As with all nutrients, our bodies need vitamin D from the environment (through food or sunlight in this case) to function properly. Vitamin D has a particularly important role in bone health by helping with calcium absorption. This is a very clear relationship as its classic deficiency symptoms are diseases of “soft bones” – rickets in children and osteoporosis and fractures in adults (Bilke DD, 2014). However, with the discovery of vitamin D receptors in virtually every type of cell in the body (Pludowski et al. 2018), we have found that vitamin D affects many other parts of the body, like the immune system (Ginde 2009) and the cardiovascular system (Michaelsson et al. 2010). This combination of health benefits may be why several studies have found that those with higher vitamin D blood levels live better for longer (Garland et al. 2014). So, we need vitamin D to build and keep our bones strong, but also to help the rest of our body work like it should.