Intakes of foods most commonly consumed : secondary data analyses of South African food consumption studies (1983-2000)

Nel, Johanna Helena (2002-12)

Thesis (MBA) -- Stellenbosch University, 2002.

Thesis

ENGLISH ABSTRACT: The role of the Global Environment Monitoring System / Food Contamination Monitoring and Assessment Programme (GEMS/Food) is to assess and inform governments, the Codex Alimentarius Commission and other relevant institutions, as well as the public, on levels and trends of contaminants in food, their contribution to total human exposure, and their significance with regard to public health and trade. The primary objective of this study is to generate a reference list of “most commonly” consumed food items and average intakes of these items in the diet of South Africans, using GEMS/Food specifications. The list is required to be representative of foods eaten by children and adults from all age and ethnic groups in South Africa. The list will serve as a reference for the Department of Health who will undertake analyses of (a) toxic chemicals, such as pesticides, heavy metals and environmental contaminants; (b) naturally occurring toxins; and (c) food additives in the commonly consumed food items, as required by the Codex Alimentarius Commission. A secondary objective of the study is to derive average (mean) weights of South Africans in different age groups in order for the calculation of dietary exposure of selected contaminants. Secondary data-analysis was conducted on existing dietary databases (raw data) obtained from surveys undertaken in South Africa between 1983 and 2000. The National Food Consumption Survey (NFCS) served as a framework for compiling data on children since this was a national representative survey of 1 to 9 year-old children in South Africa. However there has never been a national dietary survey on adults in South Africa. Consequently the data had to be extrapolated from existing isolated surveys on adults. The dietary intake for the groups 1 to 5 years and 6 to 9 years was calculated only from the NFCS, and was not supplemented by other databases. The substantiation for treating age 10+ as a unit (and calling it an adult group), was the finding that average consumption of adolescents (10 – 15 years) did not differ significantly from that of adults when comparing mean energy intakes and mean quantities consumed, of age groups in the studies analysed. Data were analysed in terms of the percentage of the group consuming specific food main groups / subgroups / food items and on average per capita portion size. Factor analyses were done to analyse the inter-relationships among the food consumption patterns of NFCS 6-9 year-olds in 9 provinces, urban and rural separately, and the inter-relationships among food consumption patterns of these children and other children and adults in other independent food consumption studies. Two methods of estimating adult consumption were derived. The results from Method 1 corresponded with results from the NFCS, which was over-sampled for lower socio-economic areas, whereas the results from Method 2 ignored relationships with NFCS data and were based on the ethnic proportions of the population in South Africa. A final list, validated against international data, is included, which provides the per capita consumption per food item, average amount consumed (consumers only), the 97,5th percentile of the consumption figures (consumers only), as well as the corresponding gram per kilogram body weight consumed. These figures represent food items consumed by 3% or more of the South African population, for the following age groups: 1-5 years, 6-9 years and age 10+ (adults). Also, average weights of South Africans for the corresponding age groups are provided, which is calculated similarly to the methods used to calculate dietary intake.

