Fighting the winter flu; supporting your immune system?”

Chiropractic Consultation

It’s winter, the days are shorter and the temperatures are dropping. Most of us know someone who’s caught this most recent flu. So why does the flu arise every winter and what can we do about it? 

The flu spreads most effectively when we have a combination of factors such as temperature (<5⁰)  and humidity (<35%). Whilst in the UK we see many wet or humid days, the combination of the dryness of the indoor environment and the contrasting cold outdoor temperatures still allow the flu to spread ¹. However, many other factors influence flu seasonality so there is no single conclusive explanation for this phenomenon.

The shortening of the day also affects our immune system as we are unable to absorb as much vitamin D from sunlight exposure. Vitamin D increases the activity of macrophages and monocytes, which surround and consume the pathogens in our body. It also ensures we have an appropriate immune response to the pathogens preventing an excessive increase in inflammation (↑anti-inflammatory signaling, ↑regulatory T-cells, & ↓pro-inflammatory cytokines) ².

But what if supplementing vitamin D isn’t accessible? This is where exercise is fantastic, it is able to increase the circulation of the cells allowing our body to identify pathogens more quickly. An important note here is that the exercise is of moderate intensity as overtraining and competing is linked to a higher risk of illness ³. So what is moderate intensity? A practical approach would be to pay attention to your breathing; if you are taking deeper breaths whilst remaining able to speak this indicates that you are at an appropriate level of exercise intensity for moderate intensity. If you use heart rate (HR) zones for your training then this would be the equivalent of zone 3 (70-80% Max HR). 

So by maintaining vitamin D levels and regularly exercising we can improve immune resilience without complex routines or drastic lifestyle changes. 

References:

1. Lowen, A.C. and Steel, J. (2014) Roles of humidity and temperature in shaping influenza seasonality, Journal of virology. Available at: https://pmc.ncbi.nlm.nih.gov/articles/PMC4097773/ (Accessed: 25 January 2026).

2. Gleeson, M. (2007b) Immune Function in sport and exercise, Journal of applied physiology (Bethesda, Md. : 1985). Available at: https://pubmed.ncbi.nlm.nih.gov/17303714/ (Accessed: 25 January 2026).

3. Walsh , N.P. et al. (2011) ‘Position statement. Part one: Immune function and exercise’, Exercise and Immunology Review, 17, pp. 6–63.