The Immune System Explained
What is the immune system?
Your immune system is your body’s defense mechanism against illness, and there are several powerful nutrients you can consume to strengthen it. The main contributor to the development of ailments is pathogens. These are highly reactive, uncharged molecules contributing to everything from the common cold to potential cancer or dementia.
Firstly though, lets briefly investigate the various components of the immune system and how it functions to protect you.
The Three Types of Immunity
1. Innate immunity
The innate system is the body’s first bastille against pathogens, functioning as the mucous linings of the throat and gut area, as well as the skin. The innate system operates as a protective physical and chemical barrier. If a pathogen can enter the body, cells called ‘Macrophages’ intervene and eliminate the harmful bacterium.
If the macrophages are unable to deal with the invaders, messenger proteins signal Neutrophils. These furiously fighting cells patrol the body, killing pathogens with toxins.
2. Adaptive Immunity
The adaptive immune system represents the next level of defense dealing with pathogens unable to be conquered by the innate system. The ‘Dendritic’ cells act as the link between the innate and adaptive systems. They carry information about a pathogen to the adaptive immune system cells, to create a tailored response.
The dendritic cells then travel to the nearest lymph node to find an appropriate lymphocyte (white blood cells) or ‘T-cell’ (another specific attack cell) to defeat the threat.
The dendritic cell is looking for the best matched T-cell with the correct makeup to combat the pathogens. Once the perfect T-cell is found, it is duplicated thousands of times. Some become memory T-cells remaining in the lymph node to fight future ailments. Others travel to the front lines to further the attack, while a third group activates another type of cell, B cells.
B-cells, once activated by T-cells, produce antibodies. Antibodies bind to the surface of the specific attacking pathogen. The billions of antibodies produced by the B-cells flood the body, directly dismantling and preventing the pathogens from doing further harm and enabling the aforementioned array of fighting cells to finally destroy the potential ailments. Memory T and B cells stay behind. These cells can recognize the same pathogen if it attacked again and instantly initiate a proper immune response.
Four Vital Immune Vitamins
1. Vitamin C
Ask anyone to name you a vitamin, and they’ll likely retort vitamin C. In the three-hundred years since its initial discovery by chemist Albert Szent-Györgyi, vitamin C has been found to have immeasurable health effects.
First and foremost, the water-soluble vitamin is a potent antioxidant, meaning it helps fight and balance the build-up of dangerous levels of free radicals.
The antioxidant activity of Vitamin C has a direct effect on lymphocytes. Studies have shown that vitamin C can improve the functioning of lymphocytes, enhancing their protective effects, and increasing their lifespan.
The nutrient has also been shown to have a positive effect on the specific illness as well. Research indicates regular intake of vitamin C can potentially decrease the duration of a cold by an average of 8% in adults and 14% in children with the severity of symptoms also being reduced. While other studies have linked vitamin C deficiency to significantly lowered immunity and higher susceptibility to infections.
The World Health Organization recommends 45mg of vitamin C a day, which can easily be found in foods such as guava, oranges, red bell pepper, spinach, and many other fruits and vegetables.
2. Vitamin D – The Sunshine Vitamin
Vitamin D is a potent fat-soluble immunological vitamin demonstrated to reduce respiratory tract infections. Supplementation resulted in a 19% reduction in bacterial and viral chest infections in those non-deficient in the nutrient, and a massive 70% reduction in those that were deficient.
This nutrient is also essential for the regeneration of the epithelial barrier, the protective lining between our cells from damage and infection. It plays a fundamental role in the maturation of the immune cells.
Vitamin D is aptly synonymous with the life-giving properties of the sun. Most of the daily requirements can be gained from sun exposure to the skin, though the vitamin is present in foods, also, such as fatty fish, egg yolk, and soy products. The World Health Organization recommends an age-dependent daily dose of 5mg for 19-50-year-olds, 10mg for 51-65, and 15mg at 65+.
3. Vitamin E
Vitamin E is an esteemed fat-soluble nutrient relating to the immune system. As an antioxidant, it is a potent free-radical fighter but also has many unique immunological properties. Vitamin E supplementation has been shown to reduce markers of decreased immunity seen in aging populations and in those with AIDS. It also influences the functioning of T-cells directly, through modulating cell division and structural integrity positively.
There is also evidence that vitamin E decreases susceptibility to respiratory infection, particularly in the elderly, with one trial showing a 60% reduction in infectious disease with over six months of supplementation.
