Assessing the association between natural food folate intake and blood folate concentrations: a systematic review and Bayesian meta-analysis of trials and observational studies.

Claire Marchetta,Joseph Mulinare,Amy Cordero,Robert Berry,Jing Guo,Becky Tsang,Patricia Mersereau,Jorge Rosenthal,Heather Hamner,Krista Crider,Yan Qi,Owen Devine

doi:10.3390/nu7042663

Abstract

Folate is found naturally in foods or as synthetic folic acid in dietary supplements and fortified foods. Adequate periconceptional folic acid intake can prevent neural tube defects. Folate intake impacts blood folate concentration; however, the dose-response between natural food folate and blood folate concentrations has not been well described. We estimated this association among healthy females. A systematic literature review identified studies (1 1992–3 2014) with both natural food folate intake alone and blood folate concentration among females aged 12–49 years. Bayesian methods were used to estimate regression model parameters describing the association between natural food folate intake and subsequent blood folate concentration. Seven controlled trials and 29 observational studies met the inclusion criteria. For the six studies using microbiologic assay (MA) included in the meta-analysis, we estimate that a 6% (95% Credible Interval (CrI): 4%, 9%) increase in red blood cell (RBC) folate concentration and a 7% (95% CrI: 1%, 12%) increase in serum/plasma folate concentration can occur for every 10% increase in natural food folate intake. Using modeled results, we estimate that a natural food folate intake of ≥450 μg dietary folate equivalents (DFE)/day could achieve the lower bound of an RBC folate concentration (~1050 nmol/L) associated with the lowest risk of a neural tube defect. Natural food folate intake affects blood folate concentration and adequate intakes could help women achieve a RBC folate concentration associated with a risk of 6 neural tube defects/10,000 live births.

Highlights

Folate, the umbrella term used to describe both natural food folate and synthetic folic acid, is necessary for basic cellular functions
We found that natural food folate intake has an impact on both RBC folate and serum/plasma folate concentrations, the precision of the estimates differ
Using the derived model for data reported using microbiologic assay (MA), we estimate that a 10% increase in natural food folate intake could lead to an increase in RBC folate concentration of 6% (95% credible intervals (CrI): 4%, 9%)

Summary

Introduction

The umbrella term used to describe both natural food folate and synthetic folic acid, is necessary for basic cellular functions. Natural food folate can be found in liver, dark green leafy vegetables, legumes, and some fruits, such as oranges [1]. Natural food folate’s bioavailability is less than synthetic folic acid [1,2,3] in part because it must undergo deconjugation before it can be absorbed and made available for metabolic reactions and/or storage. Research has indicated that relative to the consumption of folic acid with food, the bioavailability of natural food folate is approximately 50% [2]. Equivalents (DFE) = 0.6 μg folic acid [2]. DFEs are a unit of measurement that reflect the greater bioavailability of folic acid compared to natural food folate [2]

Methods

Results

Discussion

Conclusion