 This has led to a general criticism that experiments on rats lead to an over-estimation of the BV of high-quality proteins to man because human requirements of essential amino acids are much lower than those for rats (as rats grow at a much faster rate than humans).Also, because of their fur, rats are assumed to have relatively high
requirements of sulphur-containing amino acids (methionine and cysteine).As a result, the analytical method that is universally recognized by the Food and Agriculture Organization (FAO), World Health Organization (WHO), the U.S. Food and Drug Administration (FDA), the United States Department of Agriculture (USDA), United Nations University (UNU) and the United States National Academy of Sciences when judging the quality of protein in the human is not PER or BV but the Protein Digestibility Corrected Amino Acid Score (PDCAAS), as it is viewed as accurately measuring the correct relative nutritional value of animal and vegetable sources of protein in the diet.