In 1747 James Lind, referred to nowadays as “The Father of Naval Medicine” conducted an experiment on British sailors who were suffering from nasty bouts of scurvy, showing how eating lemons and limes reduced symptoms drastically. Indeed, scurvy is caused by a Vitamin C deficiency which sailors were experiencing due to a lack of fresh fruit and vegetables on their voyages. Lind’s experiment lead to the inclusion of limes as a staple in every sailor’s diet and subsequently birthed the nickname given to British sailors at the time… Limeys!
There are dozens of micronutrients (vitamins and minerals) which our body can’t synthesise in sufficient amounts and we must therefore obtain from our diets to avoid deficiency and subsequent health issues . Here we’ll look at three in particular, what the research says and how you can obtain them through your diet.
Involved in hundreds of biochemical reactions within your body, Vitamin B6 is necessary for proper immune function as it aids in the production of antibodies needed to help fight off infection . A deficiency of the vitamin can also impair production of Interleukin-2 which is a protein responsible for instructing white-blood cells during an immune response to bacteria or infection [3, 4].
Symptoms of a Vitamin B6 deficiency include low energy levels, skin rashes and sore/dry lips. The RDA for Vitamin B6 is 1.4/1.2mg per day for men/women. Plant based foods high in the vitamin include carrots, bananas and avocados.
Humans are unable to synthesise Vitamin C as we lack a specific enzyme involved in the biochemical pathway to create the nutrient  and indeed, Vitamin C deficiency was listed as the 4th most common micronutrient deficiency in the US in the Centre for Disease Control’s 2012 report . A deficiency in Vitamin C can lead to breakdown of epithelial barriers which protect from invading pathogens and through other mechanisms, can impair the capabilities of our immune system to destroy harmful bacteria .
Symptoms of deficiency include slow-healing wounds, bleeding gums and rough, damaged skin. [8-10] The RDA for Vitamin C is 90/75mg a day for men/women. As you might have guessed, limes are an excellent source of Vitamin C. If eating a lime a day isn’t your thing then you can also find ample amounts of the micronutrient in red pepper, oranges, kiwi, broccoli, strawberries and grapefruit.
Zinc is a multi-functional mineral in humans and plays a number of critical roles in our body - as a catalyst for enzymic reactions, in the development of cellular structures and in regulation the internal conditions of our body (homeostasis) . Zinc deficiency not only affects our innate immune system (the first line of defence against infection) through impaired white blood cell function, but also our acquired immune system (our ability to respond and fight off infection from previously encountered pathogens) . Put simply, without sufficient zinc, our bodies cannot create new healthy cells.
Symptoms include sores on the skin, loss of appetite and diarrhoea. The RDA for Zinc is 9.5/7mg for men/women. Unlike the other micronutrients we’ve looked at, fruit and veg are generally pretty poor sources of Zinc. Legumes, Nuts and Seeds are all good dietary sources.
The list of vitamins and minerals involved in our immune system is long and complex. However, hopefully you now have a basic insight into the importance of various micronutrients, not just for our immune system but for basic bodily functions. Ensuring your diet is varied and full of fruits and vegetables should keep you covered for most vitamins but ensure you’re aware of where you can obtain sufficient amounts of the less common nutrients such as Zinc which we discussed above.
1. Gombart, A.F., A. Pierre, and S. Maggini, A Review of Micronutrients and the Immune System-Working in Harmony to Reduce the Risk of Infection. Nutrients, 2020. 12(1).
2. Qian, B., et al., Effects of Vitamin B6 Deficiency on the Composition and Functional Potential of T Cell Populations. J Immunol Res, 2017. 2017: p. 2197975.
3. Meydani, S.N., et al., Vitamin B-6 deficiency impairs interleukin 2 production and lymphocyte proliferation in elderly adults. Am J Clin Nutr, 1991. 53(5): p. 1275-80.
4. Malek, T.R., The main function of IL-2 is to promote the development of T regulatory cells. J Leukoc Biol, 2003. 74(6): p. 961-5.
5. Nishikimi, M., et al., Cloning and chromosomal mapping of the human nonfunctional gene for L-gulono-gamma-lactone oxidase, the enzyme for L-ascorbic acid biosynthesis missing in man. J Biol Chem, 1994. 269(18): p. 13685-8.
6. Pfeiffer, C.M., et al., The CDC's Second National Report on Biochemical Indicators of Diet and Nutrition in the U.S. Population is a valuable tool for researchers and policy makers. J Nutr, 2013. 143(6): p. 938S-47S.
7. Carr, A.C. and S. Maggini, Vitamin C and Immune Function. Nutrients, 2017. 9(11).
8. Galimberti, F. and N.A. Mesinkovska, Skin findings associated with nutritional deficiencies. Cleve Clin J Med, 2016. 83(10): p. 731-739.
9. Olmedo, J.M., et al., Scurvy: a disease almost forgotten. Int J Dermatol, 2006. 45(8): p. 909-13.
10. Cosgrove, M.C., et al., Dietary nutrient intakes and skin-aging appearance among middle-aged American women. Am J Clin Nutr, 2007. 86(4): p. 1225-31.
11. Chasapis, C.T., et al., Zinc and human health: an update. Arch Toxicol, 2012. 86(4): p. 521-34.
12. Shankar, A.H. and A.S. Prasad, Zinc and immune function: the biological basis of altered resistance to infection. Am J Clin Nutr, 1998. 68(2 Suppl): p. 447S-463S.