When a team of scientists set out to explore how vitamin D influences the pediatric respiratory system after acute respiratory tract infections (ARTI), they were actually on a mission to review available literature to better understand vitamin D’s immunomodulatory and antiviral function.
An immunomodulator is a substance that modifies, or modulates, the immune system to help your body respond to a disease or illness.
Vitamin D is a crucial micronutrient found in foods and a hormone made by the body. It is associated with immune system functions. It is known to stimulate innate immunity, reduce the production of helper T lymphocytes (type 1), and improve the proliferation of regulatory and type 2 T lymphocytes.
Also, vitamin D helps decrease pro-inflammatory cytokines such as IL1, IL6, IL12, and TNFα, reduce interferon γ, and increase IL10 (anti-inflammatory cytokines) through the NFkβ metabolic pathway.
These immune cells play significant roles in children diagnosed with ARTI thus; upper respiratory tract infections (URTIs) and lower respiratory tract infections (LRTIs), most of which are associated with viral infections caused by rhinovirus, SARS-associated coronavirus, enterovirus, influenza virus, and respiratory syncytial virus.
Vitamin D’s antiviral functions
The group of scientists found a total of 518 citations after their search; with 27 of them fulfilling all inclusion criteria and hence were considered for the review.
They found out that a major circulating vitamin D form; 25(OH)D exhibits antiviral properties through antimicrobial peptides. They also established that calcitriol, which is an active vitamin D form, is crucial in limiting pathogenic presence.
They made the following facts;
- Vitamin D improves immunity by promoting monocyte differentiation, preventing lymphocyte production and enhancing the phagocytic activity of macrophages.
- A lower level of 25(OH)D enhances the risk of developing ARTI in children.
- A higher vitamin D concentration lowered the risk of recurring pneumonia.
Food Sources of Vitamin D
Only few sources of foods have been named by experts as naturally rich in vitamin D3. However, the best sources are the flesh of fatty fish and fish liver oils. Smaller quantities of Vitamin D are also found in egg yolks, cheese, and beef liver.
Additionally, certain mushrooms contain vitamin D2; as some mushrooms which are commercially sold are intentionally exposed to high amounts of ultraviolet light. Certain foods and supplements are also fortified with Vitamin D and they are;
- Cod liver oil
- Salmon
- Swordfish
- Tuna fish
- Orange juice fortified with vitamin D
- Dairy and plant milks fortified with vitamin D
- Sardines
- Beef liver
- Egg yolk
- Fortified cereal
Journal reference:
Nicolae, M. et al. (2023) “Immunomodulatory Effects of Vitamin D in Respiratory Tract Infections and COVID-19 in Children”, Nutrients, 15(15), p. 3430.