Estimates of Dietary Mineral Supply in Malawi Based on Soil Type and Household Survey Data
Edward Joy *
University of Nottingham, Nottingham, UK and British Geological Survey, Nottingham, UK.
Martin Broadley
University of Nottingham, Nottingham, UK.
Michael Watts
British Geological Survey, Nottingham, UK.
Allan Chilimba
Ministry of Agriculture and Food Security, Mzuzu, Malawi.
Scott Young
University of Nottingham, Nottingham, UK.
Louise Ander
British Geological Survey, Nottingham, UK.
Colin Black
University of Nottingham, Nottingham, UK.
*Author to whom correspondence should be addressed.
Abstract
Objectives: Mineral deficiencies due to inadequate dietary supply are likely to be widespread in Malawi. However, there is insufficient reliable data on mineral supplies and deficiency risks at scales useful for policy-makers. This study provides mineral supply estimates at the level of Extension Planning Area (EPA).
Methods: Food samples were collected and analysed by inductively coupled plasma mass spectrometry (ICPMS) to generate a national food mineral composition database for Malawi according to soil type. Composition data were combined with food consumption data from the Third Malawi Integrated Household Survey in order to provide spatially-disaggregated dietary mineral supply estimates.
Results: There is great regional variation in dietary mineral supplies due to soil type and dietary choices. On "calcaric" soils, the national average diet contains 791 mg Ca, 77 µg Se and 14 mg Zn, while on "non-calcaric" soils the average diet contains 715 mg Ca, 36 µg Se, and 11 mg Zn. Supplies of Ca by EPA ranged from 123 mg to > 2000 mg capita-1 d-1, while Se ranged from 10 µg to > 100 µg and Zn from 4.4 mg to > 20 mg. Fish provide 52, 38 and 22% of all Ca, Se and Zn supplies, respectively, in the national average diet.
Conclusions: Our estimates of spatially-disaggregated dietary mineral supplies can guide policy-makers in designing region-specific nutrition interventions.