Measuring Zinc Intake Among Children in Luwelezi Mzimba

TITLE: Validating the Zinc intake amongst Children aged 24-36 months in Luwelezi Mzimba using food frequency questionnaire.

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Our bodies contain 1.5 to 2.5 grams of zinc, found in all organs, tissues, and body fluids .Zinc is essential for the growth and repair of tissues because it is involved in the synthesis of DNA and RNA, therefore making Zinc Very important for the Developing child (24-36 months). Zinc intake correlates directly with protein consumption, groups are at risk because of limited meat intake. Zinc deficiency in children effects growth retardation, skeletal abnormalities, impaired immunity and Poor wound healing. Zinc deprivation impairs growth and development of infants and children. Evidenced with studies that showed zinc supplements produced highly significant improvements in linear growth and weight gain of children .Consequently Zinc intake estimate are important both for epidemiological studies and in the clinical setting. A reliable assessment of nutrient intake is a difficult task, and the choice of method depends on the aim of the study. Food frequency questionnaires (FFQs) is a practical tool for validating nutrient consumption, however can the same be noted when validating Zinc intakes.

OBJECTIVE: To assess the Validity of zinc intake using a food frequency questionnaire for children between 24-36 months.


A longitudinal survey design was conducted, data was collected twice over the year.Calculation of sample Size.

Total number = 96, using error of mean 10%, 50% CV and 95% confidence level.

Exclusion Criteria was used, this included the ability to keep a diet record therefore only Parents and Guardians that were literate, no previous involvement in a diet assessment study, and no major diet changes in the past 6 months. Leading to the study recruiting n=85 Children (age range 24 – 36 months) from Luwelezi in Mzimba. Participants were selected using Simple random sampling. Informed consent was obtained from participating parent/guardian, and a special effort was made by the Nutritionist to illuminate the importance of an accurate and not manipulated 3 day diet record. Collecting biological samples is often culturally unacceptable, moreover with children (aged 24 – 36 months) to rural populations in countries like Malawi and opportunistically getting samples from children already compromised at Hospitals/Clinics cannot offer the correct reflection of Zinc intake due to some already being Zinc deficient. According to a study by Gibson he found that Zinc level findings of dietary recall to biochemical indexes were significantly similar of 60 women in southern Malawi, therefore this study will not be using biochemical markers. Ethical approval was sorted from Local, District and National authorities.

Zinc FFQ

Although the FFQ is apt to self-administration, in this study it was administered by a trained interviewer, this was done due to low literacy rates and thus to improve accuracy. The operation required less than 10 min for each interview. Biasness arises when collecting data using FFQ done once a year, which may introduce a seasonal bias because certain foodstuffs are often consumed only at one time of the year. Therefore, this study collected data during both seasons rather than just at one time then calculated the average.

The steps that were taken to improved internal validity of the FFQ included, Assembled and calibrated equipment a selection of local utensils were purchased and calibrated with a standard measuring cup. Acquirement of Picture charts depicting the foods most often eaten in Mzimba. Translated and pretested the FFQ was translated into local Language Chichewa & Tumbuka, a pilot draft of the questionnaire was tested on a smaller sample, using respondents similar to actual population. Trained the interviewers adequate training for the interviewers is critical. The interviewing techniques should always be consistent both among the interviewers and over time.

Estimating portion sizes is the most challenging part of the recall interview but also one of the most critical for ensuring high-quality results. This study used clay molded into the correct size and shape of the food to help estimation. Converting portion sizes to weight equivalents ,portion sizes was converted into weight equivalents by using dietary scales and using leftover portions to Calculated the proportion of edible percentage. FFQ usually suffer from overestimations or underestimation, this will reduce them errors. Reviewed the recall interview data at the end of the interview with respondent being present.

Atomic Absorption Spectroscopy

Some nutrient composition values for a local staple food could not be derived, therefore the study obtained direct chemical analysis. This approach is especially desirable for zinc because their content in plant-based Staples often depends on local trace element levels in soil, agronomy practices. The principle of analysis is to determine zinc using flame atomic absorption spectrometry (AAS) based upon the absorption of radiation by free atoms .This was done by preparations of three replications of each concentration in order to get an average using 100-mL volumetric flasks. In order to determine the total amount of zinc, multiply the concentration obtained by the dilution factor (100mL).

