Here you go. This article outlines some immune system boosting foods to include into your diet! This article is research based involving some aspects of immunonutrition so that you can be confident that your immune system is at its absolute optimum [1, 2]. If you aren’t bothered by the science, here is the summary! :)
Summary:
Maintain a healthy body size
Consume vitamin A from fortified low-fat spreads, broccoli, spinach, carrots, sweet potatoes, red peppers, mango, papaya and apricots.
Consume vitamin C from grapefruit, oranges, kiwi, papaya (papaya and kiwi are also full of other beneficial nutrients), tangerines, lemons, limes, clementines, red bell peppers, broccoli and spinach. Also consider taking a supplement.
Try to get outside or spend time in the garden for safe sunlight exposure when you can, and consider taking a 10 microgram vitamin D supplement to reduce the risk of deficiency during lockdown.
Have almonds, sunflower seeds, avocados, broccoli and dark leafy greens for vitamin E.
Get omega-3 from flaxseed, walnuts, chia and hemp and consider taking an algae based omega-3 supplement.
Consume selenium from brazil and walnuts.
Spinach and broccoli are also a great source of multiple antioxidants, especially when lightly cooked.
Include more garlic, ginger and turmeric in the diet.
Eat foods that promote a healthy gut microbiome such as garlic, onions, leeks, asparagus, artichokes, tomatoes, bananas, plums and apples, grains, cereals, nuts, kombucha, kimchi, sauerkraut and miso or a supplement.
An immune system that functions well is the best defence against pathogenic organisms to the body. The immune system identifies these pathogens as either dangerous or not and sends an appropriate amount of cells to go and fight off the pathogen [3, 4]. Rather like a police officer identifying a criminal and calling in for reinforcements. Luckily for us, numerous nutrients have been identified that directly influence the immune system. Tailoring your diet towards these nutrients may well help to boost immune system function and help you to right off disease [5]. Whilst this does not guarantee that you won’t pick up an infection, you can rest your mind knowing that your body is the most prepared it can be to protect you if you were to get sick.
An important aspect of health in general, but particularly immune system function is having a healthy body size. Both malnutrition and obesity alike have strong evidence of causing poor immune system function resulting in an individual being less able to prevent and deal with infections as they arise [6, 7, 8]. In particular, obesity has been shown to impair the immune system response to influenza (flu) putting individuals at an increased risk of hospitalisation and poor health outcomes [9, 10, 11].
A note on COVID-19:
A systematic review aimed to research potential treatment options for COVID-19 has given recommendations for nutrition to boost the immune system [12]. The specific nutrients highlighted include B vitamins, vitamins A, C, D and E, omega-3, selenium, zinc and iron. Below I have elaborated on some of these nutrients and the foods they can be found in. It must be noted that these, including the other potential treatment options outlined in the article are only theoretical and not yet proven effective treatments. If you wish to read the original research article, you can find a link to it in the references below [12].
Vitamin A
Vitamin A is a fat soluble vitamin which means in can be stored in the body. Vitamin A or its precursor beta carotene can be found in fortified low-fat spreads, broccoli, spinach, carrots, sweet potatoes, red peppers, mango, papaya and apricots. Vitamin A can help the immune system by reducing inflammation, immune system development and regulating cellular immune response [13]. Vitamin A has been shown to offer protection agains some infections including malaria, lung infections, and HIV [12]. Supplementation of vitamin A is not recommended.
Vitamin C
Vitamin C is water-soluble which means it is not easily stored in the body. It can be found in grapefruit, oranges, kiwi, papaya (papaya and kiwi are also full of other beneficial nutrients), tangerines, lemons, limes, clementines, red bell peppers, broccoli and spinach. Vitamin C is thought to increase the production of white blood cells, support a barrier against pathogens, the destruction of pathogens, apoptosis of infected cells and protects the body against oxidative stress. Vitamin C supplementation appears to be able to prevent and treat respiratory tract and systemic infections [14, 15]. For example, vitamin C has been shown in multiple studies to reduce the duration and severity of the common cold and flu-like symptoms [12, 16]. Supplementation is generally and can be taken if an individual feels the need.
