Marisol Warthon-Medina

Zinc intake, status and indices of cognitive function in adults and children: a systematic review and meta-analysis

In developing countries, deficiencies of micronutrients are thought to have a major impact on child development; however, a consensus on the specific relationship between dietary zinc intake and cognitive function remains elusive. The aim of this systematic review was to examine the relationship between zinc intake, status and indices of cognitive function in children and adults. A systematic literature search was conducted using EMBASE, MEDLINE and Cochrane Library databases from inception to March 2014. Included studies were those that supplied zinc as supplements or measured dietary zinc intake. A meta-analysis of the extracted data was performed where sufficient data were available. Of all of the potentially relevant papers, 18 studies met the inclusion criteria, 12 of which were randomised controlled trials (RCTs; 11 in children and 1 in adults) and 6 were observational studies (2 in children and 4 in adults). Nine of the 18 studies reported a positive association between zinc intake or status with one or more measure of cognitive function. Meta-analysis of data from the adult’s studies was not possible because of limited number of studies. A meta-analysis of data from the six RCTs conducted in children revealed that there was no significant overall effect of zinc intake on any indices of cognitive function: intelligence, standard mean difference of <0.001 (95% confidence interval (CI) –0.12, 0.13) P=0.95; executive function, standard mean difference of 0.08 (95% CI, –0.06, 022) P=0.26; and motor skills standard mean difference of 0.11 (95% CI –0.17, 0.39) P=0.43. Heterogeneity in the study designs was a major limitation, hence only a small number (n=6) of studies could be included in the meta-analyses. Meta-analysis failed to show a significant effect of zinc supplementation on cognitive functioning in children though, taken as a whole, there were some small indicators of improvement on aspects of executive function and motor development following supplementation but high-quality RCTs are necessary to investigate this further.

DIET@NET: Best Practice Guidelines for dietary assessment in health research

BackgroundDietary assessment is complex, and strategies to select the most appropriate dietary assessment tool (DAT) in epidemiological research are needed. The DIETary Assessment Tool NETwork (DIET@NET) aimed to establish expert consensus on Best Practice Guidelines (BPGs) for dietary assessment using self-report.MethodsThe BPGs were developed using the Delphi technique. Two Delphi rounds were conducted. A total of 131 experts were invited, and of these 65 accepted, with 48 completing Delphi round I and 51 completing Delphi round II. In all, a total of 57 experts from North America, Europe, Asia and Australia commented on the 47 suggested guidelines.ResultsForty-three guidelines were generated, grouped into the following four stages: Stage I. Define what is to be measured in terms of dietary intake (what? who? and when?); Stage II. Investigate different types of DATs; Stage III. Evaluate existing tools to select the most appropriate DAT by evaluating published validation studies; Stage IV. Think through the implementation of the chosen DAT and consider sources of potential biases.ConclusionsThe Delphi technique consolidated expert views on best practice in assessing dietary intake. The BPGs provide a valuable guide for health researchers to choose the most appropriate dietary assessment method for their studies. These guidelines will be accessible through the Nutritools website, www.nutritools.org.

The Long Term Impact of Micronutrient Supplementation during Infancy on Cognition and Executive Function Performance in Pre-School Children

Brain growth and development are critically dependent on several micronutrients. During early development cellular activity may be sensitive to micronutrient deficiencies, however the evidence from human studies is equivocal. The objective of this study was to examine the long-term cognitive and social-emotional effects of multiple micronutrient supplementation compared with iron supplementation alone, administered during infancy. This study was a follow-up to an initial randomized, double-blind controlled trial (RCT) in 2010 in which 902 infants, aged 6–17 months, from Lima, Peru, were given daily supplements of either iron (Fe) or multiple micronutrients (MMN) including zinc (451 in each group). The supplementation period for both groups was six months. In 2012, a subsample of 184 children from the original cohort (now aged 36–48 months) was randomly selected to participate in a follow-up trial and was assessed for intelligence, working memory, inhibition, and executive function. The tests showed no significant differences between the supplementation groups though there were some gender differences, with girls displaying higher scores than boys across both groups on the Wechsler Preschool and Primary Scale of Intelligence (WPPSI) Verbal IQ sentences subtest, the Day-Night cognitive test and on the Brief Infant-Toddler Social Emotional Assessment (BITSEA) social competency, and boys scoring higher than girls in problem behaviour. The results indicate that MMN supplementation had no long term additional effects on cognitive function compared with iron supplementation alone. The timing of supplement administration for maximum impact on a child’s cognitive development requires further investigation.

Dietary zinc intake and whole blood zinc concentration in subjects with type 2 diabetes versus healthy subjects: A systematic review, meta-analysis and meta-regression

The aim of this systematic review, meta-analysis and meta-regression was to examine the relationship between type 2 diabetes mellitus (T2DM) and concentration of zinc in whole blood, as well as dietary zinc intake. Searches were performed using Ovid MEDLINE, Embase (Ovid) and The Cochrane Library (CENTRAL). Observational studies conducted on diabetic and healthy adults, with data on dietary zinc intake and/or concentration of zinc in whole blood, were selected. The search strategy yielded 11,150 publications and the manual search 6, of which 11 were included in the meta-analyses. Mean difference (MD) and 95% confidence interval (CI), were calculated using the generic inverse-variance method with random-effects models. Heterogeneity was assessed by the Cochran Q-statistic and quantified by the I2 statistic. Meta-regressions and stratified analysis were used to examine whether any covariate had influence on the results. The pooled MD for the dietary zinc intake meta-analysis was -0.40 (95% CI: -1.59 to 0.79; I2u202f=u202f61.0%). Differences between diabetic and non-diabetic subjects became significant in the presence of complications associated with diabetes (MDu202f=u202f-2.26; 95% CI: -3.49 to -1.02; I2u202f=u202f11.9%). Meta-regression showed that for each year since the diagnosis of diabetes the concentration of zinc in whole blood decreased in diabetic patients regarding healthy controls [MD (concentration of zinc in blood)u202f=u202f732.61u202f+u202f(-77.88303)u202f×u202f(duration of diabetes in years)], which is not generally explained by a lower intake of zinc.

