Dietary Protein Quality and Requirements
The density of protein in a food source can be quantified on the basis of the amount of total calories ingested to achieve intake of the daily requirement of all EAAs. Non-protein components of protein food sources can be considered in terms of the amount and nature of fat, carbohydrate and fiber, as well as the content of micronutrients.
As a rule of thumb, anything over 100 on the DIAAS scale is a quality protein source.
The protein number itself does not tell the entire story, as different protein sources may be composed of vastly different amino acid ratios. In the case of a vegetarian or vegan diet for instance, the protein number may be adequate, but individual amino acids may be in lesser supply. This generally necessitates either individual amino acid supplementation or an overall increase in amount of ingested plant based protein to achieve the same results as an equivalent source of animal based protein.
Additionally: one of the main constituents of protein to consider when athletic performance (strength, power, hypertrophy) is important is Leucine content.
Free Form Aminos vs Intact Dietary Protein
Do not, however, confuse the importance of Leucine for an equivalence of whole protein and free form amino acids. Jackman et al found: “ingesting of all three BCAAs alone, without concurrent ingestion of other EAA, protein, or macronutrients, stimulated a 22% greater response of myofibrillar-MPS following resistance exercise compared with a placebo. The magnitude of this increased response of myofibrillar-MPS was ~50% less than the previously reported myofibrillar-MPS response to a dose of whey protein containing similar amounts of BCAAs. Taken together, these results demonstrate that BCAAs exhibit the capacity to stimulate myofibrillar-MPS, however a full complement of EAA could be necessary to stimulate a maximal response of myofibrillar-MPS following resistance exercise.” Even this does not tell the whole story as there are other constituents of dietary proteins that provide benefits beyond free form amino acids. This is why one could not simply take an EAA supplement to meet their daily protein needs.
Focusing only on MPS as an end proxy is methodologically unsound. One cannot ignore MPB or the requirement of other LBM (about 60% of one’s total protein use).
Because of this, the commonly accepted “25-30 grams per meal maximizing MPS” and the recommendation for 1.6 g/kg per day as optimal are potentially under-estimations.