Vitamin D
Vitamin D is a fat soluble vitamin that can be synthesised by the skin providing an individual receives enough safe sunlight. Vitamin D modulates the response of the immune system by directly binding to immune system cells such as antigen-presenting-cells, T-cells, B-cells and monocytes [17, 18]. Vitamin D is potentially effective to prevent and reduce the severity of the common cold [16]. Regardless of the effects of vitamin D on the immune system, the current recommendations are for the general population to take 10 micrograms of vitamin D supplementation. This is to counter the effects of poor sunlight exposure and the subsequent risk of vitamin D deficiency whilst we are all inside our houses for longer periods of time [12].
Vitamin E
Vitamin E is found in almonds, sunflower seeds, avocados, broccoli and dark leafy greens. Vitamin E is a fat soluble vitamin which works as a powerful antioxidant to help reduce oxidative stress and inflammation [12]. Vitamin E can have an effect on the development, function and regulation of immune system related cells, particularly T-cells to reduce the risk of infection, including susceptibility to respiratory infections [19, 20]. Vitamin C and E work together as antioxidants as vitamin C has the ability to repair vitamin E following electron donation. Together, alongside other antioxidants, they can rescue or prevent tissue damage following physiological response to foreign bodies (such as an infection). Therefore they are valuable in promoting health during and following an infection [21]. A supplement for vitamin E is probably unnecessary as a person is likely to get enough from their diet.
Omega-3
Alpha-lipoic acid (ALA) is also a great antioxidant which is derived from omega-3 and can be found in seeds and oils such as flaxseed, walnuts, chia and hemp [15]. Omega-3 can promote anti-inflammatory effects [12]. Supplements of plant-based omega-3 could be recommended to those who lack this nutrient, especially those who follow a plant-based diet [22].
Selenium
Selenium is an essential trace element. It can be found in brazil and walnuts. Selenium also works as an antioxidant and dietary deficiency can become problematic to the immune system [12]. Eating selenium containing foods is recommended.
Garlic
Garlic has been recognised across the world for centuries for its ability to help fight infections. Garlic has been found in recent studies to modulate immune cell distribution amongst other benefits, contributing to reduced inflammation and destruction of pathogens [23, 24]. In particular it has been of benefit in the reduction of severity of cold and flu symptoms [23].
Ginger
Ginger is known to decrease inflammation and nausea [25]. This is likely due to the gingerol it contains. Fresh ginger is generally considered better than its dried alternative [26]. However, the essential oil derived from ginger has also showed promising immune function enhancing properties in multiple studies [27].
Turmeric (Curcumin)
Turmeric (curcumin) has been long known for its anti-inflammatory and anti-oxidative effects and can also cause epigenetic changes in immune cells (changes in gene expression from the environment) in many areas of the body [28, 29, 30]. Curcumin works particularly on the expression and production of T-cells and cytokines involved in the anti-inflammatory immune response, and enhancing their action on tissues [31, 32].
Gut Microbiome
The last important aspect of a healthy immune system is the gut microbiome. More and more research is being carried out to reveal the immense importance of the influence of the gut microbiota on a multitude of bodily processes and the associated chronic health conditions. There is increasing evidence regarding the influence of the gut microbiota on the immune system [1, 4]. Foods to promote a healthy gut microbiome and thus the immune system include pre and probiotics [3]. Prebiotics can be found in vegetables and fruit such as garlic, onions, leeks, asparagus, artichokes, tomatoes, bananas, plums and apples, grains, cereals and nuts. Probiotics contain healthy bacteria and are usually found in fermented foods such as kombucha, kimchi, sauerkraut and miso or a supplement.
Safe wishes to everybody and please don't hesitate to contact me if you have concerns or anxieties.
Lottie x
References:
[1] Zapatera, B., Prados, A., Gómez-Martínez, S. and Marcos, A. (2015) ‘Immunonutrition: methodology and applications’, 31 (3), pp. 145-154.
[2] Papadopoulos, N., Megremis, S., Kitsioulis, N., Vangelatou, O., West, P. and Xepapadaki, P. (2017) 'Promising approaches for the treatment and prevention of viral respiratory illnesses’, J Allergy Clin Immunol, 140 (4), pp. 921-932.
[3] Calder, P. (2013) ‘Feeding the immune system’, Proc Nutr Soc, 72 (3). pp. 299-309.
[4] Childs, C., Calder, P. and Miles, E. (2019) ‘Diet and Immune Function’, Nutrients, 11 (8), pp. E1933.
[5] Maggini, S., Pierre, A. and Calder, P. (2018) ‘Immune Function and Micronutrient Requirements Change over the Life Course’, Nutrients, 10 (10), pp. E1531.
