Days are getting shorter and colder, signaling that it's that time of year again – for the seasonal crud! Contrary to what the media might have you believe; a shot is not the only way to protect yourself from bad bugs this fall and winter! Read on to learn how you can reduce your chances of catching a bug by fortifying your immune system with nutrition and healthy lifestyle habits.
A Brief Overview of the Immune System
Your immune system is a complex network of cells, tissues, and organs that protects your body from harmful microorganisms while preventing an inappropriate attack on your own body. It includes the thymus, a small gland in the top part of your chest, the spleen, lymph nodes, as well as barriers such as your skin and mucous membranes of your nose and gastrointestinal tract.
Broadly speaking, the immune system has two major branches: Innate immunity and adaptive immunity. The innate immune response involves an immediate, nonspecific response to foreign invaders such as bacteria and viruses. It is comprised of physical and chemical barriers, including your skin, stomach acid, intestinal mucosa, gut bacteria, and small molecules such as antiviral interferons.
Adaptive immunity is more complicated because it involves the creation of immunologic memory, a process whereby the immune system learns to quickly and correctly recognize foreign invaders and launch a corresponding immune response. Immunologic memory is mediated by specialized immune cells called B and T cells.
Why are We More at Risk in the Winter?
If our immune systems are so adept at managing bacteria, viruses, and other harmful invaders, then why do people so often feel under the weather in the fall and winter? Research shows that colder temperatures, a lack of sun exposure leading to low vitamin D levels, and our tendency to stay cooped up indoors when it is cold outside hinder our immune defenses, allowing bacteria and viruses to better replicate in our bodies and increase our chances of becoming their victim.1,2,3
6 Strategies for Supporting Your Immune System this Winter
By keeping your immune system in tip-top shape, you can increase your chances of staying healthy and active all season long. Optimal nutrition, potent botanicals and nutraceuticals, and healthy lifestyle habits can help you keep your immune system chugging along.
Support Your Immune System with Nutrition
Ensuring optimal nutritional status is a crucial first step towards supporting immunity. A variety of vitamins and minerals contribute to the function of immune cells and the integrity of your first-line immune system defenses, including the tissues in your nasal passages and gastrointestinal tract. Deficiencies of these micronutrients can cause immune suppression, increasing your odds of getting a bug. Vitamins A, D, E, C, zinc, and omega-3 fatty acids are a few of the nutrients that are most important for supporting your immune system.
Vitamin D is a fat-soluble vitamin that is made when UVB light from the sun hits our skin, transforming a cholesterol-based precursor compound into the first molecule in the human vitamin D synthesis pathway. A growing body of research indicates that vitamin D is a critical node in the immune system, regulating the response to infections, among many other functions. Our increased propensity for getting sick in the winter may be due to a lack of sun exposure, which leads to low vitamin D levels and compromised immune defenses.
Vitamin D has several effects that may help ward off bugs in the winter. It has direct antiviral activity, upregulating the production of antimicrobial immune molecules, including LL-37 and human beta-defensin 2.4 It regulates cells involved in both the innate and adaptive immune responses, including monocytes, macrophages, and activated T cells. People who have a vitamin D deficiency or a reduced responsivity of their vitamin D receptors (VDR) to vitamin D have an increased risk of upper respiratory problems compared to those sufficient in vitamin D.5 Thus, people with low vitamin D levels or VDR variants may benefit from vitamin D3 supplementation in the fall and winter.2
Alongside supplementation, you can support a robust vitamin D level by eating fatty cold-water fish, such as wild salmon, and egg yolks. Sunlight typically isn't a viable source of vitamin D in winter for people who live at high latitudes in North America, but you can "stock up" on vitamin D in the spring and summer months by spending plenty of time outdoors.
