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

  • Ecological impact of the antibiotic ciprofloxacin on microbial community of aerobic activated sludge 2019-08-16


    This study investigated the effects and fate of the antibiotic ciprofloxacin (CIP) at environmentally relevant levels (50–500 µg/L) in activated sludge (AS) microbial communities under aerobic conditions. Exposure to 500 µg/L of CIP decreased species diversity by about 20% and significantly altered the phylogenetic structure of AS communities compared to those of control communities (no CIP exposure), while there were no significant changes upon exposure to 50 µg/L of CIP. Analysis of community composition revealed that exposure to 500 µg/L of CIP significantly reduced the relative abundance of Rhodobacteraceae and Nakamurellaceae by more than tenfold. These species frequently occur in AS communities across many full-scale wastewater treatment plants and are involved in key ecosystem functions (i.e., organic matter and nitrogen removal). Our analyses showed that 50–500 µg/L CIP was poorly removed in AS (about 20% removal), implying that the majority of CIP from AS processes may be released with either their effluents or waste sludge. We therefore strongly recommend further research on CIP residuals and/or post-treatment processes (e.g., anaerobic digestion) for waste streams that may cause ecological risks in receiving water bodies.

  • Source and background threshold values of potentially toxic elements in soils by multivariate statistics and GIS-based mapping: a high density sampling survey in the Parauapebas basin, Brazilian Amazon 2019-08-10


    A high-density regional-scale soil geochemical survey comprising 727 samples (one sample per each 5 × 5 km grid) was carried out in the Parauapebas sub-basin of the Brazilian Amazonia, under the Itacaiúnas Basin Geochemical Mapping and Background Project. Samples were taken from two depths at each site: surface soil, 0–20 cm and deep soil, 30–50 cm. The ground and sieved (< 75 µm) fraction was digested using aqua regia and analyzed for 51 elements by inductively coupled plasma mass spectrometry (ICPMS). All data were used here, but the principal focus was on the potential toxic elements (PTEs) and Fe and Mn to evaluate the spatial distribution patterns and to establish their geochemical background concentrations in soils. Geochemical maps as well as principal component analysis (PCA) show that the distribution patterns of the elements are very similar between surface and deep soils. The PCA, applied on clr-transformed data, identified four major associations: Fe–Ti–V–Sc–Cu–Cr–Ni (Gp-1); Zr–Hf–U–Nb–Th–Al–P–Mo–Ga (Gp-2); K–Na–Ca–Mg–Ba–Rb–Sr (Gp-3); and La–Ce–Co–Mn–Y–Zn–Cd (Gp-4). Moreover, the distribution patterns of elements varied significantly among the three major geological domains. The whole data indicate a strong imprint of local geological setting in the geochemical associations and point to a dominant geogenic origin for the analyzed elements. Copper and Fe in Gp-1 were enriched in the Carajás basin and are associated with metavolcanic rocks and banded-iron formations, respectively. However, the spatial distribution of Cu is also highly influenced by two hydrothermal mineralized copper belts. Ni–Cr in Gp-1 are highly correlated and spatially associated with mafic and ultramafic units. The Gp-2 is partially composed of high field strength elements (Zr, Hf, Nb, U, Th) that could be linked to occurrences of A-type Neoarchean granites. The Gp-3 elements are mobile elements which are commonly found in feldspars and other rock-forming minerals being liberated by chemical weathering. The background threshold values (BTV) were estimated separately for surface and deep soils using different methods. The ‘75th percentile’, which commonly used for the estimation of the quality reference values (QRVs) following the Brazilian regulation, gave more restrictive or conservative (low) BTVs, while the ‘MMAD’ was more realistic to define high BTVs that can better represent the so-called mineralized/normal background. Compared with CONAMA Resolution (No. 420/2009), the conservative BTVs of most of the toxic elements were below the prevention limits (PV), except Cu, but when the high BTVs are considered, Cu, Co, Cr and Ni exceeded the PV limits. The degree of contamination (Cdeg), based on the conservative BTVs, indicates low contamination, except in the Carajás basin, which shows many anomalies and had high contamination mainly from Cu, Cr and Ni, but this is similar between surface and deep soils indicating that the observed high anomalies are strictly related to geogenic control. This is supported when the Cdeg is calculated using the high BTVs, which indicates low contamination. This suggests that the use of only conservative BTVs for the entire region might overestimate the significance of anthropogenic contamination; thus, we suggest the use of high BTVs for effective assessment of soil contamination in this region. The methodology and results of this study may help developing strategies for geochemical mapping in other Carajás soils or in other Amazonian soils with similar characteristics.

  • Uptake of Cd, Pb, and Ni by Origanum syriacum produced in Lebanon 2019-08-06


    Trace metals are found naturally in soil. However, the increase in industrial and agricultural polluting activities has increased trace metal contamination and raised high concerns in the public health sector. The study was conducted on Origanum syriacum, one of the most consumed herbs in the Middle East, and was divided into three parts. (1) Pot experiment: to study the effect of Cd, Pb, or Ni levels in soil on their uptake by O. syriacum. (2) Field samples: collected from major agricultural regions in Lebanon to analyze Cd, Pb, and Ni concentrations in soil and leaves. (3) Sale outlets samples: to measure the levels of Cd, Pb, and Ni in O. syriacum tissues in the market. Results showed that there was a positive correlation between levels of Cd, Pb, and Ni in soil and those in O. syriacum tissues. None of the field samples contained Pb or Ni that exceeded the maximum allowable limits (MAL). Three samples collected from heavily poultry-manured soil contained Cd higher than the MAL. Samples collected from sale outlets did not exceed the MAL for Ni but two exceeded the MAL for Cd and one for Pb. Trace metal contamination is not a major concern in O. syriacum produced in Lebanon. Only one mixture sample from a sale outlet was higher in Pb than the MAL and three samples from heavily manured fields exceeded the MAL for Cd.