Role of choline in human nutrition

Introduction

Choline is an essential nutrient to human body. It plays an important role in various physiological processes crucial for human health, as every cell in our body uses it. Despite the importance of choline, it's role is generally understated in the mainstream nutrition discussion. [1]

This review includes the scientific facts, physiological functions, dietary sources, and metabolic pathways of choline. We also go through the health problems caused by an inadequate intake.

Choline was first recognized as a dietary requirement in 1998 by the Institute of Medicine [2]. Since 1998, Choline has gained a lot of attention for its important role in human health. It is a constituent of phospholipids, neurotransmitters, and methyl donors, influencing cell structure, neurotransmission, lipid metabolism, and epigenetic regulation. Choline is often grouped together with other B vitamins.

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. Choline is crucial to lipid metabolism, and helping in fat transport. Choline has an important role on potentially reversing non-alcoholic fatty liver and preventing hepatic steatosis.

Dietary Sources and Metabolic Pathways

Dietary choline derives primarily from animal products such as eggs, liver, fish, and poultry. Choline is also found int plant-based sources, but with much less amounts. These plant-based sources include cruciferous vegetables and legumes [5]. When digested, 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

FDA has set the daily value (DV) for choline to 550 mg per day [4]. This applies both to adults and children (4 years and older). The 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 can be supplemented with various kinds of nutritional supplement products. These nutritional supplements often contain only choline, but they can also contain B-complex vitamins, or 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. Pregnant women are especially vulnerable to choline deficiency due to increased fetal demands for neural development.

There are some genetic variants that affect choline metabolism, which can further the choline deficiency in those individuals. One commonly mentioned genetic variant is MTHFR.