Editorial by Dr. Seiji Aoyagi
NiHTEK’s Chief Science Officer (CSO)
- Leading PhD, most famous and respected PhD in sports nutrition research and science in Japan.
- Chief Science Officer (CSO) for DNS, Japanese largest Sports Nutrition manufacture and brand.
- Will help lead University studies in Japan and the leading spokesman to the Japanese market for NiHTEK®.
The International Society of Sports Nutrition (ISSN) For building muscle mass and for maintaining muscle mass through a positive muscle protein balance, an overall daily protein intake in the range of 1.4–2.0 g protein/kg body weight/day (g/kg/d) is sufficient for most exercising individuals1. However, it is not easy to consume enough protein from regular meals. Hence, use of protein supplements is highly recommended. Furthermore, ISSN recommends use of a high-quality protein1.
What does it mean by a high-quality protein for muscle protein synthesis (MPS)? It is rapidly digested proteins that contain high proportions of essential amino acids (EAAs) and adequate leucine, are most effective in stimulating MPS.
How then quantify protein quality? The concept of amino acid score is a physiologically relevant method to determine the protein quality. The classic method simply looks at the fulfillment of each EAA in a particular protein against requirements, the old barrel analogy. However, that does not consider protein digestibility. You are not what you eat, but you are what you digest and absorb.
In 1993, a new amino acid scoring system was developed. It is called Protein digestibility-corrected amino acid score (PDCAAS), a method of evaluating the quality of a protein based on both the amino acid requirements and their digestibility3.
However, the major fault of PDCAAS is that it looks at the fecal protein digestibility. Amino acids past the terminal small intestine (ileum) in the digestive system are less likely to be absorbed and subjected to bacterial digestion. Therefore, fecal digestibility over-estimates true protein digestibility by human. Also, PDCAAS caps at 1.0, making higher quality proteins indistinguishable to each other (Table 1).
More sophisticated amino acid score which is more true reflection of the human digestion was developed in 2013. It is called Digestible Indispensable Amino Acid Score (DIAAS)4. Instead of fecal digestion, DIAAS looks at the ileal digestion of each EAA and the fulfillment of human EAA requirements set by FAO for different age groups. Furthermore, DIAAS does not cap at 1.0. Therefore, the proteins with PDCAAS score of 1.0 can be properly put in the order of superiority in protein quality (Table 1).
References
- Jager R et al. JISSN (2017)14:20
- Dodd SAS et al. JAVMA (2018) 253(11);1425-1432
- FAO/WHO (1991) FAO Food and Nutrition Paper 51
- FAO/WHO (2013) FAO Food and Nutrition Paper 92
- Wathanavasin W et al. Asian Biomed (2024) 18(1);2-10
