Adequate Intake levels of choline are sufficient for preventing elevations in serum markers of liver dysfunction in Mexican American men but are not optimal for minimizing plasma total homocysteine increases after a methionine load.

BACKGROUND: An adequate intake of 550 mg choline/d was established for the prevention of liver dysfunction in men, as assessed by measuring serum alanine aminotransferase concentrations.
OBJECTIVE: This controlled feeding study investigated the influence of choline intakes ranging from 300 to 2200 mg/d on biomarkers of choline status. The effect of the methylenetetrahydrofolate reductase (MTHFR) C677T genotype on choline status was also examined.
DESIGN: Mexican American men (n = 60) with different MTHFR C677T genotypes (29 677TT, 31 677CC) consumed a diet providing 300 mg choline/d plus supplemental choline intakes of 0, 250, 800, or 1900 mg/d for total choline intakes of 300, 550, 1100, or 2200 mg/d, respectively, for 12 wk; 400 mug/d as dietary folate equivalents and 173 mg betaine/d were consumed throughout the study.
RESULTS: Choline intake affected the response of plasma free choline and betaine (time x choline, P < 0.001); the highest concentrations were observed in the 2200 mg/d group. Phosphatidylcholine (P = 0.026) and total cholesterol (P = 0.002) were also influenced by choline intake; diminished concentrations were observed in the 300 mg/d group. Phosphatidylcholine was modified by MTHFR genotype (P = 0.035; 677TT < 677CC). After a methionine load (100 mg/kg body wt), choline intakes of 1100 and 2200 mg/d attenuated (P = 0.016) the rise in plasma homocysteine, as did the MTHFR 677TT genotype (P < 0.001). Serum alanine aminotransferase was not influenced by the choline intakes administered in this study.
CONCLUSIONS: These data suggest that 550 mg choline/d is sufficient for preventing elevations in serum markers of liver dysfunction in this population under the conditions of this study; higher intakes may be needed to optimize other endpoints.