Dietary choline intake and biomarkers of choline status across the life cycle

Choline, an essential dietary nutrient for humans, is involved in a broad range of critical physiological functions as a precursor for the synthesis of acetylcholine, phospholipids, and betaine. The current dietary recommendations for choline were set as Adequate Intakes (AIs), estimated based on limited data and expressed as total choline. However, dietary choline is present in different forms, which can be classified as water-soluble forms (free choline, phosphocholine, and glycerophosphocholine), and lipid-soluble forms (phosphatidylcholine and sphingomyelin). Despite its importance, there is still limited information available about choline intake and plasma and milk concentrations. Therefore, the overall goal of my research was to advance our knowledge of choline nutrition. To address this goal, I conducted four studies on healthy participants of different age groups across the life cycle, in which dietary choline intake was assessed and/or milk and plasma concentrations of choline and metabolites were determined by stable isotope dilution liquid chromatography-tandem mass spectrometry. The first study validated a food frequency questionnaire to assess dietary total choline intake. The second study showed that the concentrations of water-soluble forms of choline in human milk samples did not differ between lactating women from a high- (Canada) and a low-income (Cambodia) countries; in both cases, the estimated means of milk total choline were below the AI for infants aged 0 – 6 mo. The third study showed that one fasted or fed blood sample was adequate to quantify plasma choline concentrations, but recent food intake increased its concentrations in healthy adults. The last study showed that plasma free choline was not associated with choline intake among toddlers, children, and adults. This research has generated a considerable body of information about choline nutrition across the life cycle. In conclusion, these results suggest an overestimation of the current choline AI for infants and possibly for lactating women, thus emphasizing a need for reevaluating the AIs. The absence of an association between dietary choline intake and plasma free choline suggests the need for a better understanding of choline nutrition and metabolism is warranted.Land and Food Systems, Faculty ofGraduat