Dietary supplement
According to US & Canadian Dietary Reference Intake guidelines, the protein Recommended Dietary Allowance (RDA) for adults is based on 0.8 grams protein per kilogram body weight. The recommendation is for sedentary and lightly active people. Scientific reviews can conclude that a high protein diet, when combined with exercise, will increase muscle mass and strength, or conclude the opposite. The International Olympic Committee recommends protein intake targets for both strength and endurance athletes at about 1.2-1.8 g/kg body mass per day. One review proposed a maximum daily protein intake of approximately 25% of energy requirements, i.e., approximately 2.0 to 2.5 g/kg.
Vegetarian and vegan dog diet
A good source of protein provides a dog with a balanced and complete profile of amino acids, and is essential for growth, muscle maintenance, and various cellular functions. Conventionally, these amino acids are primarily provided through either a singular or a combination of animal meats, meals, and by-products. A vegan diet provides the same amino acids through plants such as legumes, peas, beans, nuts, seeds and grains. While all plants contain some amount of protein, some plant sources contain more than others. However, plant sources generally do not have as complete an amino acid profile, as they are often limiting in one or more essential amino acids.  Good sources of plant protein include chickpeas, green peas, soybeans, potatoes, rice, lentils, beans, and quinoa. In dog food, the protein composition can be sourced from a variety of ingredients, including grains, rice, corn, wheat, and/or barley. Soybeans, one of the most common plant-based protein sources in dog foods, provide a concentrated and complete protein source, meaning that they provide all the essential amino acids in adequate amounts. If soy is excluded for hypoallergenic purposes, chickpeas, green peas, rice, and potatoes are also common ingredients in commercial vegan dog foods. Nutritional yeast is another good source of complete protein, and can also be added to complement the amino acid profile.