Why Vitamin D Is Important Your immune system, blood cells, and bones are crucial for your body's fight against pathogens. Most of your vitamin D comes from exposure to sunshine on your skin. It should work with just a few minutes per day on your hands and face. However, food can also provide it. You might not get enough vitamin D if you're elderly, unwell, or housebound. If you believe that your levels are low, consult your doctor. What...