SEGH Articles

Mapping Hidden Hunger in Malawi

14 February 2016
Maps for Malawi predict spatial variation in the dietary supply of seven essential elements (calcium, copper, iodine, iron, magnesium, selenium and zinc).

Edward Joy and Louise Ander describe how recently created maps of Malawi predict spatial variation in the dietary supply of seven essential elements (calcium, copper, iodine, iron, magnesium, selenium and zinc). These maps combine information on soil and crop properties, household dietary choices and socio-economic factors. This information can help to identify key controls on mineral micronutrient dietary deficiencies – also known as “hidden hunger” – and identify research priorities for the development of appropriate and feasible interventions to reduce population-wide hidden hunger.


Life in Malawi

Malawi is a land-locked country in south-east Africa. The majority of households rely on subsistence farming with typical land size ~2 ha. Average Gross National Income is just USD 308 capita-1 compared to USD 42,098 capita‑1 in the UK. In this context, the quality of diets is affected by the ability of households to grow sufficient, nutritious food, and to supplement this with purchases. Typically, households devote most of their land to the staple crop maize which is a rational strategy when the primary objective is to satisfy energy requirements. If land and other resources such as labour permit, households may also grow legumes, vegetables, fruits etc. and some grow tobacco as a cash crop.

Hunger, or fear of hunger, is a common concern for most Malawian households. Yet hidden hunger, meaning inadequate vitamin or mineral intakes, is even more widespread. For example, zinc deficiency contributes to a very high stunting rate of 48% of children in rural areas. Food insecurity is one reason why life expectancy at birth is ~55 years, similar to that in the UK 100 years ago. Better data and an improved understanding of diets and nutrition is important to inform health and agriculture policies. We matched food consumption data recorded in a recent national household survey with crop composition data refined by soil type to quantify and map dietary mineral supplies and deficiencies across Malawi.


Not only “hidden” hunger…..

Most smallholder farmers rely on manual labour and hence have active lifestyles. As part of this study, we show that energy supplies are likely to be inadequate to support active lifestyles in >50% of households. This observation is supported by the finding that as incomes increase, there is no proportional decrease in spending on food. This suggests that those lowest income households are short of essential food.


Seasonal intakes of vegetables cause fluctuation of dietary mineral supply….

Most of Malawi has one long growing (rainy) season from December to April. Subsistence farming results in a change in availability and consumption of pulses, fruits and vegetables (including the leaves of edible ‘weeds’), which are consumed more frequently at the end of the rainy season. This leads to seasonal variation in the dietary supply of essential trace elements.


River and lake fish improve dietary micronutrient supply…..

The most commonly-consumed animal product is fish, mainly sourced from Lake Malawi and Lake Chilwa. Fish consumption is greater in households close to the major lakes and this leads to greater consumption of several micronutrients, particularly calcium, selenium and zinc.

Wealthier households have healthier diets, but soil type has the greatest control over selenium supplies…..

Household wealth was negatively associated with risk of deficiency for all nutrients studied. This is due to greater consumption of foods including micronutrient-rich animal-source foods. Previous research has shown that calcareous soils in Malawi result in higher crop selenium concentrations. Here we show that the effect of soil type is more important than household wealth in providing beneficial increases in dietary selenium supply.

 

What next?

Ensuring food security in Malawi remains a huge challenge but there are possible interventions to improve dietary mineral supplies. Interventions can be successful, e.g. the national salt iodisation programme which is responsible for the majority of the dietary supply of iodine in Malawi (as with many other countries globally). There are crop breeding programmes to increase micronutrient concentrations, particularly for zinc. Selenium could be increased in crops through enriched fertilisers, as shown in experimental trials in Malawi conducted on soils with low inherent selenium availability. Fertiliser fortification is being successfully used as a national approach to increasing dietary selenium supply in Finland.

Further information

You can read our open access paper if you would like find out more, including the full set of maps we have generated for Malawi.

This work was one of the outputs of Edward’s PhD, as well as that of the ongoing PhD project of Diriba Kumssa. Dr Edward Joy was supervised by Prof. Martin Broadley, Dr Scott Young, the late Prof. Colin Black (School of Biosciences, University of Nottingham (UoN)), Dr Louise Ander, Dr Michael Watts (British Geological Survey (BGS)) and Dr Allan Chilimba (Ministry of Agriculture and Irrigation, Malawi), with PhD funding from UoN and BGS.

Edward’s PhD research is part of an ongoing programme of research in the Centre for Environmental Geochemistry (School of Biosciences, UoN and Inorganic Geochemistry, BGS) alongside our fantastic wider network of research partners in Malawi, and beyond.

