Tinnitus Guard ReviewsFrom October until the end of March, the angle of the sun is such that, in much of North America, no vitamin D is available from that source," Lappe said. "What that means is most of us are deficient in vitamin D this time of year." The amount of vitamin D you should take daily is a subject of great debate, Lappe notes. While there may be a great deal of debate about how much vitamin D is needed for optimum health, there is little debate about how valuable Vitamin D is for human health. Without Vitamin D there would be no human life. Among a very long list of benefits associated with Vitamin D are prevention and treatment of: infections and inflammation, cancer prevention, depression and neurological disorders, cold and flu, diabetes, osteoporosis and tuberculosis.