3 day food record

After completing the FFQ, subjects were asked to keep a 3 day estimated diet diary (food record), recording everything they ate and drank, at the time of eating. A list of household measures was enclosed with the diary form. Comprehensive verbal and written instructions were given to the subjects on the methods of recording data. Emphasis was put during the explanatory phase prior to diet recording to just record the actual intake without any fear of judgment relative to nutrition.

Estimation of Zinc nutrient scores

For each food item, zinc nutrient content per average unit was compiled. Using Nutritional composition of each food derived from the US Department of Agriculture (USDA) food composition tables and Diet Master 2100 software when necessary was developed allowing the total Zinc intake for the FFQ and 3 Day Record to be calculated and compared to AAS.


Zinc intakes were calculated separately for FFQ, 3 day Record and AAS, and only then were comparisons made (refer to Fig 1). Calculating total zinc intakes Once the daily food intake has been measured, total zinc intakes can be calculated by multiplying the amount (g) of each food consumed by its zinc content (mg zinc/100 g). Specificity was defined as the proportion of those with a daily Zinc intake below 0.80mg on the FFQ. Sensibility was defined as the proportion of those with a daily Zinc intake above 0.8mg on the FFQ. Confidence intervals at 95% were also calculated using Excel 2013 software, ANOVA single Factor refer to Fig: 1.


The study had 85 respondents of which 47 (55.3%) were females and 38 (44.7%) were boys refer to graph 1. The average age of the Respondents was 29.0 ± 1.2 months. Mean dietary Zinc intake from the 3 Day diet records was 0.909 mg=day with a variance of 0.041, whilst FFQs was 0.90mg=day with a variance of 0.0366 and AAS was 0.89mg=day with a variance of 0.0366. The normal distribution of Zinc data from both diet AAS, 3 day record and FFQ revealed no significant difference between mean intakes (P?0.064).

















3 Day Food Record





Source of Variation






F crit

Between Groups







Within Groups







Fig 1: Anova Single Factor for zinc Intake for the children diets, with P-value of 0.91.Results shows they is a no significant difference in zinc intake between the 3 methods used.


The study findings showed that all the assessment tools used to assess zinc intake were equally precise as evidenced by Figure 1 (F= 0.09?3.03, p = 0.91), this shows that they is no significant difference in findings, the different assessment tools were able to come up with similar results in zinc intakes of all the n=85 respondents . Hence increasing the reliability of FFQ, since it is one of the most used instruments in the majority of large-sample studies in nutritional epidemiology. Validation studies are carried out to measure the extent to which a method actually measures the aspect of the diet it was designed to measure with the group being measured. Validity and reliability are currently used criteria for selecting dietary assessment tools for observational research. However it is important to note that validation procedure of a dietary assessment tool is essentially impossible, as there is no absolute gold standard for measuring dietary intake


The purpose of this study was to validate Zinc intake for children in Luwelezi Mzimba using the FFQ. It was found that they was a significant correlation of Zinc intakes between all the methods used to calculate zinc intake, therefore the study justifies that FFQ is a valid tool in assessing dietary intake of Zinc.


Using FFQ is depends solely upon the respondent’s memory.
Calculating procedures based on estimation and assumptions.



Systematic universal approach to determine nutrition status is an essential to achieve global health, recommended by the World Health Organization (WHO). This assessment allows explanation of present and past occurrences, hence indicates likelihoods of future possibilities to child’s health. For this purpose, growth charts are adopted, in April 2011 Malawi also joined the 125 Countries across the world shifting from National Center for Health Statistics (NCHS/1978) to WHO/ 2006.This paper aims to explore why it was necessary for Malawi to make this outstanding change.

The recommendation for adopting the WHO standards for Malawi are based on several considerations including:


The production of the WHO child growth curves underwent a careful, methodical process. Which included vicious methods of data collection, standardized across sites has to be followed during the entire study, thus exclusion criteria develop. Sound procedures for data management and cleaning were applied). The selection of the best statistical approaches and State-of-the-art statistical methodologies used to generate these standards making them the highest conceivable quality Smoothed curves and empirical methods indicating a true description of the growth of healthy children, in contrast the NCHS/WHO data was collected from 1929 to 1975 and does not even match current national birth weight distributions. Also, the statistical methods available at the time the NCHS/WHO growth curves were constructed were too limited to correctly model the pattern and variability of growth. As a result, the NCHS/WHO curves do not adequately represent early childhood growth. The equipment by NCHS in 1977 cannot be matched to State-of-the-art statistics used by WHO in 2004. Equally evidenced by differences between recumbent length measurements from the Fels data and the stature measurements from the NCHS data sets were larger than expected when the transition was made from recumbent length to stature between 24 and 36 months compared to WHO standard.


