Which vitamin is critical for vision and immune function?

Vitamin A is crucial for vision and immune function due to its role in various physiological processes. It is a key component of rhodopsin, a protein found in the retina that enables the eyes to adjust to low light levels, thus playing an essential role in night vision. Additionally, Vitamin A contributes to the maintenance of healthy epithelial (skin and mucous membrane) tissues, which serve as barriers against pathogens, supporting the immune system's ability to fight infections.

Furthermore, Vitamin A is involved in the regulation of immune responses, helping to maintain various immune functions such as the development of lymphocytes, which are critical for adaptive immunity. Deficiencies in Vitamin A can lead to significant visual impairments and increased susceptibility to infections, highlighting its importance for both vision and immune health.

In contrast, other vitamins like B12, D, and C have distinct roles in the body, such as assisting in energy metabolism, bone health, and antioxidant functions, but they do not specifically provide the same critical benefits for vision and immune function that Vitamin A does.