Patients with diabetes have dysfunction of the lining of the arteries which lead to impaired circulation in the small blood vessels. This is thought to be secondary to reduced chemicals in the blood viz: nitric oxide. This chemical is derived from an amino acid (protein) L-arginine. Therefore, the researchers investigated whether giving patients L-arginine (versus dummy powder) would improve the blood flow in the small blood vessels in the lower limbs of patients with damage to their nerves (neuropathy).