Vitamin A content and bio-availability of South African maize meal (as purchased and consumed)

Abstract

In 2003 the Department of Health of South Africa embarked on a mandatory fortification programme of maize meal as part of the Integrated Nutrition Program (INP) to alleviate malnutrition. The aim of this study was two-fold: firstly, to determine the vitamin A content of South African fortified white maize meal as purchased and the maize porridge as traditionally prepared from it as consumed and secondly, to determine the relative efficacy of the daily consumption of maize meal in sustaining or improving vitamin A status. Maize meal samples for analysis were purchased from various supermarkets and small retail outlets. A High Performance Liquid Chromatograph-Diode Array Detector system with a Reverse Phase C-18 column and isocratic elution was used for separation and quantification of vitamin A. The highest mean vitamin A concentration measured in the maize meal was 261 μgRE/100g and the lowest mean vitamin A concentration was <19 μgRE/100g. Pertaining to the regulations the final minimum level of vitamin A in fortified maize meal must not be less than 187.7 μgRE/100g. The average retention of vitamin A in maize porridge as the difference in vitamin A concentration measured between raw maize meal and cooked porridge was calculated at 39.8%. One of the considerations in a fortification program is the availability of certain micronutrients in the fortified foods, with the focus in this project on vitamin A. An animal model, namely chickens, closely relating the metabolism of vitamin A in humans was used. Chickens are very susceptible to vitamin A deficiencies with similar symptoms. Growth and vitamin A status was evaluated by the weight, feed conversion and liver retinol stores of chickens on five different maize based diets over a six week period. No significant difference in vitamin A levels in the livers of birds on diets with fortified white maize meal, compared to the normal poultry diet consisting of yellow maize meal with added vitamin A was found. It can thus be concluded that the fortificant in the white maize meal is as bioavailable as the vitamin A in the premix used in poultry nutrition. The results of this study show that the vitamin A added as fortificant is absorbed and available to the body. Therefore, fortification of commonly eaten staple foods in the country can significantly improve the vitamin A intake of the population and will improve the overall micronutrient density of their diets. Fortification should be set at levels to include losses incurred through packaging and during transportation, shelf losses and preparation losses. It is also important that the vitamin A content of the product as purchased and consumed must be regularly monitored and regulated by government. Valid and reliable evaluation data are needed to evaluate a program’s success, and to make timeous adjustments for optimal efficiency.