Supporting immunity over winter
The cold and flu season has well and truly set in, but you might have wondered why we actually get sick more often in the colder months?
You can’t catch a cold from being out in the cold, throw that old wives tale in the bin, however there are a few factors to consider, as temperature does actually play a part.
The reason we get sick more often in winter is due to a number of factors relating to human behaviour, environmental factors and biology.
Firstly, as the weather gets colder and the days get shorter we spend more time inside and less time outside exposed to sunlight (gaining important vitamin D). Overseas travel also increases and we spend more time in close quarters with other people. This increases the transmission of viral particles from person to person (1).
Secondly, temperature and humidity affects how a virus replicates and spreads. Viral particles are more stable at lower temperatures; can stay airborne for longer with lower humidity levels; and the lower humidity causes the water molecule in the virus particle to evaporate faster, causing the particle to shrink (becoming lighter) and allowing it to travel further (1)(2).
Thirdly, our bodies' defence mechanisms are also affected by temperature and humidity. When the air is colder and dryer, the mucous secretions in our nose slow down and our innate immune response (bodies first line immune response) dampens, resulting in a delayed clearance of viral particles and more effective viral replication (1)(2).
In short, our immune defences are weaker and viruses are stronger in winter.
The immune system is a complex system designed to protect us from invading pathogens. It can be broken down into two main areas: innate immune response and adaptive immune response. The innate immune response is non-specific, fast acting and is activated by anything the body identifies as a pathogen and ‘non-self’. The adaptive immune system is slower acting and is activated by specific pathogens and uses the body's immunological memory to activate a defence (3).
The good news is that there are things we can do to bolster our immune system during this time.
Focus on a whole foods diet, rich in nutrients that support our immune system
Prioritise sleep
Support our nervous system
Exercise regularly
Limit alcohol and refined sugar
Ensure good hygiene practices
Immune nutrients
There are several nutrients that are essential in the proper functioning of both our innate and adaptive immune system, such as zinc, vitamin C, vitamin D and iron.
The body needs zinc for the development and function of the cells responsible for mediating our innate immune response, such as neutrophils and monocytes. It also helps to control our inflammatory response; and to regulate antibody and cell-mediated responses in relation to opportunistic pathogens. So, remember how our innate immune response dampens in cold weather; when our body is depleted of zinc it is also dampened and opportunistic pathogens (such as viruses) find it easier to replicate and take hold (4).
Vitamin C is not only a powerful antioxidant and anti-inflammatory, it stimulates the production of interferons (a protein) that protects cells against viral attack; enhances the activity of neutrophils and natural killer cells, which are part of our innate immune response; and also enhances the activity of B-cells and T-cells, which are part of our adaptive immune response. This enhancement also happens in the absence of illness, so vitamin C is a good one to keep on top of, especially in the winter months to support our innate immune response (4).
Vitamin D also plays a key role in our innate immune response. It enhances macrophage activity, which, along with neutrophils, aim to seek out and eliminate viruses before they can replicate (4).
Iron might not be something that comes to mind when we think about immunity, however it is required for the production and replication of cells in both the innate and adaptive immune system; and correcting iron deficiency has shown to both decrease the incidence of viral infections and increase the number of mature immune cells (4).
Ensuring to eat a wholefoods diet, rich in fresh, seasonal foods, will help us gain some of the essential nutrients that support our immune system. In the case of an acute immune event, supplementation at a dose higher than the RDI, can assist in faster recovery (4).
Sleep
Sleep plays an important regulatory role on our immune system as it supports the proper functioning of both our innate and adaptive immune systems; and reduces cellular inflammation and the production of pro-inflammatory cytokines. Subsequently, poor sleep causes immune dysfunction, where an increase in pro-inflammatory cytokines is seen, resulting in an increased risk of viral infection and/or a worsening of infection (5).
To support our immune system, adults need a minimum 7 hours sleep per night. Chronic sleep deprivation is classed as anything less than 6 hours per night, with daytime sleepiness nearly every day for a time period of at least 3 months (5).
Nervous system
Our nervous system is broken up into two parts- our sympathetic nervous system (fight or flight mode) and our parasympathetic nervous system (rest and digest mode). In times of chronic stress, our sympathetic nervous system becomes dominant causing our cortisol production to go into overdrive. This chronically elevated cortisol level results in a suppression of the body's inflammatory response, which increases pro-inflammatory cytokines and subsequently suppresses the immune system. This leads to an increased frequency of viral infection (6).
Focusing on activities that activate the parasympathetic nervous system, such as breathing exercises, gentle exercise, swimming, walking in nature, grounding, reading, journaling, or taking a bath, can reduce sympathetic nervous system dominance and improve our immune resilience.
