Let Food Be Thy Immune Booster

You may have heard the quote by Hippocrates, the father of medicine, “Let food be thy medicine”. Well he was right, food can be our medicine, but it can also be the cause of disease and poor health.

There are numerous reasons someone may be more susceptible to colds and flues: stress, exposure to environmental toxins, heavy metals, industrial chemicals, chemotherapy and radiation, ageing, poor sleep/ insomnia, chronic disease, and malnutrition [1].

1. Malnutrition
   
   Malnutrition is seen as an issue affective those in third world countries. With our access to highly processed, fast foods, malnutrition has become all too common in western countries as well. High refined carbohydrate diets and diets low in fresh fruits and vegetables can lead to deficiencies in many nutrients needed for proper immune function: zinc, vitamin C, vitamin A, vitamin E, vitamins B2, B6 and B12, selenium, iron, copper, folate [1,2]
   
2. Increased Inflammation
   
   Inflammation is a normal part of your bodies healing function and is a sign your immune system is fighting something [1,3]. Chronic inflammation and regular intake of inflammatory foods can put your immune system into a heightened state, draining it of resources and limiting its ability to function correctly [4].
   
3. Refined Carbohydrates
   
   Refined carbohydrates such as pasta, white bread, pastry, some cereals are some inflammatory foods. These foods have a high glycaemic index and cause spikes in your blood sugar levels which contribute to inflammation in your body [5]
   
4. High Sugar Foods
   
   High sugar diets (especially from sugar sweetened drinks) are also inflammatory, and they provide a food source for unwanted bacteria [5]. Sugar also competes with vitamin C for entry into your immune cells.
   
5. Red and processed meat, margarine and dairy
   
   Red meat are high in saturated fats and inflammatory omega 6 [5]. Processed meat contain preservatives, colourings and artificial flavours all which are seen as foreign by your body, activating your immune response. Margarine [5], and full-fat dairy are also high in saturated fats.
   
6. High omega 6 to omega 3 ratio
   
   An excess omega 6 can put your body into a pro-inflammatory state [6]. Vegetable oils such as sunflower, grapeseed, peanut oil, mayonnaise and many salad dressings.
   
7. Alcohol
   
   Alcohol increases the burden on your liver leading to reduced detoxification and inflammation. Alcohol has also been shown to reduce good bacteria in the gut [7].
8. Reduced intake of fruit and vege intake
   
   The micronutrients needed for a healthy immune system are found only in fruits and vegetables; low intake in fruits and vegetables can impact the function of your immune system.
   
   Non-organic fruit and vegetables have pesticides on them that can alter the microflora of your digestive system which can lead to activation of your guts immune system.
   
9. Gluten
   
   This can be an issue for some people. During digestion, gluten can trigger zonulin, a protein which regulars the tight junctions of endothelial cells [8]. This can be one of the causes of leaky gut; a state of increased permeability of the intestines, which allows undigested food and harmful substances to enter your bloodstream. This, in turn, activates your immune system, causing it to go into a heightened state, using up vital resources
   
10. Too much coffee and black tea
    
    
    

Immune-boosting foods

1. Water
   
   Water is needed to remove waste and to aim proper elimination, and to transport minerals in and out of cells.
   
2. Vitamin A
   
   Vitamin A enhances white blood cell which destroy harmful bacteria and viruses: sweet potato, carrots, egg yolk, tomatoes, rockmelon, apricots, mangoes, pumpkin, spinach.
   
3. Vitamin C
   
   Vitamin C supports the function of the immune system by enhancing epithelial barrier function, enhancing the destruction of pathogenic microbes, clearing spent neutrophils, and enhancing the proliferation of B- and T- cells [9]. Blackcurrent, guava, blackberries, red capsicum, parsley, cabbage, watercress, strawberries, papaya, rockmelon, broccoli, cauliflower, snowpeas.
   
4. Flavonoids
   
   Flavonoids have antioxidant, anti-inflammatory, and anti-histamine benefits. : onions, berries, cherries [5], oranges, green tea, oolong tea.
   
5. Vitamin D
   
   Stimulates monocytes, macrophages, and neutrophils in the innate immune system, while also activating T- and B cells [10]. Herring, sardines, egg yolk.
   
6. Zinc
   
   Zinc is needed for proper development and function of lymphocytes and natural killer cells [10,11]. Zinc is also needed to counteract the inflammatory process [11]. Oysters, nuts like Brazil, almond, cashew, chestnut, pecans, pine and walnut, chicken, turkey, eggs, tahini, sunflower seeds, pumpkin seeds, parsley, spinach, mushrooms, butter beans, broad beans.
   
7. Omega 3
   
   Omega 3 rich foods have an anti-inflammatory action by reducing interleukin-1B and tumour necrosis factor-alpha [10]. Salmon, tuna, mackerel, walnuts, ground flaxseeds, chia seeds, soy beans.
   
