FIGURE 2.

Influence of dietary choline intake on plasma choline metabolite concentrations. Pregnant women at <18 wk gestation were randomly assigned to receive either a choline supplement (750 mg choline/d) or a placebo (corn oil) from 18 wk pregnancy to 45 d postpartum. Choline and choline metabolite concentrations were measured by using liquid chromatography/mass spectrometry in plasma samples collected at 45 d postpartum. Values are plotted against total choline intake (diet plus supplement or placebo). Plots are shown for all metabolites measured in plasma. Regression models with metabolite as the response and total choline intake (diet plus supplement) as the predictor were fitted considering placebo subjects, supplemented subjects, or all subjects combined (3 solid lines). The following numbers of outliers (defined in Subjects and Methods) for each metabolite were excluded: subjects who received placebo only—choline (3), betaine (2), phosphatidylcholine (7), and sphingomyelin (4); subjects who received the supplement only—choline (2), betaine (4), phosphatidylcholine (4), and sphingomyelin (4); and all subjects combined—choline (3), betaine (7), phosphatidylcholine (7), and sphingomyelin (7). Weighted least-squares regression was performed in the model with plasma phosphatidylcholine to overcome heteroskedasticity. To achieve normality, log transformations were done on plasma betaine, choline, and phosphatidylcholine concentrations. Three statistical analyses were performed for each metabolite: the effect of intake on concentrations for the placebo group (indicated above the line on the left), the effect of intake plus the supplement on concentrations for the supplemented group (indicated above the line on the right), and the effect of intake plus the supplement on concentrations for the combined groups (indicated above the bracket). P values are indicated when differences were significant; group sizes for placebo and supplement groups were 46 and 48 subjects, respectively. The R² values for placebo, supplement, and placebo plus supplement groups, respectively, are as follows: for choline—0.11, 0.15, and 0.55; for phosphatidylcholine—0.004, 0.01, and 0.0001; for betaine—0.09, 0.07, and 0.56; and for sphingomyelin—0.07, 0.02, and 0.02. +, subjects randomly assigned to the placebo group; •, subjects randomly assigned to the choline supplement group.