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.

Folate intake at RDA levels is inadequate for Mexican American men with the methylenetetrahydrofolate reductase 677TT genotype.

Since the establishment of the 1998 folate recommended dietary allowance (RDA), the methylenetetrahydrofolate reductase (MTHFR) 677C-->T variant has emerged as a strong modifier of folate status. This controlled feeding study investigated the adequacy of the RDA, 400 microg/d as dietary folate equivalents (DFE), for Mexican American men with the MTHFR 677CC or TT genotype. Because of the interdependency between folate and choline, the influence of choline intake on folate status was also assessed. Mexican American men (n = 60; 18-55 y) with the MTHFR 677CC (n = 31) or TT (n = 29) genotype consumed 438 microg DFE/d and total choline intakes of 300, 550 (choline adequate intake), 1100, or 2200 mg/d for 12 wk. Folate status response was assessed via serum folate (SF), RBC folate, plasma total homocysteine (tHcy), and urinary folate. SF decreased (P < 0.001) 66% to 7.9 +/- 0.7 nmol/L (means +/- SEM) in men with the 677TT genotype and 62% to 11.3 +/- 0.9 nmol/L in the 677CC genotype. Plasma tHcy increased (P < 0.0001) 170% to 31 +/- 3 micromol/L in men with the 677TT genotype and 18% to 11.6 +/- 0.3 micromol/L in the 677CC genotype. At the end of the study, 34% (677TT) and 16% (677CC) had SF concentrations <6.8 nmol/L and 79% (677TT) and 7% (677CC) had tHcy concentrations >14 micromol/L. Choline intake did not influence the response of the measured variables. These data showed that the folate RDA is not adequate for men of Mexican descent, particularly for those with the MTHFR 677TT genotype, and demonstrated a lack of influence of choline intake on the folate status variables measured in this study.