Vitamin D promotes intestinal calcium and phosphorous absorption and reduces urinary calcium loss, essential mechanisms for maintaining proper calcium levels in the body and for healthy bone composition. Research indicates that it also promotes cellular health, including support for breast and prostate tissue, in part by helping to maintain healthy blood vessel function, supporting immune cell activity, and maintaining healthy cell metabolism. A role for vitamin D in supporting colon health by promoting healthy cellular function has also been suggested. Vitamin D's role in immune health has long been established; vitamin D receptors are found on a number of immune cells, including lymphocytes and macrophages, supporting healthy immune cell activation. Vitamin D also supports cardiovascular function in some individuals.