Role of choline in human nutrition

Introduction

Choline, an essential nutrient often grouped with B vitamins, plays a pivotal role in various physiological processes crucial for human health [1]. Despite its significance, choline's role remains understated in mainstream nutrition discourse. This review aims to elucidate the scientific understanding of choline, its physiological functions, dietary sources, metabolic pathways, and the implications of inadequate intake on health outcomes.

Choline, first recognized as a dietary requirement in 1998 by the Institute of Medicine [2], has since garnered attention for its diverse roles in human health. It is a constituent of phospholipids, neurotransmitters, and methyl donors, influencing cell structure, neurotransmission, lipid metabolism, and epigenetic regulation.

Physiological Functions

Choline's primary function lies in cell membrane integrity [3], where it contributes to the synthesis of phosphatidylcholine, a major phospholipid. This role extends to neurotransmitter synthesis, particularly acetylcholine, impacting cognitive function, memory, and muscle control. Furthermore, choline is integral to lipid metabolism, aiding in fat transport and liver health by preventing hepatic steatosis.

Dietary Sources and Metabolic Pathways

Dietary choline derives primarily from animal products such as eggs, liver, fish, and poultry, with lesser amounts found in plant-based sources like cruciferous vegetables and legumes [5]. Upon ingestion, choline undergoes phosphorylation to phosphocholine, then sequential methylation to form betaine or conversion to acetylcholine via the Kennedy pathway. Excess choline can be oxidized to betaine, contributing to homocysteine metabolism.

Eggs are one of the best dietary sources of choline. One egg can contain about 147 mg of choline, which is about 27% of the daily value for choline [8].

In the United States, about half the dietary choline consumed is in the form of phosphatidylcholine [6,7].

Recommended Daily Value

In the United States, FDA set the daily value (DV) for choline to 550 mg per day [4]. This applies both to adults and children (4 years and older). This daily value was based on the population-coverage adequate intake for choline [4].

Adequate Intake for choline is different from daily value [4]. For people 19 years and older, the daily adequate intake is 550 mg for men 19, and 425 mg for women. For pregnant women adequate intake is 425mg, but for lactating women it is 550mg.

Nutritional supplements

Choline is available in different kinds of nutritional supplements. Some nutritional supplements contain only choline, some contain choline in combination with B-complex vitamins, and in some choline is paired with multivitamin/mineral products [9].

Typical amounts of choline in nutritional supplements range from 10 mg to 250 mg.

The forms of choline in dietary supplements include choline bitartrate, phosphatidylcholine, and lecithin.

Health Implications of Inadequate Intake

Choline deficiency manifests as impaired liver function, muscle damage, and cognitive deficits, underscoring its essentiality. Vulnerable populations include pregnant women due to increased fetal demands for neural development. Genetic variants affecting choline metabolism further accentuate individual susceptibility to deficiency-related disorders.

Conclusion

In conclusion, choline emerges as a critical yet undervalued nutrient in human nutrition, with far-reaching implications for health and well-being. Understanding its diverse roles, metabolic pathways, dietary sources, and associated health outcomes is imperative for promoting adequate intake and mitigating deficiency-related risks. Further research into choline's nuanced functions and optimal dietary strategies is warranted to optimize human health across the lifespan.