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 (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 LSHTM.
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.
 |
| Images from L-R: Fieldwork in Malawi; Cultivation and weeding are usually done by small-holder farmers using a hand-held hoe; Locally grown leafy green vegetables being sold at a market in northern Malawi. |
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.
 |
| Dietary supply of selenium in micrograms per adult male equivalent (AME) per day (d). |
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.
 |
| Images from L-R: Different types of fish provide a good source of micronutrients, here for sale at a market in Malawi; The clear colour difference betweel bulk soil samples collected over more acidic (red) soils, and calcareous (dark brown to black) vertisols. |
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 (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 LSHTM.
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