Dietary fumonisin exposure in a rural population of South Africa
Introduction
The fumonisin B (FB) mycotoxins are ubiquitous contaminants of maize mainly produced by the fungi Fusarium verticillioides and F. proliferatum (Rheeder et al., 2002). They are known to cause several diseases in animals and are associated with a high incidence of human oesophageal and liver cancer in certain geographical areas of the world (Rheeder et al., 1992, Ueno et al., 1997), as well as the development of neural tube defects (Marasas et al., 2004). To date about 28 fumonisins have been identified (Rheeder et al., 2002). FB1, the most abundant occurs together with FB2 and FB3 mainly in maize with levels varying with season and geographical location (Shephard et al., 1996, Rheeder et al., 2002). The fumonisins have been classified as group 2B carcinogens (possibly carcinogenic to humans) by the International Agency for Research on Cancer (IARC, 2002). A group provisional maximum tolerable daily intake (PMTDI) for fumonisins (B1, B2 and B3) of 2 μg kg−1 bw day−1 was established by the Joint FAO/WHO Expert Committee on Food Additives (JECFA), using a no observed adverse effect level (NOAEL) of 0.2 mg kg−1 bw day−1 for nephrotoxicity in rats and a safety factor of 100 (Bolger et al., 2001).
The risk of exposure to mycotoxins in human populations residing in developing countries are considered to be far greater where the implementation of legislative control is compromised due to many economic, political and environmental factors (Wagacha and Muthomi, 2008, WHO, 2006). In South Africa, the former Transkei region of the Eastern Cape Province (EC) is a rural area characterised by a high prevalence of poverty and underdevelopment. The majority of the inhabitants are dependent on governmental pensions and grants while migrant labourers provide an additional income (D’Haese and Van Huylenbroeck, 2005, Nel and Davies, 1999). Subsistence farming is a major source of food security where the daily intake of maize is part of a culturally distinct dietary pattern and ethnic tradition. Home-grown maize from these areas is known to be contaminated with high levels of fumonisin and therefore poses an important health risk (Shephard et al., 2007). Commercial maize also consumed in these areas, generally contains far lower fumonisin levels, but could still pose a risk if consumed in large quantities. The determination of fumonisin exposure, which forms an integral part of the human risk assessment process, is therefore of critical importance. However, the lack of any regulations or monitoring of fumonisin levels in South African maize intended for human consumption further contributes to the uncertainty when determining risk (Gelderblom et al., 2008, Marasas et al., 2008).
The accuracy of assessing mycotoxin exposure is not only dependent on standardised analytical methods to determine the level of contamination in the food matrix, but also on detailed dietary intakes using effective and validated dietary assessment instruments (Kroes et al., 2002). In South Africa the national food consumption survey together with a few demographic-specific consumption studies provide limited data on maize consumption in rural areas (National Food Consumption Survey, 2000, Nel and Steyn, 2002). In a population at risk to fumonisin exposure, the maize intakes together with the maize-dietary practices will influence exposure. Factors such as the sources of maize, mixture of maize with other food components, seasonal variations of these components, socio-economic status, cultural traditions, food preparations, food availability and accessibility will impact on maize consumption. To address the methodological challenges of estimating dietary mycotoxin intake, a culturally specific dietary assessment tool, the Ratio And Portion size Photo (RAPP) tool was developed and validated among a black Xhosa-speaking African rural population (Wolmarans and Wentzel-Viljoen, 2008).
In the present study, the RAPP tool was used to assess maize consumption patterns and consequently fumonisin exposure in Centane, an area in the EC of South Africa where maize is consumed as a major dietary staple. This rural area is known for its high incidence of oesophageal cancer (OC) while the home-grown maize is highly contaminated with the fumonisin B mycotoxins (Somdyala et al., 2003, Shephard et al., 2007).
Section snippets
Study population
Ethical approval for the study was granted by the South African Medical Research Council Ethics Committee. Three hundred and fifteen apparently healthy volunteers between the ages of 18 and 70 were recruited after informed and signed consent. Volunteers were recruited from 21 rural villages within the magisterial area of Centane, Amathole District Municipality in the EC. A field laboratory was set up at three local trading stores along a central road, providing easy access to participants.
Characteristics of the study population
The mean values of the different parameters are the geometric mean with the 95% confidence interval (CI). Eighty-three percent of the study population (n = 315) were women (n = 261). Anthropometric variables included a mean body mass index of 27 kg/m2 (95% CI: 26–28) and a mean weight of 68 kg (95% CI: 67–70). The mean age and years of residence in the EC were 42 years (95% CI: 41–44) and 40 years (95%CI: 38–41), respectively. Socio-economic parameters indicated that a river or dam was the main source
Discussion
Human exposure to fumonisins in a rural area of Centane involves comprehensive analysis not only of the level of fumonisin contamination but also of the distinct maize-dietary patterns. Typical maize-dietary practises of people living in these rural areas includes hand grinding utilising “grinding” rocks or stamping of home-grown maize to produce maize meal or samp (Rose, 1972, Grobbelaar and Bateman, 1991). The resultant maize meal is either used for the preparation of porridges with different
Conflict of Interest
The authors declare that there are no conflicts of interest.
Acknowledgements
The authors would like to thank the funders of this study, the Cancer Association of South Africa (CANSA) and the Medical Research Council (MRC). The following persons: Ms. Lorna Thomas, research nurse; Mr. John Mokotary, driver and technical assistant as well as the fieldworkers Ms. Nokhutula Kulati, Ms. Bongiwe Kulati, Ms. Nobobele Mpetsheni and Ms. Beauty Stampu. Also, a special thanks to the Hulley family, trading store owners in Centane and the staff of the Trennery’s Hotel, Qolora for
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2019, Food ControlCitation Excerpt :Subsequent studies in Centane have arrived at similar intake values. Shephard et al. (2007), using weighed food quantities, calculated mean maize intakes of 483 g/adult male per day and 428 g/adult female per day, whereas Burger et al. (2010), using a culturally specific ratio and portion size photo (RAPP) tool, estimated intakes among the group consuming both commercial and home-grown maize to be 632 g/day for males and 440 g/day for females. Another estimate, based on the data of Nel and Steyn (2002) from other rural areas of South Africa and a number of assumptions to convert cooked food into dry maize intake, arrived at a daily maize consumption of 461 g/person (Shephard et al., 2007).