[6] Cohen, S., Danzaki, K. and MacIver, N. (2017) ‘Nutritional effects on T-cell immunometabolism’, Eur J Immunol, 47 (2), pp. 225-235.
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[10] Neidich, S., Green, W., Rebeles, J., Karlsson, E., Schultz-Cherry, S., Noah, T., Chakladar, S., Hudgens, M., Weir, S. and Beck, M. (2017) ‘Increased risk of influenza among vaccinated adults who are obese’, International Journal of Obesity, 41 (9), pp. 1324-1330.
[11] Honce, R. and Schultz-Cherry, S. (2019) ‘Impact of Obesity on Influenza; A Virus Pathogenesis, Immune Response, and Evolution’, Front Immunol, 10, pp. 1071.
[13] Huang, Z., Liu, Y., Qi, G., Brand, D. and Zheng, S. (2018) ‘Role of Vitamin A in the Immune System’, Journal of Clinical Medicine, 7 (9), pp. E258.
[14] Carr, A and Maggini, S. (2017) ‘Vitamin C and Immune Function’, Nutrients, 9 (11), pp. E1211.
[15] El-Senousey, H., Chen, B., Wang, J., Atta, A., Mohamed, F., and Nie, Q. (2018) ‘Effects of dietary vitamin C, vitamin E, and alpha-lipoic acid supplementation on the antioxidant defense system and immune-related gene expression in broilers exposed to oxidative stress by dexamethasone’, Poult Sci, 97 (1), pp. 30-38.
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[17] Prietl, B., Treiber, G., Pieber, T. and Amrein, K. (2013) ‘Vitamin D and immune function’, Nutrients, 5 (7), pp. 2502-2521.
[18] Carlberg, C. (2019) ‘Nutrigenomics of Vitamin D’, Nutrients, 11 (3). pp. E676.
[19] Lee, G, and Han, S. (2018) ‘The Role of Vitamin E in Immunity’, 10 (11), pp. E1614.
[20] Lewis, E., Meydani, S. and Wu, D. (2019) ‘Regulatory role of vitamin E in the immune system and inflammation’, IUBMB Life, 71 (4), 487-494.
[21] Arulselvan, P., Fard, M., Tan, W., Gothai, S., Fakurazi, S., Norhaizan, M. and Kumar, S. (2016) ‘Role of Antioxidants and Natural Products in Inflammation’, Oxidative Medicine and Cellular Longevity, Epub 5276130.
[22] Soldati, L., Di Renzo, L., Jirillo, E., Ascierto, P., Marincola, F. and De Lorenzo, A. (2018) ‘The influence of diet on anti-cancer immune responsiveness’, J Transl Med, 16 (1), pp. 75.
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[25] Aryaeian, N., Shahram, F., Mahmoudi, M., Tavakoli, H., Yousefi, B., Arablou, T. and Jafari Karegar, S. (2019) ‘The effect of ginger supplementation on some immunity and inflammation intermediate genes expression in patients with active Rheumatoid Arthritis’, Gene, 698, pp. 179-185.
[26] Lee, J., Kim, B., Kim, J., Jeong, M., Lim, S. and Byun, S. (2019) ‘Effect of Differential Thermal Drying Conditions on the Immunomodulatory Function of Ginger’, J Microbiol Biotechnol, 29 (7), pp. 1053-1060.
[27] Peterfalvi, A., Miko, E., Nagy, T., Reger, B., Simon, D., Miseta, A., Czéh, B. and Szereday, L. (2019) ‘Much More Than a Pleasant Scent: A Review on Essential Oils Supporting the Immune System’, Molecules, 24 (24), pp. E4530.
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[30] Wojcik, M., Krawczyk, M., Wojcik, P., Cypryk, K. and Wozniak, L. (2018) ‘Molecular Mechanisms Underlying Curcumin-Mediated Therapeutic Effects in Type 2 Diabetes and Cancer’, Oxid Med Cell Longev, Epub 9698258.
[31] Momtazi-Borojeni, A., Haftcheshmeh, S., Esmaeili, S., Johnston, T., Abdollahi, E. and Sahebkar, A. (2018) ‘Curcumin: A natural modulator of immune cells in systemic lupus erythematosus’, Autoimmun Rev, 17 (2), pp. 125-135.
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