While deficiencies are rare, vitamin E has very low toxicity, and supplementation of 100-200mg is widely used and deemed safe.
Foods high in vitamin E include almonds, peanuts, and hazelnut, as well as sunflower seeds and avocado.
4. Vitamin A
Vitamin A is a fat-soluble nutrient encompassing three essential fat-soluble molecules; retinol, retinal, and retinoic acid. Retinol is the form stored in the body, retinal is crucial for vision and retinoic acid functions much like a hormone, modulating the functions of hundreds of different genes.
Vitamin A contributes to immune function by augmenting T-cell proliferation and function, considerably boosting the overall health of your body. It is touted as one of the key nutrients involved crucial immunological mechanisms taking place in the GI tract, leading to immune tolerance across the entire gut lining.
The most bioavailable forms of vitamin A (meaning the ones that can be best digested and utilized by the body) come from eggs, cod liver oil, dairy, and fortified breakfast cereals, while other sources (though less bioavailable) can come from dark leafy vegetables like spinach and kale. The WHO recommends an intake of 270mg per day for 19-65-year-old females, and 300mg for males, with the recommended safe intake being 500mg for females and 600 for males.
Linden Garcia Pepworth is a Sports Nutritionist (BSc Sports Nutrition) and YMCA Accredited Instructor. He is currently working on a review comparing the anabolic differences between plant and animal proteins.
2. Florence, T. M. (1995). The role of free radicals in disease. Australian and New Zealand journal of ophthalmology, 23(1), 3-7.
3. Van Gorkom, G. N., Klein Wolterink, R. G., Van Elssen, C. H., Wieten, L., Germeraad, W. T., & Bos, G. M. (2018). Influence of vitamin C on lymphocytes: an overview. Antioxidants, 7(3), 41.
4. Hemilä, H., & Chalker, E. (2013). Vitamin C for preventing and treating the common cold. Cochrane Database of Systematic Reviews, (1).
5. Carr, A. C., & Maggini, S. (2017). Vitamin C and immune function. Nutrients, 9(11), 1211.
6. Martineau, A. R., Jolliffe, D. A., Hooper, R. L., Greenberg, L., Aloia, J. F., Bergman, P., ... & Goodall, E. C. (2017). Vitamin D supplementation to prevent acute respiratory tract infections: systematic review and meta-analysis of individual participant data. bmj, 356, i6583.
7. Assa, A., Vong, L., Pinnell, L. J., Avitzur, N., Johnson-Henry, K. C., & Sherman, P. M. (2014). Vitamin D deficiency promotes epithelial barrier dysfunction and intestinal inflammation. The Journal of infectious diseases, 210(8), 1296-1305.
8. Aranow, C. (2011). Vitamin D and the immune system. Journal of investigative medicine, 59(6), 881-886.
9. Meydani, S. N., & Hayek, M. G. (1995). Vitamin E and aging immune response. Clinics in geriatric medicine, 11(4), 567-576.
10. Wang, Y., & Watson, R. R. (1993). Is vitamin E supplementation a useful agent in AIDS therapy?. Progress in food & nutrition science, 17(4), 351-375.
11. Lewis, E. D., Meydani, S. N., & Wu, D. (2019). Regulatory role of vitamin E in the immune system and inflammation. IUBMB life, 71(4), 487-494.
12. MEYDANI, S. N., Han, S. N., & HAMER, D. H. (2004). Vitamin E and respiratory infection in the elderly. Annals of the New York Academy of Sciences, 1031(1), 214-222.
13. Freycon, F., & Pouyau, G. (1983). Rare nutritional deficiency anemia: deficiency of copper and vitamin E. La semaine des hopitaux: organe fonde par l'Association d'enseignement medical des hopitaux de Paris, 59(7), 488-493.
14. https://apps.who.int/ iris/bitstream/handle/10665/42716/ 9241546123.pdf?ua=1
15. Zhong, M., Kawaguchi, R., Kassai, M., & Sun, H. (2012). Retina, retinol, retinal and the natural history of vitamin A as a light sensor. Nutrients, 4(12), 2069-2096.
16. Ross, A. C. (2012). Vitamin A and retinoic acid in T cell–related immunity. The American journal of clinical nutrition, 96(5), 1166S-1172S.
17. https://www.clinicaleducation.org/ resources/reviews/vitamin-a-the-key-to-a- tolerant-immune-system/