No nutrient functions alone in the body. Although one nutrient may be the main factor necessary for a particular reaction to occur, many reactions also require cofactors, or helper molecules in order to function properly. While some one-ingredient nutritional supplements can be an excellent addition to your diet, you won’t get the full benefit unless your diet is plentiful in all of the cofactors that nutrient needs to do its jobs. There also may be a different assortment of cofactors needed for the absorption of a nutrient, the availability of the nutrient for use, and the magnification of a nutrient’s action. 

For example, vitamin D plays a direct role in many biochemical pathways, but magnesium is required for eight different steps in the metabolism of vitamin D [1]. You can take a very high dose of vitamin D, but without enough magnesium in the diet, vitamin D cannot support your bone health, immune system, or mood. Depending on which biological pathway vitamin D is acting in, it may also require vitamin K, zinc, boron, and/or vitamin A (among others) for maximum efficiency [1].

Nutrition and Immunity

The immune system is made up of a complex network of cells, tissues, and organs. All of these body structures work together to defend against invaders such as viruses and bacteria. Your skin and mucous membranes are designed to keep germs out. When pathogens do get in, your body makes acids, enzymes, antibodies, lymphocytes, and other scavenger cells to find and destroy them before they cause damage. 

To make the immune cells and secretions, your immune system relies heavily on the nutrients delivered by your diet. This relationship becomes even more important when your body is under pathogenic attack and production must increase. Foods rich in vitamin C, like bell peppers or citrus, are a classic recommendation when you’re feeling under the weather. This is because vitamin C works as a cofactor in many of the pathways involved in immune system function. Vitamin C is far from alone as an immune response cofactor, however. 

Which nutrients are important immune system cofactors?

There are many nutrients that are critical cofactors in processes specific to immune function. Here, we will describe some of the heavy hitters. 

Vitamin C

As mentioned, vitamin C is fairly well-known as an immune-boosting vitamin. Its mechanism of action as a cofactor, however, may be less commonly understood. Vitamin C is a required cofactor for the movement of neutrophils (white blood cells) to an infection site, and for the engulfment and breakdown of pathogens [2]. It also participates in pathways that protect tissue from excessive damage by supporting the breakdown and removal of spent immune cells once they have finished their job [2]. The more invaders present, the more vitamin C your body needs to fight them.


Zinc has a complex role in the immune system. It has direct effects on immune response, acts as a cofactor for more than 300 enzymes, and can slow inflammation [3]. Zinc is essential for DNA synthesis and cell proliferation, so new immune cells created in response to infection are dependent on zinc.


Magnesium plays a role in hundreds of biological pathways within the body, a number of which are directly involved in immune response. Magnesium is a cofactor for the synthesis of immunoglobulins, the class of proteins also known as “antibodies”, which search and destroy specific pathogens [4]. Magnesium is a cofactor for C’3 convertase, an enzyme that is integral to the innate immune system and the release of inflammatory peptides [4]. It is also a cofactor for immune cell adherence, antibody-antigen binding, and antibody-dependent breakdown of pathogens, macrophage response to its activators, T helper-B cell adherence, binding of substance P to lymphoblasts, and antigen-binding to macrophage RNA [4]. There is evidence that magnesium deficiency leads to a weakened immune system, presenting in a number of ways [4]. 


Iron is essential for the formation of hemoglobin in red blood cells and the transport of oxygen throughout the body. Iron also serves as a cofactor to enzymes in oxidation/reduction reactions which allow for cellular energy metabolism. Low iron levels diminish immune response as it is required for immune cell production and growth [5]. Iron is particularly important for the development of new lymphocytes and therefore initiation of immune response to infection [5].


  1. Vitamin D Council. “Vitamin D and other vitamins and minerals.” copyright 2019.
  2. Carr, Anitra C., and Silvia Maggini. “Vitamin C and immune function.” Nutrients 9.11 (2017): 1211.
  3. Rink, Lothar. “Zinc and the immune system.” Proceedings of the Nutrition Society 59.4 (2000): 541-552.
  4. Galland, L. “Magnesium and immune function: an overview.” Magnesium 7.5-6 (1988): 290.
  5. Soyano, A and M Gómez M. “Role of Iron in Immunity and Its Relation With Infections”  Arch Latinoam Nutr 49(3 Suppl 2; 2008):40S-46S [Online]