose tissue produces pro-inflammatory cytokines that disrupt immune balance.
Maintaining a healthy body weight through balanced nutrition and regular exercise supports metabolic and immune function.
For example, individuals with obesity are at increased risk of severe complications from viral infections, including influenza and COVID-19.
8.0 Practising Good Hygiene
Basic hygiene practices remain among the most effective infection prevention strategies.
These include:
- Regular handwashing with soap and water
- Avoiding touching the face with unwashed hands
- Proper respiratory etiquette (covering coughs and sneezes)
Hygiene reduces pathogen exposure and decreases infection transmission rates.
9.0 Vaccinations: Supporting Adaptive Immunity
Vaccines stimulate the immune system to produce memory cells and antibodies without causing disease. This enables rapid and effective responses upon future exposure (WHO, 2020).
Vaccination remains one of the most powerful public health tools for preventing infectious disease.
Staying up to date with recommended vaccinations protects both individual and community health.
10.0 Supplements: Evidence and Caution
Certain supplements — including vitamin C, vitamin D and zinc — may support immune function in individuals with deficiencies (Calder et al., 2020).
Vitamin D, in particular, plays a role in immune modulation, and deficiency has been linked to increased infection risk.
However, supplementation should not replace a balanced diet. Excessive intake of certain nutrients may be harmful. Consultation with a healthcare professional is recommended before beginning any supplement regimen.
An Integrated Approach to Immune Health
The immune system does not operate in isolation. It interacts with:
- The endocrine system
- The nervous system
- The metabolic system
This interconnectedness means that improving immunity requires a holistic lifestyle strategy rather than reliance on a single intervention.
The World Health Organization (2020) defines health as a state of complete physical, mental and social well-being. Immune resilience reflects this integrated model.
Improving your immune system involves consistent attention to:
- Balanced nutrition
- Regular moderate exercise
- Adequate sleep
- Stress management
- Hydration
- Healthy weight maintenance
- Limiting alcohol and avoiding smoking
- Good hygiene practices
- Vaccination adherence
There is no instant immune “boost”. Instead, long-term resilience emerges from sustained, evidence-based habits.
Small, daily choices accumulate into measurable physiological benefits. By prioritising sleep, nourishing food, movement and emotional well-being, individuals can strengthen their immune defences and protect long-term health.
References
Calder, P.C. (2020) ‘Nutrition, immunity and COVID-19’, BMJ Nutrition, Prevention & Health, 3(1), pp. 74–92.
Calder, P.C. et al. (2020) ‘Optimal nutritional status for a well-functioning immune system’, Nutrients, 12(4), pp. 1–25.
Cohen, S., Tyrrell, D.A.J. and Smith, A.P. (1991) ‘Psychological stress and susceptibility to the common cold’, New England Journal of Medicine, 325(9), pp. 606–612.
Cohen, S. et al. (2009) ‘Sleep habits and susceptibility to the common cold’, Archives of Internal Medicine, 169(1), pp. 62–67.
Irwin, M.R. (2015) ‘Why sleep is important for health: a psychoneuroimmunology perspective’, Annual Review of Psychology, 66, pp. 143–172.
McEwen, B.S. (2007) ‘Physiology and neurobiology of stress and adaptation’, Physiological Reviews, 87(3), pp. 873–904.
NHS (2022) Sleep and stress management. Available at: https://www.nhs.uk.
Nieman, D.C. (1994) ‘Exercise, infection and immunity’, International Journal of Sports Medicine, 15(S3), pp. S131–S141.
Nieman, D.C. and Wentz, L.M. (2019) ‘The compelling link between physical activity and the body’s defence system’, Journal of Sport and Health Science, 8(3), pp. 201–217.
Segerstrom, S.C. and Miller, G.E. (2004) ‘Psychological stress and the human immune system’, Psychological Bulletin, 130(4), pp. 601–630.
Szabo, G. and Saha, B. (2015) ‘Alcohol’s effect on host defence’, Alcohol Research, 37(2), pp. 159–170.
World Health Organization (2020) Vaccination and immune protection. Geneva: WHO.