Vitamin C has long been promoted as a protective intervention for reducing the risk of illness in the winter. Vitamin C has multiple beneficial effects on the immune system, including stimulating the production and function of white blood cells and protecting immune cells from oxidative damage.6
An extensive scientific review found that supplementation with 1-2 grams of vitamin C per day during illness significantly reduces the duration of the common cold. This effect may be due to the ability of vitamin C to increase antiviral defenses, including the production of interferon and neutrophils.7,8
High plasma levels of vitamin C are required for the prevention and treatment of infections. Studies arguing that supplemental vitamin C has no effect on combatting seasonal wellness issues are confounded by the poor bioavailability of standard oral vitamin C supplements, a factor that limits plasma levels of the vitamin. Liposomal formulations significantly increase the bioavailability of vitamin C, allowing you to achieve the high plasma levels of this nutrient necessary to boost your immune defenses.9
Vitamin A is a critical but often overlooked nutrient for immune health. Preformed vitamin A (retinol, retinoic acid) is essential for supporting both innate and adaptive immunity. Vitamin A maintains immunity at epithelial barriers, including those in the gut and respiratory tract.10 It is also required for the activation of T and B cells in adaptive immunity and enhances the immune response to illness.11
While vitamin A can be made from beta-carotene, a carotenoid found in yellow and orange vegetables, this conversion is inefficient in many people, necessitating dietary intake of preformed vitamin A either from a supplement or from foods such as beef liver, cod liver oil, and full-fat dairy products.12
Vitamin E is not the first vitamin that comes to mind when most people think of the immune system. However, research indicates that vitamin E plays a critical role in immunity by protecting immune cell membranes from oxidative damage, thus preserving the integrity of the immune system.13 Research suggests that vitamin E supplementation reduces the risk of upper respiratory issues.14 It may work best to support immunity when taken together with its sister fat-soluble vitamins, vitamins A and D.
A deficiency of zinc, an essential mineral for the human body, impairs immunity on multiple levels; it decreases natural killer cell activity, alters the function of T and B cells, and alters gene expression in immune system pathways. Supplemental zinc may shorten the duration of common illnesses when consumed in a lozenge form.15,16
Omega-3 fatty acids
Omega-3 fatty acids are essential fatty acids that our bodies cannot make on their own, so we must consume them in our diets. The omega-3’s, including ALA, EPA, and DHA, are well-known for their anti-inflammatory effects; however, they also appear to play crucial roles in the regulation of immunity. Omega-3 fatty acids help form the membranes of immune cells, where they affect immune cell signaling. They also enhance phagocytosis, or the ingestion of pathogenic bacteria by specialized immune cells.17
However, when it comes to omega-3 fatty acids and immunity, it’s all about balance! Excessive consumption of omega-3 fatty acids (such as occurs when people mega-dose fish oil) at the expense of omega-6 fatty acids may impair the immune response to harmful bacteria. If you eat a balanced diet that includes 2-3 servings of seafood per week and unprocessed sources of omega-6 fatty acids, such as meat, poultry, and nuts, you should be able to maintain a good omega-3/omega-6 balance and healthy immune function.
Optimize Immune Function with Botanicals and Nutraceuticals
Botanicals and nutraceuticals can be used alongside nutrition to further support your immune system in the fall and winter. Cat's Claw, monolaurin, and glutathione are especially beneficial for enhancing immune function and promoting a healthy internal microbial balance.
Cat’s Claw (Uncaria tomentosa) is a botanical from the Amazon region of South America. It has potent antiviral and immunomodulatory properties that make it a powerful ally for supporting healthy immune function in the fall and winter.18
Monolaurin is a fatty acid that is naturally found in coconut products and human breast milk; in fact, it contributes to the broad antimicrobial properties of breast milk that assist in building up an infant’s immune system.19 It has extensive antimicrobial and antiviral activities and upregulates the growth of beneficial gut bacteria, which have natural immune-supportive properties.20
Glutathione is a crucial cellular antioxidant and powerful detoxifier for the body. However, it also plays a critical role in healthy immune function! It’s shown to optimize immune function in the respiratory tract and fine-tune the immune response towards illnesses.21,22
Probiotics are defined as "live microorganisms which, when administered in adequate amounts confer a health benefit on the host."23 While probiotics have been the most thoroughly investigated for their effects on digestive system health, emerging research suggests that they may also help protect us against seasonal suffering!