Development of Nutritools, an interactive dietary assessment tools website, for use in health research

Abstract Background Measuring dietary intake is difficult, and strategies that enable researchers to select the most appropriate dietary assessment tools are needed. The aim of this work was to improve the quality of dietary data collected in epidemiological studies. Therefore, the DIETary Assessment Tools NETwork (DIET@NET) partnership, a network of scientific experts, has created the Nutritools website. Methods Development of the Nutritools website was divided into three strands: creation of best practice guidelines, developed with the Delphi technique to obtain expert views (the guidelines enable researchers to choose the most appropriate dietary assessment tool for their work); creation of an interactive dietary assessment tool e-library, with eligible dietary assessment tools being identified through a systematic review of reviews that searched seven databases; and creation of an online interface between food tables and dietary assessment tools—namely, the Food Questionnaire Creator (FQC). The work was guided by the DIET@NET partnership. Findings Interactive dietary assessment guidelines were generated with feedback from 57 international experts. 43 guidelines and a summary of the strengths and weaknesses of the dietary assessment methods were included. The dietary assessment tool e-library included data for 62 UK validated tools, which were obtained from 43 systematic reviews identified. The tool library will provide in-depth information about the tools, validation study characteristics, and results. This information is also provided visually through bubble and summary plots, allowing easier comparison between the dietary assessment tools. The FQC was based on the principles of common food frequency questionnaires and allows users to create and develop new online food questionnaires. Users can map their online questionnaires to the latest UK food database (McCance and Widdowsons Composition of Foods, 7th edn). The FQC will also host a number of validated dietary assessment tools that have been adapted for online use. Interpretation The DIET@NET partnership has created a unique dietary assessment reference website (live from November, 2017) using expert guidance and systematic review. The website allows visual comparison of dietary assessment tools and hosts validated, interactive tools. The best practice guidelines assist researchers in selecting the most appropriate tool for their study. Researchers can access validated dietary assessment tools through the e-library and create their own using the FQC. Funding UK Medical Research Council (grant no MR/L02019X/1).

A new approach for developing food frequency questionnaires: the Food Questionnaire Creator

The number of validated dietary assessment tools that are easily accessible to researchers are limited. Therefore, the DIETary Assessment Tools NETwork (DIET@NET) project aims to develop a central resource that will provide access to validated dietary assessment tools, and provides a structured system that will enable the creation of online questionnaires. The development of this online platform was overseen by the DIET@NET partnership that appraised commonly used questionnaires to collect dietary data. The selection of questionnaires was part of a systematic review of systematic reviews which identified validated dietary assessment tools. The result of this evaluation was the creation of an online platform called the ‘Food Questionnaire Creator (FQC)’, which will be accessible on the Nutritools website, www.nutritools.org, a central resource for researchers undertaking studies which require dietary measurement. The FQC hosts a number of existing validated food questionnaires which have been transformed and updated from paper-based to web-based. The FQC will also enable researchers to generate new online questionnaires or adapt existing tools; set up a project and send the questionnaire to participants for completion either on-line or paper based; provide detailed nutrient outputs. To use the FQC the relevant foods or combinations of foods must be added; frequency of consumption and information on food portions. Foods will be mapped to the latest UK food composition database. We aim to link the FQC with the National Diet and Nutrition Survey to generate recommended foods contributing to a particular nutrient of interest to include in a questionnaire. All newly developed FQC questionnaires can be made public. Although, currently the FQC only provides UK dietary assessment tools and databases, it has been developed to allow for international databases and tools to be added. The FQC provides researchers with a range of validated paper-based dietary assessment tools online. The FQC enables researchers to generate reliable food questionnaires. We encourage researchers to make their dietary assessment tools more accessible to others, leading to better consistency and comparability of research in nutrition. This project was funded by the Medical Research Council (MRC) (ref: MR/L02019X/1).

Zinc intake and plasma/serum zinc concentration: a systematic review and meta-analysis of randomized controlled trials

A systematic review of randomized controlled trials (RCTs) was conducted to investigate how Zn intake influences plasma/serum Zn concentrations. We used protocols developed by EURRECA to perform a literature search for papers published up until February 2010 through MEDLINE, EMBASE, and Cochrane Library CENTRAL. We extracted data from studies that investigated apparently healthy adults and elderly, and conducted the metaanalysis using STATA (11.0). The relationship between Zn intake and plasma/serum Zn concentrations following intervention was expressed as a regression coefficient (beta), i.e., the gradient of the response curve expressed on a natural log scale. The final metaanalysis included 31 data sets from 15 RCTs. Pooled data revealed a significant relationship between Zn intake and plasma/serum Zn concentrations with an overall beta value of 0.14 (95% CI 0.11-0.18, P