Short answers, pulled from the story.
Proteins account for more mass in the human body than any molecule except water. They form the structural basis of hair, skin, blood, and bone while providing 17 kilojoules of energy per gram.
The nine essential amino acids that the human body cannot create are phenylalanine, valine, threonine, tryptophan, methionine, leucine, isoleucine, lysine, and histidine. Failure to ingest these nine leads to protein-energy malnutrition and eventual death.
The 2008 Chinese milk scandal involved adding the industrial chemical melamine to milk to inflate crude protein content measured by the Kjeldahl method. This fraud exploited the fact that melamine contains a high concentration of nitrogen, tricking testing equipment into reporting false protein values and causing kidney failure in thousands of infants.
The standard recommendation for a sedentary adult is 0.8 grams of protein per kilogram of body weight. Athletes engaging in endurance or strength training may require up to 2.0 grams per kilogram to repair muscle tissue and replace amino acids lost during exercise.
Protein deficiency, known as protein-energy malnutrition, accounts for 6 million deaths annually and can lead to conditions like kwashiorkor characterized by apathy, diarrhea, and edema. This condition affects over 10 million children in developing countries and is predominantly seen in hospitals and among the elderly in the industrialized world.