In adults susceptible to frequent health interruptions, supplementation with Lactobacillus paracasei, Lactobacillus casei, and Lactobacillus fermentium for 12 weeks was found to significantly reduce the incidence of upper respiratory problems, possibly by increasing levels of an antiviral molecule called interferon.24 Probiotic species in kimchi, a traditional fermented vegetable dish from Korea, and miso, a fermented soybean dish, have antiviral effects and upregulate immunity.25,26 Various probiotic species also help maintain the intestinal barrier, which is a critical component of the immune system.27 Regularly consuming fermented foods and taking a broad-spectrum probiotic may help strengthen your immune system, keeping you well throughout the fall and winter.
Get Some Fresh Air and Sunshine!
As recently as 150 years ago, hospitals were designed with large windows between patient beds, to ensure cross-ventilation and abundant sunlight. The designers of these hospitals intuitively understood that fresh air and sunshine helped people heal. Today, we have scientific evidence demonstrating that sunlight boosts immunity by increasing vitamin D levels and helps control the spread of pathogens by inducing the production of damaging reactive oxygen species in pathogens.28 Recirculated air, in contrast to fresh air, allows airborne pathogens to linger inside buildings, where they can take advantage of those with compromised immune systems and cause illness.
You can mitigate the pathogen load of recirculated air by periodically opening up windows to let in fresh air, and by investing in a high-quality air filter. Don’t forget to spend some time outdoors each day in the sun (if it’s available!) throughout the fall and winter to get some immune-boosting sunshine!
Get Plenty of Sleep
Without sufficient high-quality sleep, nearly every aspect of our health suffers, including immunity. A short sleep duration and low-quality sleep increases the risk.29 Sleep deprivation weakens immunity by reducing natural killer cell activity and increasing inflammation, which diverts precious energy away from your immune defenses.30
Support your immune system by allocating time for 7-8 hours of sleep each night (for some people, this may mean allocating time for 7.5-8.5 hours of time in bed, depending on how long it takes for you to fall asleep). You can optimize your sleep quality by wearing blue-light-blocking glasses before bed to optimize melatonin production, creating a relaxing bedtime routine, and sleeping in a completely dark, cool bedroom.
Last but certainly not least, don’t forget about the importance of exercise for keeping your immune system in optimal shape! Regular, moderate-intensity exercise may reduce the risk of catching something by enhancing the ability of the immune system to respond to infectious threats.31,32 Frequent exercise might delay aging of the immune system, supporting robust immunity throughout the lifespan.
Find a form of physical activity that feels good to you and aim to do it at least 4-5 days of the week. Allow for plenty of rest time between hard workout sessions to make sure you don’t overtax your body and your immune system.
Feeling unwell is not an inevitable part of fall and winter. By providing your body with nutrients and botanicals that promote healthy immune function, as well as probiotics, fresh air, sunshine, sleep, and consistent physical activity, you can keep your immune system in tip-top shape all season long!
- Foxman EF, et al. Temperature-dependent innate defense against the common cold virus limits viral replication at warm temperature in mouse airway cells. Proc Natl Acad Sci USA. 2015; 112(3): 827-832.
- Martineau AR, et al. Vitamin D supplementation to prevent acute respiratory tract infections: systematic review and meta-analysis of individual participant data. BMJ. 2017; 356: i6583.
- Sundell N, et al. A four year seasonal survey of the relationship between outdoor climate and epidemiology of viral respiratory tract infections in a temperate climate. J Clin Virol. 2016; 84: 59-63.
- Beard JA, et al. Vitamin D and the anti-viral state. J Clin Virol. 2011; 50(3): 194-200.
- Jolliffe DA, et al. Vitamin D receptor genotype influences risk of upper respiratory infection. Br J Nutr. 2018; 120(8): 891-900.
- Mousavi S, et al. Immunomodulatory and antimicrobial effects of vitamin C. Eur J Microbiol Immunol (Bp). 2019; 9(3): 73-79.
- Hemila H, Chalker E. Vitamin C for preventing and treating the common cold. Cochrane Database Syst Rev. 2013; 1: CD000980.
