Low-protein diet
The daily requirement for humans to remain in nitrogen balance is relatively small. The median human adult requirement for good quality protein is approximately 0.65 gram per kilogram body weight per day and the 97.5 percentile is 0.83 grams per kilogram body weight per day. Children require more protein, depending on the growth phase. A 70 kg adult human who was in the middle of the range would require approximately 45 grams of protein per day to be in nitrogen balance. This would represent less than 10% of kilocalories in a notional 2,200 kilocalorie ration. William Cumming Rose and his team studied the essential amino acids, helping to define minimum amounts needed for normal health. For adults, the recommended minimum amounts of each essential amino acid varies from 4 to 39 milligrams per kilogram of body weight per day. To be of good quality, protein only needs to come from a wide variety of foods; there is neither a need to mix animal and plant food together nor a need to complement specific plant foods, such as rice and beans. The notion that such specific combinations of plant protein need to be made to give good quality protein stems from the book "Diet for a Small Planet". Plant protein is often described as incomplete, suggesting that they lack one or more of the essential amino acids. Apart from rare examples, such as Taro, each plant provides an amount of all the essential amino acids. However, the relative abundance of the essential amino acids is more variable in plants than that found in animals, which tend to be very similar in essential amino acid abundance, and this has led to the misconception that plant proteins are deficient in some way.
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.