As the colder months arrive, many people look for ways to avoid seasonal colds and flu. From vitamin C supplements to traditional advice about keeping warm, there is no shortage of recommendations about how to stay healthy. But how much of this advice is supported by science?
Our immune system is a complex network of cells, tissues and organs that work together to protect the body against infection. While no single food or lifestyle change can prevent illness, research suggests that several everyday habits can help support normal immune function.
Here are five areas worth considering.
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Stress and immune function
Stress triggers a series of physiological responses involving hormones such as cortisol, which help the body respond to perceived threats. While this is a normal protective mechanism, prolonged exposure to stress hormones can influence immune cell activity and inflammatory responses. Research suggests that chronic stress may affect the body’s ability to regulate its immune response effectively.
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Sleep and immune response
Sleep plays an important role in maintaining normal immune function. During sleep, the body regulates immune signalling processes, including the release of cytokines, proteins involved in coordinating the immune response. Research has also linked insufficient sleep with changes in immune cell activity and a reduced response to certain infections and vaccinations.
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Diet, gut bacteria and immunity
The gut microbiome plays an important role in immune regulation, with dietary fibre helping to support the diverse communities of bacteria living in the digestive system. As gut microbes break down fibre, they produce short-chain fatty acids, which contribute to maintaining the gut barrier and regulating inflammatory and immune responses.
A varied diet containing vegetables, fruit, beans, wholegrains, nuts and seeds provides important sources of fibre. Fermented foods, including yoghurt, kefir, kimchi and sauerkraut, can also contribute to dietary diversity.
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Physical activity and immune function
Regular physical activity is associated with positive effects on immune regulation. Exercise stimulates the movement of immune cells through the bloodstream, helping the body monitor for potential infections. It is also associated with improvements in inflammatory regulation and broader metabolic health.
Research suggests that moderate, regular activity supports immune function, while prolonged, intensive exercise without adequate recovery can have different effects. The relationship between exercise and immunity is therefore influenced by both intensity and duration.
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Vitamins, minerals and immune health
Several vitamins and minerals are essential for normal immune function. Vitamin C contributes to the function of immune cells and helps protect them from oxidative damage, while vitamin D plays a role in regulating immune responses. Zinc is also important for the development and functioning of immune cells.
However, this does not mean that taking additional supplements will necessarily prevent infection. For people who already obtain sufficient nutrients through their diet, there is limited evidence that extra supplementation provides meaningful protection against colds and flu. Supplements are most useful where a deficiency exists or where additional intake has been recommended by a healthcare professional.
What about common cold and flu myths?
Getting cold or wet does not directly cause a cold – respiratory infections are caused by viruses. Similarly, while vitamin C is essential for immune health, taking supplements is not a guaranteed way to avoid seasonal infections.
Understanding the difference between supporting normal immune function and actively preventing infection is important when assessing the many health claims that circulate during winter.
The takeaway
There is no quick fix for avoiding winter illnesses, and no single food can guarantee protection against infection. However, the evidence points towards a combination of good-quality sleep, stress management, regular physical activity and a varied, fibre-rich diet as important foundations for supporting immune health.
Alongside these everyday habits, staying up to date with recommended vaccinations and practising good hygiene remain important measures for reducing the risk of seasonal infections.
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