NOW Foods D-Mannose Powder provides you with this carbohydrate in an easily usable powder format. D-Mannose is a simple sugar that occurs naturally in some plants, including cranberries. Although small amounts of D-Mannose are metabolized by the human body, much of it is rapidly excreted in the urine. In the bladder, D-Mannose may adhere to undesirable foreign substances, preventing them from sticking to the lining of the bladder. D-Mannose is by far the most effective supplement for both treatment and prevention of UTIs.