Micronutrients and Immune Function Made Simple by a Registered Dietitian

April 7 of each year marks the celebration of World Health Day! World Health Day is an annual day to celebrate and discuss the important health issues that impact us all. In honor of World Health Day, we brought in Tiffany Ma, Registered Dietitian, to discuss the ways you can keep yourself and your immune system important during this time. Continue reading below to find out more!

Micronutrients and Immune Function

Our bodies are smart, and oftentimes, we don’t recognize just really how intelligent they really are! All of what we can see is pretty much surface level; but the complexities and the inner-workings that occur on a cellular level is not one to be taken for granted.

Our immune system doesn’t have just ONE line of defense when it comes to defending our bodies; but up to three! When viral pathogens (things we don’t want) enter our bodies, we have three ways of reacting to it:

  1. Progressively build a barrier to prevent them from coming into the body in the first place
  2. Identify and eliminate them by digesting them
  3. Create a memory to prevent further invasions in the future (1)

Pretty, cool right?

Although everybody’s genetic make-up, as well as personal health are individualized and unique; one thing falls true—how we take care of our body has a significant contribution to our body’s overall immune system, which is what protects us in the first place. How we take care of our body includes the amount of rest we get, the amount of physical activity we participate in, and of course—the types of nutrients we provide our bodies with.

What is a Micronutrient?

Micronutrients are often referred to as vitamins and minerals, and they play an essential role in our health—whether that be development, prevention or treatment. Although many of us probably are more familiar with the term ‘Macronutrient’ (protein, carbs and fat)—micronutrients are as equally as important! We just need these nutrients on a smaller level; hence the name! (2)

Vitamin C

I bet this isn’t the first time you’re hearing about vitamin C, as it is often a micronutrient that we hear often when it comes to health and immunity. Vitamin C works mainly by building up the main first line of defense, which is the epithelial barrier in our bodies. As a powerful antioxidant, it also produces species in our bodies to defend against infection when it does occur. Vitamin C is naturally occurring in plenty of fruits and vegetables; such as citrus fruits, leafy greens like spinach, tomatoes and berries. The Recommended Daily Intake (RDI) of vitamin C is 100 to 200 mg. (3)

Vitamin D

Vitamin D—the underrated micronutrient when it comes to immune support. We often hear about vitamin D’s role in bone and joint health; but not when it comes to beating a cold. Recent studies have actually shown that vitamin D plays an important factor in protecting against viral infections. One meta-analysis, published in 2017, states vitamin D supplementation is able to provide a protective factor against acute respiratory tract infections. (5)

One key take-away about vitamin D that we can’t ignore—is that vitamin D deficiency is actually quite more common than we think. In fact, it’s estimated that about 1 billion people worldwide have low levels of vitamin D in their blood. With that being said, supplementation of this sunshine micronutrient would probably prove to be more useful than not. Foods rich in vitamin D include: oily fish, egg yolks, red meat, and fortified foods. If you’re looking to supplement with vitamin D, look for its most bioavailable form—which is vitamin D3, or cholecalciferol. Vitamin D dosing recommendations vary according to where you are in the country; but for most adults, aiming anywhere from 2,000 to 5,000 IU of vitamin D3 will be most helpful on a daily basis. (6)


Zinc also plays an important role in immune function by being responsible for not only developing macrophages and immunoglobulins, but by also responding to infection. We know that being deficient in zinc slows down the development of phagocytosis, which is just a fancy way of describing the body’s natural way to eat a cell that might be harmful to the body. If you’re not sure whether or not you’re getting enough zinc in the body, be sure to nourish it with plenty of lean meats, poultry, eggs, seafood, beans, lentils, seeds and nuts.

A daily low dosage of zinc can be taken on a daily basis; and is anywhere from 5 – 10 mg. If you have been diagnosed with a Zinc deficiency, it might be helpful to dose on the higher end, which is about 25 – 45 mg until you are no longer deficient. (7)

Bottom Line

Keeping yourself healthy during this time should be a priority for everybody at the time. Good nutrition through the consumption of fruits, vegetables, whole grains, legumes, lean proteins, and low-fat dairy is still important, regardless of what your supplement stack looks like! Be sure to consult with your physician before starting any dietary supplement!


  1. Günther J, Seyfert HM. The first line of defense: insights into mechanisms and relevance of phagocytosis in epithelial cells. Semin Immunopathol. 2018;40(6):555-565. doi:10.1007/s00281-018-0701-1
  2. Shenkin A. Micronutrients in health and disease. Postgrad Med J. 2006;82(971):559-567. doi:10.1136/pgmj.2006.047670
  3. Chambial S, Dwivedi S, Shukla KK, John PJ, Sharma P. Vitamin C in disease prevention and cure: an overview. Indian J Clin Biochem. 2013;28(4):314-328. doi:10.1007/s12291-013-0375-3
  4. Bailey DM, Williams C, Betts JA, Thompson D, Hurst TL. Oxidative stress, inflammation and recovery of muscle function after damaging exercise: effect of 6-week mixed antioxidant supplementation. Eur J Appl Physiol. 2011 Jun;111(6):925-36. doi: 10.1007/s00421-010-1718-x. Epub 2010 Nov 11. PMID: 21069377.
  5. Martineau AR, Jolliffe DA, Hooper RL, Greenberg L, Aloia JF, Bergman P, Dubnov-Raz G, Esposito S, Ganmaa D, Ginde AA, Goodall EC, Grant CC, Griffiths CJ, Janssens W, Laaksi I, Manaseki-Holland S, Mauger D, Murdoch DR, Neale R, Rees JR, Simpson S Jr, Stelmach I, Kumar GT, Urashima M, Camargo CA Jr. Vitamin D supplementation to prevent acute respiratory tract infections: systematic review and meta-analysis of individual participant data. BMJ. 2017

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