The Great Vitamin-D Scam. Many lies and misconceptions surround this vitamin which is actually a hormone substance. Generally, most of us are deficient in this vitamin. We have been told to stay out of the sun yet we derive this important nutrient from the sun and it is needed daily! It plays a critical role in our immune function and our risk of many diseases including cancer. People should spend 15-20 minutes in the sun daily and longer for the darker skinned people. It must be done without sunscreen! Get your vitamin D3 level checked! You might be surprised.