Published online by Cambridge University Press: 10 December 2009
The term “conditionally essential” has been used to describe the role of choline, inositol, taurine, arginine, glutamine, and nucleotides in human nutrition. The biochemical pathways to synthesize these nutrients are present, and their absence from the diet does not lead to a classical clinical deficiency syndrome. However, under certain conditions, the biosynthetic capacity may be below functional metabolic demands. The conditions under which these nutrients may become essential include prematurity, certain disease states, periods of limited nutrient intake or rapid growth, and the presence of regulatory or developmental factors that interfere with full expression of the endogenous synthetic capacity. Under these conditions, dietary intake of the nutrient may optimize tissue function.
Several of the conditionally essential nutrients are present in significantly higher quantities in human milk versus infant formulas, and several are added to term and/or preterm formulas. On-going research will help to clarify their roles in neonatal nutrition and metabolism.
Choline was classified in 1998 as an essential nutrient for humans by the Food and Nutrition Board of the Institute of Medicine of the National Academy of Sciences. The Board recognized that fetal development and infancy constitute periods of increased demand for choline. The classification of choline as an essential nutrient will likely stimulate renewed interest and research in its role in the developing infant.
Choline has a variety of biological functions. It is a precursor for the neurotransmitter acetylcholine, and for two signaling lipids, platelet-activating factor and sphingosylphosphorylcholine.