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Wageningen Universiteit (2007)

Towards a food-based approach to improve iron and zinc status of rural Beninese children : enhancing mineral bioavailability from sorghum-based food

Mitchikpe, C.E.S.

Titre : Towards a food-based approach to improve iron and zinc status of rural Beninese children : enhancing mineral bioavailability from sorghum-based food

Auteur : Mitchikpe, C.E.S.

Université de soutenance : Wageningen Universiteit

Grade : Doctor of Philosophy (PhD) 2007

Résumé
Pre-school children are stunted and more than 70 % are anaemic. Prevalence rates of iron and zinc deficiencies are also expected to be high. The poor nutritional status of Beninese children might be due to low energy and nutrient intakes and to inhibiting effects of antinutritional factors such as phytate and polyphenols on iron and zinc bioavailability from the diet.
Objective. To study growth performance and iron and zinc status of rural Beninese school-age children in relation to their actual food consumption pattern and in relation to the iron and zinc bioavailability from their foods.
Methods : Eighty children aged 6 to 8 years were random !y selected from 3 villages in northern Benin and were studied in a post-harvest and a pre-harvest season. Nutritional status was assessed by anthropometry and blood analyses, and their food consumption was assessed by an observed weighed record method. Chemical analyses were performed in 23 samples of most frequently consumed foods. The potentially inhibiting effect of phytate on iron and zinc bioavailability from these foods was estimated using phytate/iron and phytate/zinc molar ratios. The effect of various food processing methods on iron and zinc solubility and on iron bioavailability from a commonly consumed food (dibou) was studied using an in vitro digestion/Caco-2 cell model.
Results : In the post-harvest season, Z-scores for height-for-age and for weight-for-height were -1.72±0.89 and -0.89_+0.62, respectively. Obviously, the children were stunted but not wasted. Seasonal variation in growth performance was only marginal. In post-harvest season haemoglobin and serum ferritin levels were 119±I3 g/1 and 43±31 ugl. Haemoglobin level was significantly decreased by 7 g/1 from the post- to the pre-harvest season (P<0.01). Prevalence of iron deficiency was high : 49 and 33 % in the post- and pre-harvest season, respectively. Serum zinc level was 17.9±4.6 um ?l/ ?. So, zinc status seemed to be normal. The children consumed a plant-based diet. The observed seasonal variation in food pattern did not really result in seasonality in energy and nutrient intakes. Cereals (maize, sorghum and millet) contributed to 43 % (post-harvest season) and 55 % (pre-harvest season) of the daily energy intake. Daily energy intakes were 5.2±1.4 and 5.4±1.3 MJ in the post- and pre-harvest season, respectively. Although energy and nutrient intakes seemed to be adequate, the diet was not well balanced and was low in animal products, protein, fat and vitamin C and high in fibre. In cereals, phytate/iron and phytate/zinc molar ratios ranged from 1 to 11 and 3 to 22, respectively. Such molar ratios indicate poor iron and zinc bioavai !ability. Dephytinisation (using an exogenous phytase) and dehulling resulted in an increased iron and zinc solubility in dibou and in a 10 % higher iron bioavailability from dibou when compared to dibou prepared from whole grains. Pounded grains soaked for 1 and 3.5 h did not show positive effects. However, none of the effects of food processing methods on iron bioavailability reached statistical significance.
Conclusion : SchooI-age children in northern Benin have a poor growth performance and many of them can be classified as stunted. This suggests that these children suffer from a long-term marginal food intake, quantitatively and qualitatively. This is confirmed by the food intake results which underline that the iron and zinc bioavailability is poor because of the presence of high levels of antinutritional factors as phytate and polyphenols. The low iron bioavailability is undoubtedly one of the causes of the high prevalence rate of anaemia among these children. To improve the iron and zinc status of the children, further reductions of phytate and phenolic compounds in the food might be warranted.

Mots clés : nutritional state - zinc - iron - bioavailability - sorghum - tropical foods - mineral deficiencies - children - benin

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Page publiée le 14 septembre 2007, mise à jour le 14 janvier 2018