References:
1. Maggini et al. 2017, “Vitamin C, D and Zinc: Synergistic Roles in Immune Function and Infections”, Vitamins and Minerals.
2. Maggini S . 2008, “Feeding the immune system: the role of micronutrients in restoring resistance to infections”, CAB Reviews: Perspectives in Agriculture, Veterinary Science, Nutrition and Natural Resources , vol. 3: 98.
3. Rondanelli et al. 2018, “Self care for common colds : The Pivotal Role of Vitamin D, Vitamin C, Zinc, and Echinacea in Three Main Immune Interactive Clusters (Physical Barriers, Innate and Adaptive Immunity) involved during an episode of Common colds), practical advice on dosages and on the time to take these nutrients / botanicals in order to prevent or treat common colds”, Evidence-based complementary and alternative medicine
4. Ohio State University 2013, “Zinc helps fight against infection by tapping brakes in immune response”, https://www.sciencedaily.com/releases/2013/02/130207131344.htm#:~:text=Zinc%20helps%20against%20infection%20by%20tapping%20brakes%20in%20immune%20response,-Date%3A%20February%207&text=Summary%3A,be%20damaging%20and%20even%20deadly.
5. World Health Organisation 2002, “Childhood and maternal undernutrition”, https://www.who.int/whr/2002/chapter4/en/index3.html#:~:text=Using%20food%20availability%20data%2C%20it,throughout%20the%20world%20(13).
6. Black, R.E 2001, “Zinc deficiency, Immune Function, and morbidity and mortality from infectious diseases among children in developing countries”, Food and Nutrition Bulletin, vol. 22 (2)
7. healthline.com/nutrition/immune-boosting-supplements