Both Vitamin C and Vitamin A are important for immune system function, but they contribute in different ways.

Vitamin C:

1. Antioxidant Properties: Vitamin C is a potent antioxidant, which helps protect cells from damage caused by free radicals¹.
2. Support for Innate and Adaptive Immunity:
   • Supports cellular functions of both the innate and adaptive immune system².
   • Enhances chemotaxis, phagocytosis, and microbial killing in phagocytic cells (e.g., neutrophils)².
   • Aids in the differentiation and proliferation of B- and T-cells².
3. Epithelial Barrier: It helps maintain the integrity of the epithelial barrier against pathogens².
4. Infection Response: Deficiency in Vitamin C leads to impaired immunity and higher susceptibility to infections².

Vitamin A:

1. Epithelial Tissue Maintenance: Vitamin A is crucial for the formation and maintenance of epithelial tissues, which act as a barrier to pathogens³.
2. Innate Immunity:
   • It is involved in the differentiation and function of innate immune cells like macrophages³.
3. Adaptive Immunity:
   • Influences the maturation of T cells and the function of B cells³.
4. Cytokine Regulation: It helps regulate the production of inflammatory cytokines³.

Comparative Importance:

• Innate Immune Functions: Both vitamins support the innate immune system, but Vitamin C also plays a direct role in oxidative defense and enhancement of phagocytic abilities¹².
• Adaptive Immune Functions: Vitamin A has a more prominent role in the differentiation and maturation of T and B cells³.
• Barrier Integrity: While both vitamins help maintain epithelial integrity, Vitamin A is particularly critical for the maintenance and function of all epithelial tissues³.

Conclusion:

• Complementary Roles: Both vitamins are essential, providing complementary support to the immune system. The importance of one over the other might depend on specific health conditions and nutritional status.
• No Absolute Answer: It is not straightforward to declare one as more important than the other without context, as both have unique and critical roles in immune function.

Ultimately, a balanced intake of both vitamins is beneficial for a robust immune system.

Footnotes

1. Carr, Anitra C. Vitamin C and Immune Function. PubMed, 2017. Link ↩ ↩²

2. Office of Dietary Supplements. Dietary Supplements for Immune Function and Infectious Diseases. 2023. Link ↩ ↩² ↩³ ↩⁴ ↩⁵ ↩⁶

3. Mora, J. Rodrigo. Vitamin effects on the immune system: vitamins A and D take centre stage. PMC, 2024. Link ↩ ↩² ↩³ ↩⁴ ↩⁵ ↩⁶