Undernutrition resulting from inadequate access to high-quality, nutritious food is a widespread issue in sub-Saharan Africa impacting the health and survival of mothers and their children. Inadequate dietary intake leads to a deficiency in nutrients including calcium, required for growth and physiological functioning. This study investigated the potential of increasing dietary calcium intake by the addition of heat-treated ground eggshell to locally prepared food. A mixed methods approach of literature review, Delphi expert survey and focus group discussions with women of childbearing age in rural Tanzania, were used to assess the practicality, safety, and acceptability of consumption of ground eggshell. Chicken eggshell has high calcium content (380 mg of calcium/gram) and bioavailability comparable to calcium carbonate (~39%) with 1 g sufficient to provide one half of a sub-Saharan African adult female’s dietary calcium needs. Salmonella was indicated as the most likely threat to human health through eggshell consumption. Experts agreed that eggshells boiled for 10 min when preparing hard-boiled eggs with a further 20 min cooking of crushed eggshell in staple foods would eliminate identified egg-associated pathogens. Five focus groups (n = 46) indicated eggshells were perceived as waste. However, there was an indication of general acceptance of the approach and a willingness to consider the incorporation of ground eggshells into their diets. Development of suitable communication methods are required to convey benefits and safe preparation methods. Ground eggshell could be a highly equitable method of increasing calcium intakes across rural sub-Saharan Africa where calcium intake is low and village poultry ownership common.
A literature review was conducted to determine the following: Three databases, PubMed, Web of Knowledge, and Medline, were searched in March 2016 for qualitative and quantitative research published between 1976 and 2016. Subject and keyword (multipurpose) search terms related to eggshell, food safety, and nutrition were combined using Boolean operators. Search terms were eggshell* AND chicken OR poultry AND *availability OR digestibility OR *nutrient* OR safety OR calcium OR limitations OR vitamin* OR sanit* OR foodborne OR health OR salmonella OR diet* OR dietary supplement OR composition AND human nutrition OR sub‐Saharan Africa OR Africa OR children OR adult* OR women OR food insecurity OR human* OR eating. Reference lists of relevant articles were hand searched for additional references. Citation searches were also conducted on relevant articles. The recommended daily allowance of calcium set by the WHO for women (including the maternal life stages of preconception, pregnancy and lactation) and children were compared against calcium content per mean gram of ground chicken eggshell from the literature review. A method of preparing ground eggshell and adding it to food was then proposed. A two‐round modified e‐Delphi survey containing both qualitative and quantitative questions was conducted to ascertain expert opinions on microbial food safety risks regarding human consumption of chicken eggshell (Appendix S1). The Delphi method is a structured communication process consisting of at least two rounds of questionnaires peppered with opinion feedback to evoke and refine group judgement of experts (Boulkedid, Abdoul, Loustau, Sibony, & Alberti, 2011; Rowe & Wright, 1999). Both rounds of the survey were pretested for ease of completion, readability, and clarity by independent reviewers from the University of Sydney. A panel of individuals from existing personal networks of researchers with expertise in egg‐associated pathogens was selected. Nineteen experts (16 experts from personal contacts and three from snowball sampling) were contacted; six participated in the initial round; five completed the second‐round survey. The five were internationally recognised experts from Australia, Belgium, Canada, Scotland, and USA with experience in resource‐limiting settings. Four were university professors, and one was an international research centre programme leader. Their self‐reported expertise was related to egg microbiology, egg production systems, poultry microbiology, poultry medicine, poultry health, and food safety. The survey assessed microbial risks associated with the type of egg production systems (large‐scale commercial, small‐scale commercial, and village). The survey evaluated the following aspects: level of microbial contamination risk; possible source (s) of contamination; likelihood and mode of contamination (“vertical”, “mechanical” or “both”); ranking of eight common eggshell‐associated pathogens; likely existence of pathogens that could cause food safety problems in humans in general and specifically in a SSA village; the microbial risks of the inclusion of ground chicken eggshells in commonly eaten foods in central Tanzania; and the likelihood that the proposed preparation method for eggshell powder would be a risk. Experts were also asked to comment on the proposed method for preparing eggshell powder in relation to food safety risks. The two‐round survey was conducted on the online platform SurveyMonkey, over 5 months. Each round was open for 2 weeks. A summary of initial round responses was sent to panellists by email to consider before they participated in the second round. Consensus measurement began in the second round with 80% agreement required for consensus. The responses “Do not know” and “Uncertain” were combined for analysis. Qualitative data from the e‐Delphi survey were organised into themes with similar statements. Quantitative data were collated using Microsoft Excel 2013 (Microsoft Corp., USA) and analysed using SPSS Statistics version 22 (IBM Corporation, USA). In the initial round, 4‐point Likert‐scale questions were described as median, 25th and 75th percentiles and range. The ranking of pathogens was expressed as count. Five focus group discussions (FGDs) to investigate the concept, acceptability, and practicality of ground eggshell for human consumption were conducted in January 2017 in five villages in Iwondo Ward, Mpwapwa District, Dodoma Region, Tanzania. These wards were selected for the overall study by the larger projects’s Country Coordinating Committee based on: the level of child undernutrition; an absence of existing nutrition‐oriented interventions; and a willingness by leaders at the regional, district, and ward level to be involved. Recruitment to the groups was undertaken by community leaders in each village who invited available women at random. The purpose and nature of the study was explained to the participants and written consent obtained. Participants were provided with a complimentary meal after the discussion group. Each discussion group was held in a neutral location in the village. Discussions were facilitated by an investigator in a semi‐structured format in English with simultaneous Swahili translation. All of the FGDs were audio‐recorded and later transcribed and translated. The investigator made fieldnotes on the non‐verbal interactions of the participants during the discussions. Questions were related to normal practice of food preparations, egg consumption and uses, acceptability, and practicality of preparing and using ground eggshell (Appendix S1). Analysis of the transcripts was carried out by manual coding and thematic analysis (Braun & Clarke, 2006). Codes were drawn out from the transcripts in an inductive manner. From these initial codes, the data were then grouped into broad themes to provide a basis for further subtheme analysis using Microsoft Excel 2013 (Microsoft Corp., USA). The investigator’s field notes on non‐verbal communication and behaviour during the discussion groups were used to supplement the transcript data across the major themes. Ethical approval for the e‐Delphi survey was provided by the Human Research Ethics Committee (HREC) as an amendment to the broader project to which this study contributes, “Strengthening food and nutrition security through family poultry and crop integration in Tanzania and Zambia” (National Institute of Medical Research in Tanzania, NIMR/HQ/R.8a/Vol.IX/1690; University of Sydney, HREC #2014/209). The focus group research was approved by the Clinical Research and Ethical Review Board at the Royal Veterinary College (#2016/1612).
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