Dietary monoglutamate and polyglutamate folate are associated with plasma folate concentrations in Dutch men and women aged 20-65 years

Dietary folate consists of monoglutamate and polyglutamate folate species. In the small intestine, folate polyglutamate is deconjugated to the monoglutamate form before absorption takes place. This enzymatic deconjugation might limit the bioavailability of polyglutamate folate. Until now, no data have been available on dietary intake of both folate forms and their associations with folate status. Therefore, we estimated the intake of monoglutamate and polyglutamate folate in the Dutch population and studied whether the association with plasma folate is different for these two folate forms. Dietary intake of monoglutamate and polyglutamate folate from nonfortified foods was estimated for 2435 subjects (1275 men; 1160 women) aged 20–65 y. The intake of monoglutamate folate was about one third of total folate intake, derived mainly from bread (20%) and meat (18%), whereas two thirds consisted of polyglutamates, derived mainly from vegetables (25%). The predictive power of the regression model with total folate intake as the independent variable adjusted for age, smoking and alcohol intake, did not increase when including the ratio of monoglutamate to polyglutamate folate intake. In addition, linear regression models showed that both monoglutamate and polyglutamate folate intake were associated positively with plasma folate levels. However, in men, the monoglutamate folate form appeared to be a threefold stronger determinant of plasma folate levels than polyglutamate folate, whereas in women, both folate forms were equally strong determinants. This might be explained by different food intake patterns of men and women, including alcohol intake. At present, it does not seem necessary to distinguish between food folate forms in advising an increase in folate intake from nonfortified foods

Effect of the methylenetetrahydrofolate reductase 677C-->T mutation on the relations among folate intake and plasma folate and homocysteine concentrations in a general population sample.

Item does not contain fulltextBACKGROUND: Methylenetetrahydrofolate reductase (MTHFR) is a key enzyme in folate and homocysteine metabolism. The common MTHFR 677C-->T polymorphism decreases the enzyme's activity. OBJECTIVE: The objective of the study was to assess the effect of the polymorphism on the relations among folate intake, plasma folate concentration, and total plasma homocysteine (tHcy) concentration. DESIGN: The design was a cross-sectional analysis in a random sample (n = 2051) of a Dutch cohort (aged 20-65 y). RESULTS: At a low folate intake (166 micro g/d), folate concentrations differed significantly among the genotypes (7.1, 6.2, and 5.4 nmol/L for the CC, CT, and TT genotypes, respectively; P for all comparisons 0.2; <13.1 for all genotypes). The relation between folate intake and tHcy concentration had a pattern similar to that of the relation between plasma folate and tHcy concentrations. CONCLUSIONS: At any folate intake level, TT subjects have lower plasma folate concentrations than do CT and CC subjects. Yet, at high plasma folate concentrations, tHcy concentrations in TT subjects are as low as those in CT and CC subjects

Serum vitamin B-12 concentrations within reference values do not exclude functional vitamin B-12 deficiency in PKU patients of various ages

Homocysteine (Hcy) and in particular methylmalonic acid (MMA) are considered reliable parameters for vitamin B-12 status in healthy individuals. Phenylketonuria (PKU) patients are at risk for functional vitamin B-12 deficiency based on their diet. Objective: The aim of this study was to investigate the prevalence of functional vitamin B-12 deficiency in continuously treated PKU patients and the association of parameters of vitamin B-12 and metabolic control. Methods: In 75 continuously treated PKU patients of 1-37 years of age, serum vitamin B-12 concentrations, plasma Hcy, MMA, and phenylalanine concentrations were studied. Results: Eight patients had vitamin B-12 concentrations below normal. Out of these eight patients, two had elevated MMA and/or Hcy concentrations. Ten other patients with normal vitamin B-12 concentrations had elevated concentrations of MMA and/or Hcy. Conclusions: A vitamin B-12 concentration within the reference range does not automatically imply a sufficient vitamin B-12 status. We recommend measuring serum MMA. or alternatively plasma Hcy, yearly in all PKU patients to diagnose functional vitamin B-12 deficiency. (C) 2010 Elsevier Inc. All rights reserved