Vitamin D is on a roll these days. We have long known that the sunshine vitamin is critical for bone and muscle health. Ongoing research reveals that vitamin D may also support a wide array of functions and have health benefits that go beyond this classic role in bone development. For example, it is known to regulate immunity, support heart functions and reduce inflammation. Recently, a lot of studies have come out suggesting that vitamin D may help lower the risk of upper respiratory infections, asthma and allergies in both adults and children.