Zinc
Zinc is described as an essential trace element [7] because only minimal amounts of the mineral are necessary for human health. It helps with the production of new immune system cells. Excellent sources of zinc include oysters, crab, chicken, turkey, baked beans, and yogurt. Zinc improves metabolism function, allows wounds to heal faster, and improves the sense of taste and smell.
It is best to source all your vitamins and minerals from natural foods. However, where you are unable to achieve the recommended daily intake through food, your doctor may prescribe supplementation.
References:
[1] https://www.betterhealth.vic.gov.au/health/conditionsandtreatments/immune-system
[2] https://health.clevelandclinic.org/eat-these-foods-to-boost-your-immune-system/amp/
[3] https://www.medicalnewstoday.com/articles/320101
[4] https://www.healthline.com/nutrition/vitamin-c-benefits
[5] https://www.healthline.com/nutrition/vitamin-a-benefits
[6] https://www.hsph.harvard.edu/nutritionsource/folic-acid/
[7] https://www.webmd.com/vitamins/ai/ingredientmono-982/zinc