Volume 90, Issue 3, September (2003), pp. 521-527 © The Author 2003
doi:10.1079/BJN2003923

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The leafy vegetable amaranth (Amaranthus gangeticus) is a potent inhibitor of calcium availability and retention in rice-based diets

Torben Larsen¹, Shakuntala H. Thilsted², Sunil K. Biswas³, Inge Tetens^2
1Department of Animal Health and Welfare, Danish Institute of Agricultural Sciences, Research Centre Foulum, PO Box 50, 8830 Tjele, Denmark
²Department of Human Nutrition, The Royal Veterinary and Agricultural University, Rolighedsvej 30, 1958 Frederiksberg, C, , Denmark
³Grain Quality and Nutrition Division, Bangladesh Rice Research Institute, Gazipur 1701, Bangladesh

 (Received 17 September 2002–Revised 28 March 2003–Accepted 29 April 2003)

Improvement in the nutritional quality of Bangladeshi rice-based diets is sought through increasing the amounts of vegetables, fish and legumes consumed. The aim of the present study was to compare the effects of rice-based diets on selected parameters of Ca and P availability and retention in young, growing rats. The study was designed as a randomised balance trial with five diets, eight animals per diet, and two balance periods of 1 week each. Apart from diet 1, which was a pure rice diet, the other four diets were composite diets and included the leafy vegetable, amaranth leaves (Amaranthus gangeticus), the small fish, mola (Amblypharyngodon mola), and lentils (Lens culinaris) in different amounts to simulate the average rural rice-based diet, the recommended diet, the recommended diet diluted with starch, and the recommended diet excluding amaranth leaves. The inclusion of amaranth leaves, mola and lentils significantly improved N and growth retention in the rats compared with the pure rice diet. However, a minor addition of amaranth (0·66 g/100 g DM) significantly reduced the fractional Ca absorption and retention. Femur bone mass and Ca and P densities were significantly lower in the rats fed the diets that included amaranth leaves. The observed inhibitory effect of the amaranth leaves on Ca absorption and utilisation was probably due to the oxalate content. It is concluded that the formulation of a recommended diet cannot be based only on nutrient content values of individual food components due to interactions between nutrients and anti-nutrients in the diet.

Keywords:
Food and nutrition security, Micronutrient deficiency, Anti-nutrients, Mineral bioavailability, Small fish

Abbreviations:
OM, organic matter