This review, conducted by several Canadian and British research institutes, gives an overview of the beneficial effects of vitamin D on the regulation of immune function. Vitamin D showed, among others, a beneficial interaction with multiple processes executed by the immune system and several effects on immune cells. Moreover, vitamin D deficiency at a young age could predispose to immunological diseases and a malfunctioning immune system. Several studies showed that vitamin D supplementation could be a beneficial strategy for improving health, for instance, preventing bacterial and viral infections and decreasing the severity of these diseases. More details can be found in the review.
Bishop et al.