Byte Sized Summary: a method estimating protein needs by amino acid consumption estimates that the recommended protein intake is too low.
While the method used in this study will not be accessible to most people, we did find it noteworthy that being deficient in single amino acid can waste a slew of others, and potentially inhibit uptake:
The indicator amino acid oxidation (IAAO) method is based on the concept that when 1 indispensable amino acid (IDAA) is deficient for protein synthesis, then all other IDAA, including the indicator amino acid, will be oxidized. With increasing intakes of the limiting amino acid, IAAO will decrease, reflecting increasing incorporation into protein. Once the requirement for the limiting amino acid is met, there will be no further change in the indicator oxidation. Originally, the IAAO method was designed to determine amino acid requirements in growing pigs. The minimally invasive IAAO method developed in humans has been systematically applied to determine IDAA requirements in adults. Due to its noninvasive nature, the IAAO method has also been used to determine requirements for amino acids in neonates and children, and in disease. The IAAO model has recently been applied to determine the metabolic availability (MA) of amino acids from dietary proteins and to determine total protein requirements. The IAAO method is robust, rapid, and reliable; it has been used to determine amino acid requirements in different species, across the life cycle, and in diseased populations. The recent application of IAAO to determine MA of amino acids and protein requirements is also very novel.
Importantly, the following statement (our emphasis):
…we examined the total protein requirement in adult humans using the IAAO method (36), as previously applied in young pigs (6). Graded intakes of a mixture of amino acids in the pattern present in egg protein, except phenylalanine, ranging from 0.1 to 1.8 g·kg−1·d−1, were fed and indicator amino acid (L-[1-13C]phenylalanine) oxidation was measured. The mean protein requirement was 0.93 g·kg−1·d−1 and is 41% higher than the current DRI recommendation.
That is from the Journal of Nutrition, full article here.
This was first brought to our attention by the folks at Ergo-Log.