8. Mushrooms
   
   Traditionally mushrooms have been used to modulate immune function. Think goldilocks and the porridge; you don’t want your immune system to be over- or under-active, but just right.
   
9. Herbs and Spices
   
   Not only do they add flavour to your food, they can have antioxidant, anti-inflammatory, antibacterial, and antiviral properties.
   
10. Wholegrains, beans, legumes and pseudo-grains
    
    They have a lower glycaemic index and are high in fibre which helps to feed the good bacteria in your gut.
    
11. Green tea
    
    Green tea is a good alternative to coffee. The caffeine in green tea is balances by theanine, giving you your coffee hit without the negative side effects. Green tea is also an antioxidant [12] and anti-inflammatory [9].
    
    

Lifestyle factors to boost your immune system

1. Get enough sleep
   
   Ensure both the quantity and quality of your sleep is right and hat you wake feeling refreshed [2].
   
2. Be active
   
   30-60 mins of moderate exercise most days of the week [2].
   
3. Maintain a healthy weight
   
   Excess weight can increase the burden on your body and increase inflammation [2,13].
   
4. Stress less
   
   Stress can cause a rise in your cortisol levels, which can lead to problems with your sleep. Cortisol is also shown to decrease the activity of your immune system by putting your body into a state of sympathetic dominance, increasing your fight or flight systems and decreasing the activity of your digestion system and other parasympathetic functions.
   
   
   
   
   

References:

[1] Maggini, S., Pierre, A., & Calder, P. C. (2018). Immune Function and Micronutrient Requirements Change over the Life Course. Nutrients, 10(10), 1531. https://doi.org/10.3390/nu10101531

[2] Harvard Medical School (2020). How to boost your immune system. Harvard Health Publishing. Retrieved from https://www.health.harvard.edu/staying-healthy/how-to-boost-your-immune-system 

[3] Taams L. S. (2018). Inflammation and immune resolution. Clinical and experimental immunology, 193(1), 1–2. https://doi.org/10.1111/cei.13155

[4] Leliefeld, P. H., Wessels, C. M., Leenen, L. P., Koenderman, L., & Pillay, J. (2016). The role of neutrophils in immune dysfunction during severe inflammation. Critical care (London, England), 20, 73. https://doi.org/10.1186/s13054-016-1250-4

[5] Harvard Medical School (2018). Foods that fight inflammation. Harvard Health Publishing. Retrieved from https://www.health.harvard.edu/staying-healthy/foods-that-fight-inflammation 

[6] Simopoulos A. P. (2016). An Increase in the Omega-6/Omega-3 Fatty Acid Ratio Increases the Risk for Obesity. Nutrients, 8(3), 128. https://doi.org/10.3390/nu8030128

[7] Bishehsari, F., Magno, E., Swanson, G., Desai, V., Voigt, R. M., Forsyth, C. B., & Keshavarzian, A. (2017). Alcohol and Gut-Derived Inflammation. Alcohol research : current reviews, 38(2), 163–171.

[8] Sturgeon, C., & Fasano, A. (2016). Zonulin, a regulator of epithelial and endothelial barrier functions, and its involvement in chronic inflammatory diseases. Tissue barriers, 4(4), e1251384. https://doi.org/10.1080/21688370.2016.1251384

[9] Carr, A. C., & Maggini, S. (2017). Vitamin C and Immune Function. Nutrients, 9(11), 1211. https://doi.org/10.3390/nu9111211

[10] Wu, D., Lewis, E. D., Pae, M., & Meydani, S. N. (2019). Nutritional Modulation of Immune Function: Analysis of Evidence, Mechanisms, and Clinical Relevance. Frontiers in immunology, 9, 3160. https://doi.org/10.3389/fimmu.2018.03160

[11] Wessels, I., Maywald, M., & Rink, L. (2017). Zinc as a Gatekeeper of Immune Function. Nutrients, 9(12), 1286. https://doi.org/10.3390/nu9121286

[12] Du, L. L., Fu, Q. Y., Xiang, L. P., Zheng, X. Q., Lu, J. L., Ye, J. H., Li, Q. S., Polito, C. A., & Liang, Y. R. (2016). Tea Polysaccharides and Their Bioactivities. Molecules (Basel, Switzerland), 21(11), 1449. https://doi.org/10.3390/molecules21111449

[13] Pinti, M., Appay, V., Campisi, J., Frasca, D., Fülöp, T., Sauce, D., Larbi, A., Weinberger, B., & Cossarizza, A. (2016). Aging of the immune system: Focus on inflammation and vaccination. European journal of immunology, 46(10), 2286–2301. https://doi.org/10.1002/eji.201546178