- Kim Y, et al. Vitamin C Is an Essential factor on the anti-viral immune responses through the production of interferon-α/β at the initial stage of influenza A virus (H3N2) infection. Immune Netw. 2013; 13(2): 70-74.
- Carr AC, Maggini S. Vitamin C and immune function. Nutrients. 2017; 9(11): 1211.
- Sirisinha S. The pleiotropic role of vitamin A in regulating mucosal immunity. Asian Pac J Allergy Immunol. 2015; 33(2): 71-89.
- Cui D, et al. High-level dietary vitamin A enhances T-helper type 2 cytokine production and secretory immunoglobulin A response to influenza A virus infection in BALB/c mice. J Nutr. 2000; 130(5): 1132-1139.
- Tang G. Bioconversion of dietary provitamin A carotenoids to vitamin A in humans. Am J Clin Nutr. 2010; 91(5): 1468S-1473S.
- Lee GY, Han SN. The role of vitamin E in immunity. Nutrients. 2018; 10(11): 1614.
- Meydani SN, et al. Vitamin E and respiratory tract infections in elderly nursing home residents: A randomized controlled trial. JAMA. 2004; 292(7): 828-836.
- Maywald M, et al. Zinc signals and immunity. Int J Mol Sci. 2017; 18(10): 2222.
- Hemila H. Zinc lozenges and the common cold: a meta-analysis comparing zinc acetate and zinc gluconate, and the role of zinc dosage. JRSM Open. 2017; 8(5): 2054270417694291.
- Gutierrez S, et al. Effects of omega-3 fatty acids on immune cells. Int J Mol Sci. 2019; 20(20): 5028.
- Williams JE. Review of antiviral and immunomodulating properties of plants of the Peruvian rainforest with a particular emphasis on Una de Gato and Sangre de Grado. Altern Med Rev. 2001; 6(6): 567-579.
- Schlievert PM, et al. Glycerol monolaurate contributes to the antimicrobial and anti-inflammatory activity of human milk. Sci Rep. 2019; 9: 14550.
- Mo Q, et al. High-dose glycerol monolaurate up-regulated beneficial indigenous microbiota without inducing metabolic dysfunction and systemic inflammation: New insights into its antimicrobial potential. Nutrients. 2019; 11(9): pii: E1981.
- Ghezzi P. Role of glutathione in immunity and inflammation in the lung. Int J Gen Med. 2011; 4: 105-113.
- Diotallevi M, et al. Glutathione fine-tunes the innate immune response toward antiviral pathways in a macrophage cell line independently of its antioxidant properties. Front Immunol. 2017; 8: 1239.
- Reid G, et al. Probiotics: Reiterating what they are and what they are not. Front Microbiol. 2019. 10: 424.
- Zhang H, et al. Prospective study of probiotic supplementation results in immune stimulation and improvement of upper respiratory infection rate. Synth Syst Biotechnol. 2018; 3(2): 113-120.
- Park S, et al. Effects of heat-killed Lactobacillus plantarum against influenza viruses in mice. J Microbiol. 2018; 56(2): 145-149.
- Kumazawa T, et al. Isolation of immune-regulatory Tetragenococcus halophilus from miso. PLoS One. 2018; 13(12): e0208821.
- La Fata G, et al. Probiotics and the gut immune system: Indirect regulation. Probiotics Antimicrob Proteins. 2018; 10(1): 11-21.
- Hobday RA, Dancer SJ. Roles of sunlight and natural ventilation for controlling infection: historical and current perspectives. J Hosp Infect. 2013; 84(4): 271-282.
- Cohen S, et al. Sleep habits and susceptibility to the common cold. Arch Intern Med. 2009; 169(1): 62-67.
- Asif N, et al. Human immune system during sleep. Am J Clin Exp Immunol. 2017; 6(6): 92-96.
- Lee HK, et al. The effect of exercise on prevention of the common cold: A meta-analysis of randomized controlled trial studies. Korean J Fam Med. 2014; 35(3): 119-126.
- Campbell JP, Turner JE. Debunking the myth of exercise-induced immune suppression: Redefining the impact of exercise on immunological health across the lifespan. Front Immunol. 2018; 9: 648.