The digestion of some high-protein foods such as red meat, beans, lentils, and shell-fish, releases uric acid, HC5H3N4O3(aq), which ionizes into hydrogen ions, H+(aq) and urate ions, C5H3N4O3-(aq) in the bloodstream. People whose kidneys do not function properly cannot excrete urate ion sufficiently quickly, leading to an increased concentration of urate in the blood. This sometimes leads to a painful form of arthritis known as gout, characterized by the formation of tiny needle-like crystals of sodium urate, NaC5H3N4O3(aq), in joints and tissues according to the equation: