Which vitamin is crucial for vision and immune function?

Vitamin A is essential for maintaining proper vision and supporting the immune system. It plays a vital role in the process of vision, particularly in the formation of rhodopsin, a pigment in the retina that is crucial for low-light and color vision. A deficiency in vitamin A can lead to night blindness and other visual impairments.

Additionally, vitamin A contributes to the body's immune defenses by supporting the health of epithelial tissues, which act as barriers against pathogens, and by promoting the function of white blood cells, which are essential for fighting infections.

While other vitamins like C, D, and E have their respective roles in the body—such as antioxidant properties in the case of vitamin E and bone health linked to vitamin D—they do not play the same critical roles in vision and immune function as vitamin A does.