Exercise
Regular exercise has various benefits on the immune system. It supports the parasympathetic nervous system activation, promotes an effective immune response, and exerts a systemic anti-inflammatory effect. It does this by redirecting immune cells to peripheral tissues acutely, which increases immune resilience during this time, decreasing macrophage response to inflammation, and by releasing anti-inflammatory cytokines which has a modulatory effect on the immune system (6, 7).
Acute strenuous exercise, can have the opposite effect, however, as it increases pro-inflammatory cytokines and our innate immune system response, resulting in an increased risk of acute viral infection but lower risk of chronic illness (6, 7).
Engaging in 150 minutes of regular, moderate intensity exercise per week has the greatest benefits on immune health, both acutely and chronically (6, 7).
Eating within 30-60 minutes of exercise also has beneficial effects, as it turns off the cortisol response to exercise. See more on my blog about this here.
Alcohol
Moderate alcohol consumption/binge drinking is associated with decreased immune system function as it inhibits the maturation of monocytes and reduces the production of pro-inflammatory cytokines necessary in the innate immune response. It also impairs the transcription and production of T-cells necessary for our adaptive immune response (8).
Moderate alcohol intake is classified as 1 standard drink per day for women and 2 per day for men. If you choose to drink, aim for 1-2 alcoholic beverages per week to prevent dampening your immune system (8).
Poor diet
A diet high in refined carbohydrates, added sugars and processed foods have a negative effect on the immune system. It does this as it shifts the microbiome away from beneficial bacteria that support the immune system towards non-beneficial bacteria; increases the production of inflammatory mediators and pro-inflammatory cytokines resulting in low grade chronic inflammation; and decreases the immune response to viral particles as cells from both the innate and adaptive immune system are drawn to protect the body against inflammation (9).
Hygiene
Ensuring proper hygiene practices is an important way to prevent viral particles entering the body.
Washing hands for 30 seconds, with warm water and soap, after touching public surfaces and prior to eating; avoid touching the face, mouth, eyes and nose; sneeze and cough into your elbow; use a humidifier at home, to moisten the air; and stay home if you are sick.
However, avoid using sanitisers (unless no soap and water is available) as this also kills the beneficial flora on our skin resulting in a microbial imbalance and a disruption to the skin barrier (10).
Remember, getting sick is not a bad thing- our immune system needs practice at defending our body from infection. The frequency of infection and how our body copes with getting sick is the important part.
If you suffer from more than 1-2 major viral infections per year or take longer than 7-10 days to get over it, your immune system could use some support.
Reach out to find out how I can help support your immune system to reduce the severity and frequency of illness.
Leisha x
References
Neumann, G., & Kawaoka, Y. (2022). Seasonality of influenza and other respiratory viruses. EMBO molecular medicine, 14(4), e15352.
Moriyama, M., Hugentobler, W. J., & Iwasaki, A. (2020). Seasonality of respiratory viral infections. Annual review of virology, 7(1), 83-101.
InformedHealth.org [Internet]. Cologne, Germany: Institute for Quality and Efficiency in Health Care (IQWiG); 2006-. In brief: The innate and adaptive immune systems. [Updated 2023 Aug 14]. Available from: https://www.ncbi.nlm.nih.gov/books/NBK279396/
Braun, L., Cohen, M. (2015). Herbs and Natural Supplements, Volume 2: An Evidence-Based Guide. United Kingdom: Elsevier Health Sciences.
Garbarino, S., Lanteri, P., Bragazzi, N. L., Magnavita, N., & Scoditti, E. (2021). Role of sleep deprivation in immune-related disease risk and outcomes. Communications biology, 4(1), 1304. https://doi.org/10.1038/s42003-021-02825-4
Zefferino, R., Di Gioia, S., & Conese, M. (2021). Molecular links between endocrine, nervous and immune system during chronic stress. Brain and behavior, 11(2), e01960.
da Luz Scheffer, D., & Latini, A. (2020). Exercise-induced immune system response: Anti-inflammatory status on peripheral and central organs. Biochimica et Biophysica Acta (BBA)-Molecular Basis of Disease, 1866(10), 165823.
Barr, T., Helms, C., Grant, K., & Messaoudi, I. (2016). Opposing effects of alcohol on the immune system. Progress in neuro-psychopharmacology & biological psychiatry, 65, 242–251. https://doi.org/10.1016/j.pnpbp.2015.09.001
Ma, X., Nan, F., Liang, H., Shu, P., Fan, X., Song, X., Hou, Y., & Zhang, D. (2022). Excessive intake of sugar: An accomplice of inflammation. Frontiers in immunology, 13, 988481. https://doi.org/10.3389/fimmu.2022.988481
Himabindu, C. S. H. C. S., Tanish, B. T. B., Kumari, N. P. K. N. P., & Nayab, S. N. S. (2020). Hand sanitizers: is over usage harmful?. World journal of current medical and pharmaceutical research, 296-300.