Vitamin D is another nutrient that the body needs for proper immune system function. Just like vitamin C, vitamin D plays a role in both the body’s innate and adaptive immune responses, but it’s also needed for bone health (which I won’t talk about in this post). Basics A few things to know about vitamin D in general before I dive into its effects on immunity. Vitamin D is a fat-soluble vitamin, and it is unique in that your body can make it. This is nice because natural food sources of Vitamin D are not that easy to find. Ultraviolet light triggers the production of vitamin D from a molecule derived from cholesterol, which then has to be converted by your liver to 25 hydroxy vitamin D, the storage form of this vitamin, and then activated by your kidneys to the active form. Similarly, Vitamin D from food has to…