A discussion on the ‘dispensable’ amino acids

Abstract

Purpose of review Recently, the concept of dietary dispensable amino acids has been increasingly challenged, as more indirect and direct (experimental) evidence has pointed to the need for them in the diet during specific life stages or disease states. Here, we discuss the classification of amino acids, methods to assess the needs for dispensable amino acids with experimental evidence from our recent studies, and highlight the role of specific dispensable amino acids in metabolism and health. Recent findings There exist differences among the dispensable amino acids to act as effective nitrogen sources in humans. Glycine, a dispensable amino acid is conditionally indispensable in later stages of human pregnancy. Summary The so-called ‘dispensable’ amino acids are quantitatively nearly 75% of the daily protein needs in humans. In certain life-stages and diseases, there is a dietary demand for the dispensable amino acids. Future well-designed studies are required to identify the dietary demand for these amino acids, which will certainly be useful for dietary management in specific diseases and to maintain health across all life-stages.

Extending the Range of SLIM-Labeling Applications: From Human Cell Lines in Culture to Caenorhabditis elegans Whole-Organism Labeling

“…Human cells require several E-AAs for growth. The definition of essential and dispensable amino acids is an ongoing subject of debate 11 and Reeds 12 stated “From a strictly metabolic perspective, there are only three indispensable amino acids (lysine, threonine, and tryptophan) and two dispensable amino acids (glutamate and serine)”. However, there is a generally accepted broader view of the essential nature of amino acids, in particular when in the context of cell lines in culture.…”

Determining amino acid requirements in humans

“…All determined amino acid requirements (lysine, TSAA, TAA and phenylalanine) increase by late stages of pregnancy ( 48 , 49 , 51 ), albeit at different amounts. Most interestingly, glycine a conditionally indispensable amino acid was shown to be indispensable in human pregnancy by late stages of pregnancy ( 50 , 53 ). It is of importance to note that in the glycine in pregnancy study, the amount of protein was fed at current pregnancy protein needs (0.88 g/kg/d), which further validates the finding that current protein intake recommendations in pregnancy are underestimates.…”

Tolerable Upper Intake Level for Individual Amino Acids in Humans: A Narrative Review of Recent Clinical Studies

“…Phenylalanine, an essential amino acid, is necessary for neurotransmitter synthesis via tyrosine [ 53 ]. Serine, a nonessential amino acid, is key for synthesizing other compounds, such as sphingolipids and amino acids, including glycine [ 54 ]. Miura et al.…”