Which vitamin is commonly associated with improving immune function?

Vitamin A plays a crucial role in improving immune function due to its pivotal role in the proper functioning of the immune system. It helps maintain the integrity of skin and mucosal cells, which act as barriers against pathogens. Furthermore, vitamin A is essential for the production and activity of white blood cells, including lymphocytes, which are vital for the immune response.

While other vitamins such as D and B12 contribute to overall health and have roles related to immunity, vitamin A has a more direct and well-documented role in the enhancement of immune defenses. Vitamin D, for instance, also supports immune function, particularly in modulating the immune response and preventing excessive inflammation, but vitamin A is particularly noted for its importance in the early stages of infection response. Similarly, vitamin K has roles in blood clotting and bone health but does not have a direct impact on immune enhancement.