What is Vitamin A and What Does It Do?

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Our immune system relies on a wide network of actions to protect our body from disease and help promote healing. Several nutrients play important roles in immune function, and one of these essential players is Vitamin A.

What is Vitamin A?

Vitamin A is most widely known as promoting healthy vision, yet it also is essential for cell growth and differentiation and plays a critical role in the normal formation and maintenance of the heart, lungs, kidneys, and other organs. Vitamin A is actually the name of a group of fat-soluble retinoids that include retinol, retinal and retinyl esters. 

What is Vitamin A’s role in the Immune System?

Vitamin A insufficiency is associated with increased mortality to common gastrointestinal and lung infections and poor responses to vaccines.

Vitamin A plays a crucial role in the epithelium, which is the lining of the inside of our digestive tract as well as our skin that protects our entire body.

Vitamin A is also an important part of the immune function of the mucus layer of the respiratory tract and intestines.

T-cells are part of our body’s immune defense system responsible for killing infected cells and activating and regulating other immune responses. Retinoic acid (RA), a major oxidative metabolite of vitamin A, is a crucial component of T-cells. A review article published in the American Journal of Clinical Nutrition in 2012 concluded that although data from human studies are still needed, research from mice and rat models suggests that adequate vitamin A status, from either preformed retinol or beta-carotene, is important for maintaining a proper balance of well-regulated T cell functions and for preventing excessive or prolonged inflammatory reactions.

Find out more about Vitamin A!

By Lynn Grieger, RDN, CDCES, CPT, CHWC


  1. National Institutes of Health, Office of Dietary Supplements, Vitamin A Fact Sheet for Health Professionals. https://ods.od.nih.gov/factsheets/VitaminA-HealthProfessional/ updated 2-14-20, accessed 5-22-20
  2. Zhiyi Huang, Yu Liu, et al. Role of Vitamin A in the Immune System. J Clin Med. 2018 Sep; 7(9): 258.
  3. Ross AC. Vitamin A and retinoic acid in T cell-related immunity. Am J Clin Nutr. 2012;96(5):1166S?72S. doi:10.3945/ajcn.112.034637
  4. J.A. Hall et al. Essential role for retinoic acid in the promotion of CD4+ T cell effector responses via retinoic acid receptor alpha. Immunity. 2011 Mar 25; 34(3): 435–447.
  5. Milk Facts. http://www.milkfacts.info/Milk%20Composition/VitaminsMinerals.htm accessed 5-24-20.
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