Global folate status in women of reproductive age: a systematic review with emphasis on methodological issues.

Inadequate folate status in women of reproductive age (WRA) can lead to adverse health consequences of public health significance, such as megaloblastic anemia (folate deficiency) and an increased risk of neural tube defect (NTD)-affected pregnancies (folate insufficiency). Our review aims to evaluate current data on folate status of WRA. We queried eight databases and the World Health Organization Micronutrients Database, identifying 45 relevant surveys conducted between 2000 and 2014 in 39 countries. Several types of folate assays were used in the analysis of blood folate, and many surveys used folate cutoffs not matched to the assay. To allow better comparisons across surveys, we attempted to account for these differences. The prevalence of folate deficiency was >20% in many countries with lower income economies but was typically <5% in countries with higher income economies. Only 11 surveys reported the prevalence of folate insufficiency, which was >40% in most countries. Overall, folate status data for WRA globally are limited and must be carefully interpreted due to methodological issues. Future surveys would benefit from using the microbiologic assay to assess folate status, along with assay-matched cutoffs to improve monitoring and evaluation of folic acid interventions, thus informing global efforts to prevent NTDs.

Development and Utility of a Birth Defects Surveillance Toolkit.

According to the World Health Organization (WHO), an estimated 303,000 neonates die within their first month of age every year globally as a result of a birth defect. Neural tube defects, serious birth defects of the brain and spine, are among the most common and severe of these birth defects. Since some low- and middle-income countries lack comprehensive, accurate data documenting the burden of these defects, providing technical assistance to help build birth defects surveillance programs can accelerate the collection of data needed to demonstrate this burden and advance prevention initiatives. We developed a birth defects surveillance toolkit, a technical assistance tool for country staff to help them implement birth defects surveillance. An evaluation of the toolkit with partners in Africa was conducted to assess perceptions of the usefulness, effectiveness, and policy impact of the surveillance toolkit and surveillance-related technical assistance provided to countries thus far. Overall, respondents provided very positive feedback about the toolkit components. Recommendations for improvement included customization to country contexts, such as photos reflective of African babies; surveillance examples from other countries; and consistent use of terms.

Adding folic acid to corn Masa flour: Partnering to improve pregnancy outcomes and reduce health disparities.

Although strides have been made in preventing neural tube defects (NTDs), Hispanic women remain more likely to have a baby born with an NTD and less likely to know the benefits of, or consume, folic acid than women of other race/ethnic groups. In 1998, the U.S. Food and Drug Administration (FDA) mandated that all enriched cereal grain products be fortified with folic acid; however, corn masa flour (CMF), used to make many corn products that are a diet staple of many Hispanic groups, was not included under this regulation. In 2006, a Working Group began a collaboration to address this disparity by pursuing a petition to FDA to allow folic acid to be added voluntarily to CMF. The petition process was a monumental effort that required collaboration and commitment by partners representing the affected population, manufacturers, scientists, and others. The petition was approved in 2016 and folic acid is now added to CMF products, with expected results of more women achieving the recommended daily folic acid intake, more infants born per year without an NTD, and millions of dollars in direct medical expenditures averted. This 10-year public-private partnership brought together diverse groups that traditionally have different goals. The Working Group continues to work toward ensuring that fortified CMF products are available to the consumer, with the end goal of achieving a reduction in NTD-affected pregnancies.

Optimal serum and red blood cell folate concentrations in women of reproductive age for prevention of neural tube defects: World Health Organization guidelines.

Neural tube defects (NTDs) such as spina bifida, anencephaly, and encephalocele are serious birth defects of the brain and spine that occur during the first month of pregnancy when the neural tube fails to close completely. Randomized controlled trials and observational studies have shown that adequate daily consumption of folic acid before and during early pregnancy considerably reduces the risk for NTDs. The U.S. Public Health Service recommends that women capable of becoming pregnant consume 400 µg of folic acid daily for NTD prevention. Furthermore, fortification of staple foods (e.g., wheat flour) with folic acid has decreased folate-sensitive NTD prevalence in multiple settings and is a highly cost-effective intervention.

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

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.

Assessing the association between the methylenetetrahydrofolate reductase (MTHFR) 677C>T polymorphism and blood folate concentrations: a systematic review and meta-analysis of trials and observational studies.

BACKGROUND: The methylenetetrahydrofolate reductase (MTHFR) 677C>T polymorphism is a risk factor for neural tube defects. The T allele produces an enzyme with reduced folate-processing capacity, which has been associated with lower blood folate concentrations. OBJECTIVE: We assessed the association between MTHFR C677T genotypes and blood folate concentrations among healthy women aged 12-49 y. DESIGN: We conducted a systematic review of the literature published from January 1992 to March 2014 to identify trials and observational studies that reported serum, plasma, or red blood cell (RBC) folate concentrations and MTHFR C677T genotype. We conducted a meta-analysis for estimates of percentage differences in blood folate concentrations between genotypes. RESULTS: Forty studies met the inclusion criteria. Of the 6 studies that used the microbiologic assay (MA) to measure serum or plasma (S/P) and RBC folate concentrations, the percentage difference between genotypes showed a clear pattern of CC > CT > TT. The percentage difference was greatest for CC > TT [S/P: 13%; 95% credible interval (CrI): 7%, 18%; RBC: 16%; 95% CrI: 12%, 20%] followed by CC > CT (S/P: 7%; 95% CrI: 1%, 12%; RBC: 8%; 95% CrI: 4%, 12%) and CT > TT (S/P: 6%; 95% CrI: 1%, 11%; RBC: 9%; 95% CrI: 5%, 13%). S/P folate concentrations measured by using protein-binding assays (PBAs) also showed this pattern but to a greater extent (e.g., CC > TT: 20%; 95% CrI: 17%, 22%). In contrast, RBC folate concentrations measured by using PBAs did not show the same pattern and are presented in the Supplemental Material only. CONCLUSIONS: Meta-analysis results (limited to the MA, the recommended population assessment method) indicated a consistent percentage difference in S/P and RBC folate concentrations across MTHFR C677T genotypes. Lower blood folate concentrations associated with this polymorphism could have implications for a population-level risk of neural tube defects.

Prenatal folic acid and risk of asthma in children: a systematic review and meta-analysis.

BACKGROUND: Childhood asthma has become a critical public health problem because of its high morbidity and increasing prevalence. The impact of nutrition and other exposures during pregnancy on long-term health and development of children has been of increasing interest. OBJECTIVE: We performed a systematic review and meta-analysis of the association of folate and folic acid intake during pregnancy and risk of asthma and other allergic outcomes in children. DESIGN: We performed a systematic search of 8 electronic databases for articles that examined the association between prenatal folate or folic acid exposure and risk of asthma and other allergic outcomes (eg, allergy, eczema, and atopic dermatitis) in childhood. We performed a meta-analysis by using a random-effects model to derive a summary risk estimate of studies with similar exposure timing, exposure assessment, and outcomes. RESULTS: Our meta-analysis provided no evidence of an association between maternal folic acid supplement use (compared with no use) in the prepregnancy period through the first trimester and asthma in childhood (summary risk estimate: 1.01; 95% CI: 0.78, 1.30). Because of substantial heterogeneity in exposures and outcomes, it was not possible to generate summary measures for other folate indicators (eg, blood folate concentrations) and asthma or allergy-related outcomes; however, the preponderance of primary risk estimates was not elevated. CONCLUSIONS: Our findings do not support an association between periconceptional folic acid supplementation and increased risk of asthma in children. However, because of the limited number and types of studies in the literature, additional research is needed.