The indicator amino acid oxidation technique (IAAO) is a new, more precise way of measuring individual amino acid and protein requirements of sedentary and active people. According to studies using this method, active people should consume 1.4 to 2 grams of protein per kilogram bodyweight per day, with guys who lift weights on the high end. The recommended daily allowance (RDA) established by the U.S. Department of Agriculture is 0.8 grams per kilogram bodyweight per day. These recommendations were based on 50 years of research on protein metabolism using a technique called nitrogen balance. Nitrogen is a component of protein that is discarded when proteins are broken down to amino acids and used for energy. Nitrogen balance involves measuring nitrogen output in feces, urine and sweat and comparing it with nitrogen intake in the diet. IAAO is a new and less messy technique that predicts whole-body protein requirements by measuring the metabolism of a labeled amino acid. Canadian scientists studied human protein requirements using IAAO and determined that the RDA for protein of 0.8 grams per kilogram bodyweight per day is too low and should be 1.2 grams per kilogram per day for sedentary people. IAAO shows that weight trainers were right all along – they need more protein than the basic RDA recommendation. (Current Opinion in Clinical Nutrition and Metabolic Care, 11:34-39, 2008; American Journal Clinical Nutrition, 86:995-1002, 2007)