Our most recent activity is the initiation of the Royal Society – Department for International Development (RS-DFID) Africa Capacity Building project “Strengthening African capacity in soil geochemistry” in Malawi, Zambia and Zimbabwe. We have recently welcomed 5 new PhD students into this 5 year project, two of whom will directly build upon outputs from Edward’s PhD, with plans for more! Edward is now working at the London School of Hygiene Tropical Medicine (LSHTM).

by Edward Joy and Louise Ander

 

 

Keep up to date

Submit Content

Members can keep in touch with their colleagues through short news and events articles of interest to the SEGH community.

Science in the News

Latest on-line papers from the SEGH journal: Environmental Geochemistry and Health

  • Improving arsenopyrite oxidation rate laws: implications for arsenic mobilization during aquifer storage and recovery (ASR) 2018-04-25

    Abstract

    Aquifer storage and recovery (ASR) and aquifer recharge (AR) provide technical solutions to address water supply deficits and growing future water demands. Unfortunately, the mobilization of naturally present arsenic due to ASR/AR operations has undermined its application on a larger scale. Predicting arsenic mobility in the subsurface during ASR/AR is further complicated by site-specific factors, including the arsenic mobilization mechanisms, groundwater flow conditions, and multi-phase geochemical interactions. In order to ensure safe and sustainable ASR/AR operation, a better understanding of these factors is needed. The current study thus aims to better characterize and model arsenic remobilization at ASR/AR sites by compiling and analyzing available kinetic data on arsenic mobilization from arsenopyrite under different aqueous conditions. More robust and widely applicable rate laws are developed for geochemical conditions relevant to ASR/AR. Sensitivity analysis of these new rate laws gives further insight into the controlling geochemical factors for arsenic mobilization. When improved rate laws are incorporated as the inputs for reactive transport modeling, arsenic mobilization in ASR/AR operations can be predicted with an improved accuracy. The outcomes will be used to guide groundwater monitoring and specify ASR/AR operational parameters, including water pretreatment requirements prior to injection.

  • Heavy metal exposure has adverse effects on the growth and development of preschool children 2018-04-25

    Abstract

    The purpose of this study was to investigate the associations between levels of lead (Pb), cadmium (Cd), chromium (Cr), and manganese (Mn) in the PM2.5 and blood and physical growth, and development parameters including birth length and weight, height, weight, body mass index (BMI), head circumference, and chest circumference in preschool children from Guiyu (e-waste exposure area) and Haojiang (the reference area). A total of 470 preschool children from Guiyu and Haojiang located in southeast coast of China were recruited and required to undergo physical examination and blood tests during the study period. Birth length and weight were obtained by birth records and questionnaire. Pb and Cd in both PM2.5 and blood were significantly higher in Guiyu than Haojiang. Remarkably, the children of Guiyu had significantly lower birth weight and length, BMI, and chest circumference when compare to their peers from the reference area (all p value < 0.05). Spearman correlation analyses showed that blood Pb was negatively correlated with height (r = −0.130, p < 0.001), weight (r = −0.169, p < 0.001), BMI (r = −0.100, p < 0.05), head circumference (r = −0.095, p < 0.05), and chest circumference (r = −0.112, p < 0.05). After adjustment for the potential confounders in further linear regression analyses, blood Pb was negatively associated with height (β = −0.066, p < 0.05), weight (β = −0.119, p < 0.001), head circumference (β = −0.123, p < 0.01), and chest circumference (β = −0.104, p < 0.05), respectively. No significant association between blood Cd, Cr, or Mn was found with any of our developmental outcomes. Taken together, lead exposure limits or delays the growth and development of preschool children.

  • Contamination characteristics of trace metals in dust from different levels of roads of a heavily air-polluted city in north China 2018-04-24

    Abstract

    Concentrations of eight trace metals (TMs) in road dust (RD) (particles < 25 μm) from urban areas of Xinxiang, China, were determined by inductively coupled plasma mass spectrometry. The geometric mean concentrations of Zn, Mn, Pb, As, Cu, Cr, Ni and Cd were 489, 350, 114, 101, 60.0, 39.7, 31.6, and 5.1 mg kg−1, respectively. When compared with TM levels in background soil, the samples generally display elevated TM concentrations, except for Cr and Mn, and for Cd the enrichment value was 69.6. Spatial variations indicated TMs in RD from park path would have similar sources with main roads, collector streets and bypasses. Average daily exposure doses of the studied TMs were about three orders of magnitude higher for hand-to-mouth ingestion than dermal contact, and the exposure doses for children were 9.33 times higher than that for adults. The decreasing trend of calculated hazard indexes (HI) for the eight elements was As > Pb > Cr > Mn > Cd > Zn > Ni > Cu for both children and adults.