Human nutrition
The protein requirement for each individual differs, as do opinions about whether and to what extent physically active people require more protein. The 2005 Recommended Dietary Allowances (RDA), aimed at the general healthy adult population, provide for an intake of 0.8 grams of protein per kilogram of body weight. A review panel stating that "no additional dietary protein is suggested for healthy adults undertaking resistance or endurance exercise."
Puppy nutrition
Protein in excess of these levels is metabolized and leads to an increase of the glomerular filtration rate, and increased urea excretion in the urine, with no evidence of damage to the kidneys. However, addition of protein past these requirements is not recommended, although the NRC has not quantified a safe upper limit. Considering that the energy density of protein is similar to that of carbohydrates, an excess of protein in the diet may lead to fat deposition and weight gain. This excess weight can lead to abnormal joint development, potentially giving rise to joint issues in the future. Additionally, excess of some amino acids may also have detrimental impacts; for example, excess lysine will negatively antagonise arginine. The minimal requirement laid out by the NRC is 180g/kg (18%) DM of crude protein, with a recommended allowance of 225g/kg (22.5%) DM. With this in mind, it is also important to consider the quality and digestibility of the protein used.