WHO and UNICEF have developed a network with facilitators which aim at supporting training and other technical aspects of the standards’ implementation at regional and country level. They provide training packages emphasizing the importance of accurate measurement, plotting and interpretation, plus documentation of growth problems. A child that has a nutritional growth problem, is identified and appropriate action should be determined to address it. Growth assessments by NCHS/WHO is not supported by appropriate response actions to prevent and treat excessive or inadequate growth, hence it is not effective in improving child health. Some Malawian settings where parents are not able to seek and afford treatment plus no presence of an NGO leaves the diagnosed child in grave danger. Another plus for WHO growth charts is that their study was followed incrementally, with each infant measured 21 times between birth and two years. The shorter measurement intervals results in a better tool for monitoring the rapid and changing rate of growth in early infancy However, the NCHS/WHO infants were measured once every 3 months and used supplemental data due unavailable data for the first two to three months of life. The cross-sectional nature of the NCSH/WHO charts represents achieved size of infants, it does not describe rates of growth as accurately as growth represented in longitudinal growth charts


The WHO growth standard promotes breastfeeding as the custom that should be followed to attain optimal growth among children exclusively or predominantly breastfed. This is consistent with the Malawi’s Baby-friendly Hospital approach. Infant feeding guidelines recommend breastfeeding as the peak source of nutrition during infancy. Thus, the WHO standards provides a platform for advocating the protection, promotion and support of breastfeeding and adequate complementary feeding. In this regard, the WHO standards are expected to make meaningful contributions to reducing child morbidity and mortality in Malawi. This will now allow accurate assessment, measurement and evaluation of breastfeeding and complementary feeding because it recognizes the adequacy of human milk to support healthy growth and development. However the NCHS/WHO nearly all infants included in the sample were formula-fed resulting in a reflection different to the pattern of growth typically observed in healthy breastfed infants. This makes it gravely suitable for Malawi due to most of our infants being Breastfed, therefore exposing them the many benefits exclusive breastfeeding come with promoting optimal child health.


Children in the WHO standards were raised under ideal circumstances and health conditions. As a result the WHO growth charts are designated as the Golden standard identifying how children should grow when provided with optimal conditions .On contrast with NCSH/WHO charts which shows a snapshot of weight and heights of the sampled population, irrespective of whether their rate of growth was optimal or not. Therefore the NCSH/WHO charts potentially show the growth of some infants who may have been fed sub-optimally, raised in substandard environmental circumstances; or had infections, chronic illness or disease. Adopting this “Golden Standard” is helpful for Malawi as it allows the comparison to be made with the very best.


The origins of the children included in the WHO standards were widely diverse. They included peoples from Europe, Asia, Africa, Latin America and the Middle East In this respect they are similar to a lot of populations ,due being ethnic diverse. The growth of the children in the 6 various sites was very similar because their environments were similarly healthy. This indicates that we should expect the same potential for growth in any country. Traditionally it was believed that different ethnic groups show different patterns of growth. However WHO standards has refuted this belief showing that variability in infant growth was greater within population groups than between the different country groups. The major Concern with NHCS charts is that the sample consisted primarily of white middle-class infants from southwestern Ohio (USA). So making the data obtained unrepresentative, WHO charts means Malawians are also capable of growing to these heights under optimal conditions. ‘Osati zungu simuthu, amakula kwambiri kuposa ife Amalawi’.


WHO Standard approach goes beyond the development of growth references towards a standard, inclusion of motor development milestones provide a solid instrument for helping to meet the health and nutritional needs of the world’s children. A further set of charts comprising: MAUCZ, HCZ, SSFZ and TSFZ were released early in 2007. All charts are available both percentiles and Z-scores, making it easier than ever before to record and assess Nutritional status of infants, one can just get a paper, pen and MAUC tape fold in the pocket and off they go into the Community. Then generate reports using WHO Anthro, which is an exciting software in itself.


After sensible and carefully evaluation the adoption of the WHO charts for usage in Malawi appears more helpful for the children’s nutritional screening and hence hospital admission than NCSH/WHO growth References. This is due it enables the detection of a higher number of malnourished children or at nutritional risk, thus allowing the much needed beneficial early intervention to be undertaken. Also the Development of WHO charts were promoted and supported by Stakeholders (NGO’s, Governments etc.) that are currently active in Malawi and contribute significantly to our National Budget, WHO charts makes it easier for steadfast interventions and communication between these stakeholders and Malawi .