Protect your immune system this winter

As cold and flu season arrives, learn how to stay well

• Discover why you’re more prone to colds and flu during the winter months
• Consider diet tweaks to support your immune system
• Why exercise, relaxation and sleep are your friends this winter

While it can seem inevitable you’ll get a cold this winter – adults experience an average of two to three colds per year [1] ­– there are things you can do to help your immune system respond to bacteria and viruses, so that you don’t have to suffer.   

As a kid, you were probably told to wrap up warm to prevent a cold, and recently, researchers uncovered the reason we get more colds and respiratory illnesses in winter – the cold air damages the defence mechanism in the nose [2]. If you’re vulnerable to viruses, you may want to consider wearing a mask as it will help keep your nasal cavity warmer, which will help the immune defence mechanism do its job.

Also keep on top of your vaccinations – you can check if you are eligible for flu and pneumococcal vaccines on the NHS on its website.

Your immunity will be affected by numerous factors, including your diet, exercise, whether you get enough vitamin D, your sleep and stress levels. While you may not be able to completely prevent your exposure to viruses and bacteria, you can make changes to your daily life that will help support your immune system. 

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Your diet

Vitamin C

Eating plenty of food rich in vitamin C (for example broccoli, red peppers, citrus fruits oranges and blackcurrants) has been shown to support your immunity [3]. You should be able to get your daily requirement – 40mg ­– through diet alone.

Vitamin D

Vitamin D also helps to support your immune system [4]. It’s not present in sufficiently high quantities in foods (you can find it in the likes of oily fish and fortified foods such as cereals) so the NHS recommends supplementing with 10mcg or 400 IU per day, during the autumn and winter [5]. 

Zinc

Some studies have shown that the mineral zinc helps support the body’s immune system [6]. Women need about 7mg zinc a day and should be able to get enough through diet alone. Zinc-rich foods to tuck into include: shellfish (particularly oysters) and fish, meat, dairy foods, pumpkin seeds, walnuts and almonds.  

Probiotics and prebiotics

There is a strong link between what we eat, the microbes in our gut (microbiome) and our health. Around 70-80% of your immune cells are in your gut [7], and studies have found that probiotics and prebiotics can influence gut immunity [8]. Probiotics are live microorganisms that maintain or improve the good gut bacteria (microbiota), while prebiotics feed the gut microbiota.

Prebiotics can be found in raw vegetables and fruit, fermented pickles or dairy products, while probiotics occur naturally in cultured or fermented foods such as yogurt, kefir and sauerkraut.

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Hydration

Keeping hydrated is important for general health and studies have shown that exercise-induced dehydration can impact how well your immune cells do their job. While it can seem easier to drink plenty of water in the hot summer months, it’s important to drink enough in the winter too.

Things to limit

Sugary food and drinks, and food with a lot of white flour ingredients may reduce your immune functions [9] so try to restrict these.

Exercise

Just as exercise keeps you healthy, it can also improve your immunity – the key is to make sure you get the right amount. The NHS advises we do at least 150 minutes of moderate-intensity exercise a week or 75 minutes of vigorous exercise, spread over four to five days, plus strengthening exercises two days a week. Research has shown that moderate exercise lowers inflammation intensity and reducing susceptibility to respiratory infections [10].

However, it’s important not to over exercise, particularly when you are tired, as this has been shown to suppress the immune system. Listen to your body.

Don’t be put off by the cold weather though – it’s thought the cold can improve endurance, plus exercising outdoors can boost your mood.

Reduce stress

Most of us experience stressful moments but these are often unavoidable and have a minimal impact on your immunity. But when stress is more chronic, and lasts days or weeks, the increase in the stress hormone cortisol can reduce the production of white blood cells, which suppress the immune system. You’ll then be more susceptible to colds and viruses.  

Learn how to manage your stress by exploring activities such as mindfulness, meditation, yoga, exercise or spending time with friends and family.

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Sleep 

There is strong evidence that sleep provides essential support to your immune system. When you sleep there is an increased production of cytokines, proteins that act as messengers for the immune system, which are associated with inflammation. If you are ill or injured, this inflammation can help aid recovery but if you are well, it can work to strengthen adaptive immunity [12].

Conversely, sleep deprivation can make you sick – it has been shown to lead to a lower resistance to illness [13] and has been linked to chronic diseases such as diabetes.

Try to stick to a consistent routine, with the same bedtime and same awake time. You might find it helpful to use an app to help meditate, unwind or drift off to sleep, plus keep your room dark and cool, and stay off screens for an hour before you go to bed.

Sunshine 

Let’s face it, winter in the UK can be a little bleak but we do know that moderate exposure to sunlight can have a positive impact on your immune system – your body makes the important nutrient vitamin D when it’s exposed to sunlight. From October to March, it’s still worth getting outside (it’s especially good for your mental health), but take a vitamin D supplement to keep your levels topped up.

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References

1. NICE: common cold prevalence
2. Huang D, Taha MS, Nocera AL, Workman AD, Amiji MM, Bleier BS. (2023), ‘Cold exposure impairs extracellular vesicle swarm-mediated nasal antiviral immunity’, J Allergy Clin Immunol,151(2) pp.509-525. doi: 10.1016/j.jaci.2022.09.037
3. Gombart AF, Pierre A, Maggini S. (2020), ‘A Review of Micronutrients and the Immune System Working in Harmony to Reduce the Risk of Infection’, Nutrients, 12(1) pp.236. doi: 10.3390/nu12010236
4. Sassi F, Tamone C, D’Amelio P. (2018), ‘Vitamin D: Nutrient, Hormone, and Immunomodulator’, Nutrients, 10(11) pp.1656. doi: 10.3390/nu10111656
5. NHS vitamin D
6. Gombart AF, Pierre A, Maggini S. (2020), ‘A Review of Micronutrients and the Immune System Working in Harmony to Reduce the Risk of Infection,’ Nutrients. 12(1) pp.236. doi: 10.3390/nu12010236
7. Wiertsema SP, van Bergenhenegouwen J, Garssen J, Knippels LMJ. (2021), ‘The Interplay between the Gut Microbiome and the Immune System in the Context of Infectious Diseases throughout Life and the Role of Nutrition in Optimizing Treatment Strategies’, Nutrients. 9;13(3) pp. 886. doi: 10.3390/nu13030886
8. Vieira AT, Teixeira MM, Martins FS. (2013), ‘The role of probiotics and prebiotics in inducing gut immunity’, Front Immunol. 12;4:445. doi: 10.3389/fimmu.2013.00445.
9. Jafar N, Edriss H, Nugent K. (2016), ‘The Effect of Short-Term Hyperglycemia on the Innate Immune System’, Am J Med Sci. 351(2):201–211. doi: 10.1016/j.amjms.2015.11.011
10. Kurowski, M, Seys, S, Bonini, M, et al. (2022), ‘Physical exercise, immune response, and susceptibility to infections—current knowledge and growing research areas’, Allergy. 77: 2653–2664. doi: 10.1111/all.15328
11. Besedovsky L, Lange T, Born J. (2012), ‘Sleep and immune function’, Pflugers Arch, 463(1):121-37. doi: 10.1007/s00424-011-1044-0
12. Irwin MR. (2019), ‘Sleep and inflammation: partners in sickness and in health’, Nat Rev Immunol. (11):702-715. doi: 10.1038/s41577-019-0190-z
13. Cohen S, Doyle WJ, Alper CM, Janicki-Deverts D, Turner RB. (2009), ‘Sleep habits and susceptibility to the common cold’, Arch Intern Med. 169(1):62-7. doi: 10.1001/archinternmed.2008.505