AFRIKAANSE OPSOMMING: Die rol van die “Global Environment Monitoring System / Food Contamination Monitoring and Assessment Programme”, of (GEMS/Food), is om regerings, die “Codex Alimentarius”, ander relevante instellings en die publiek, op hoogte te hou (en selfs te monitor), ten opsigte van vlakke en neigings van kontaminasie in voedsel, die omvang van blootstelling aan die mens, en die beduidendheid hiervan vir openbare gesondheid en handel. Die doel van hierdie studie is om ‘n lys van voedselitems wat meestal deur die Suid- Afrikaanse bevolking geëet word, op te stel. Die lys moet hoeveelhede wat ingeneem word reflekteer, en moet aan die GEMS/Food spesifikasies voldoen. Dit moet verteenwoordigend wees van kos wat kinders en grootmense, van alle ouderdomsgroepe en rassegroepe in Suid- Afrika eet. Hierdie lys sal as verwysing vir die Departement van Gesondheid dien, om sodoende dan die berekenings van (a) toksiese chemikalië, soos plaagbeheermiddels, swaar metale en omgewingsbesoedelingsagente; (b) toksine wat natuurlik voorkom; en (c) voedselaanvullings in kossoorte, soos voorgeskryf deur die “Codex Alimentarius Commission”, te bereken. ‘n Sekondêre doel van hierdie studie is om die gemiddelde gewig van Suid-Afrikaners vir verskillende ouderdomsgroepe te bereken, om gebruik te word vir die berekenings van blootstelling aan geselekteerde toksine en besoedelingsagente. Sekondêre data-analise is op bestaande diëetkundige databasisse (oorspronklike data), wat opnames in Suid-Afrika vir die tydperk 1983 tot 2000 verteenwoordig, uitgevoer. Die Nasionale Voedselverbruikersopname, “National Food Consumption Survey” (NFCS), dien as raamwerk om die verbruik van kinders saam te stel, want hierdie opname was ‘n nasionaalverteenwoordigende opname van kinders van die ouderdom 1-9 jaar in Suid-Afrika. Daar was egter tot nou toe nog nie ‘n nasionaal-verteenwoordigende opname van voedselverbruik vir volwassenes in Suid-Afrika nie. Gevolglik moet hierdie data vanuit geïsoleerde opnames op volwassenes onttrek word. Voedselinname van kinders van ouderdomsgroepe 1-5 jaar en 6-9 jaar is dus bereken deur van die NFCS data gebruik te maak sonder aanvulling van enige ander databasisse. Die motivering om kinders van die ouderdomsgroep 10+ te hanteer in dieselfde groep as volwassenes, was die bevinding dat gemiddelde verbruik van adolessente (10 – 15 jaar) nie beduidend verskil het van die van volwassenes nie, veral as daar na die kilojoule inname en die hoeveelheid (gemeet in gram) inname, gekyk word. Die data van die verskeie opnames is ge-analiseer in terme van die persentasie verbruikers en die per kapita inname per voedselsoort, gegroepeerd en ongegroepeerd. Verbande tussen NFCS 6-9 jaar data in die 9 provinsies, landelike en stedelike gebiede afsonderlik beskou, asook verbande tussen hierdie kinders en kinders en volwassenes in onafhanklike ander opnames is met behulp van faktorontledings vasgestel. Twee metodes waarmee die voedselinnames van volwassenes voorspel kan word, is afgelei. Die resultate van Metode 1 stem met die resultate van die NFCS ooreen, waar die aanname is dat daar in die steekproefneming meer op kinders van laer sosio-ekonomiese areas gekonsentreer is. Metode 2 se resultate is gebaseer op die etniese verspreiding van die rassegroepe in Suid-Afrika, en voedselinnames van die blankes, byvoorbeeld, word meer in ag geneem. Die finale lys van voedselsoorte, wat gevalideer is teenoor ander internasionale studies, sluit die volgende veranderlikes in: die per kapita verbruik van die items, die gemiddelde verbruik per item (deur net die verbruikers van die spesifieke item in ag te neem), die 97,5de persentiel van voedselitems wat bereken is vir die groep wat die voedselitem verbruik, en ook die gram (gebaseer op die 97,5de persentiel verbruikers) per kilogram ligaamsgewig verbruik vir hierdie items. Hierdie syfers is vir voedselitems wat deur 3% of meer van die verbruikers in Suid-Afrika geneem word, en vir die volgende ouderdomsgroepe: 1-5 jaar, 6-9 jaar vir die ouderdom 10+ . Die gemiddelde gewig van Suid-Afrikaners vir die ooreenstemmende ouderdomsgroepe is ook bereken deur van dieselfde tegnieke gebruik te maak as die waarmee die voedselinnames bereken is.

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