Proponents claim that chelation therapy is effective against atherosclerosis, coronary heart disease, and peripheral vascular disease. Its supposed benefits include increased collateral blood circulation; decreased blood viscosity; improved cell membrane function; improved intracellular organelle function; decreased arterial vasospasm; decreased free radical formation; inhibition of the aging process; reversal of atherosclerosis; decrease in angina; reversal of gangrene; improvement of skin color, healing of diabetic ulcers. Proponents also claim that chelation is effective against arthritis; multiple sclerosis; Parkinson's disease; psoriasis; Alzheimer's disease; and problems with vision, hearing, smell, muscle coordination, and sexual potency. None of these claimed benefits has been demonstrated by well-designed clinical trials.