Our analyses of different soil types and diets suggests that selenium deficiency is likely to be prevalent amongst the vast majority of Malawi’s population. We must now conduct a cost-benefit analysis of selenium-enriched fertiliser use.
Dr Martin Broadley
The findings of an international study published in the journal Scientific Reports
suggest that the enrichment of crops via the addition of a naturally occurring soil element to fertilisers, could help to reduce rates of disease and premature death in Malawi. Whilst the scientists have stated that more research needs to be conducted before policymakers commit to a particular approach, they also believe that action is likely to be necessary in order to address the dietary deficiency of the mineral selenium; a problem thought to be endemic amongst the Malawian population.
Selenium plays an important role in supporting human immunity. Individuals whose diets include low levels of selenium are at higher risk of suffering from certain diseases than those who receive sufficient quantities of the mineral. The scientists claim that the problem of selenium deficiency should be considered within the context of wider mineral malnutrition. Similar dietary shortfalls of iron, zinc and iodine are believed to exist across Southern Africa; a problem that is sometimes referred to as the ‘hidden hunger’.
The study was headed by academics at the University of Nottingham
, and was primarily funded by the Natural Environment Research Council (NERC)
, the Department for International Development (DFID)
and the Economic and Social Research Council (ESRC)
under the Ecosystems Services for Poverty Alleviation (ESPA)
scheme. During the course of their investigation, the researchers discovered that most Malawian soils were incapable of providing enough selenium for adequate human nutrition. In light of this, the team is calling for further research to determine the costs and benefits of using selenium-enriched fertilisers to boost levels of the mineral within the nation’s food.
To learn more about the dietary dearth of selenium uncovered by the investigation, and to find out what measures might help to address the problem, I spoke to study leader Dr Martin Broadley from the University of Nottingham’s School of Biosciences
. I began by asking about the most significant dangers associated with a deficiency of this particular mineral.
"When it comes to selenium deficiency, the main problem is decreased immune functioning," Dr Broadley replied. "The epidemiological evidence suggests that this deficiency is associated with a range of conditions, both communicable and non-communicable. Immune functioning is the key area of health affected by a deficiency in this mineral."
One of the major challenges commonly associated with the implementation of agricultural initiatives in developing countries is funding. Just because experts believe that a particular measure has the potential to benefit a country’s citizens, it doesn’t necessarily follow that money will be available to support that scheme. In light of this, I asked Dr Broadley whether the use of selenium-enriched fertilisers in Malawi would be economically feasible.
"The cost of selenium as a raw material is relatively trivial," he explained. "This isn’t an expensive element to buy. The most expensive component of selenium-enriched fertiliser is actually nitrogen. However, Malawi has a large subsidised fertiliser sector. The government invests significantly in fertiliser imports and distributes vouchers via its Ministry of Agriculture and Food Security
and extension workers. This provides small farmers with access to nitrogen fertilisers for their maize crops."
Dr Broadley and his colleagues studied the diets and resulting nutritional statuses of 120 18-to-50-year-old women living in the Mikalango and Zombwe regions. Research assistants from Lilongwe University of Agriculture and Natural Resources
and Malawi’s Ministry of Health
spent time in the homes of volunteers, and collected duplicate samples of what the women consumed during a 24-hour period. Blood and urine samples were then sent to UK scientists, who analysed their levels of selenium.
The researchers found that participants from the Zombwe region had significantly lower levels of selenium in their systems than those from Mikalango – less than half of the amount in their blood and approximately a third of the amount in their urine. In light of these geographical variations, I asked Dr Broadley whether or not he would favour a targeted approach to the use of selenium-enriched fertilisers.
"At present, we are simply calling for more research to be carried out," he replied. "We need to know the exact extent of the deficiency’s spread before deciding on the most appropriate course of action. Selenium should be brought into the fold with other micronutrients such as iron, zinc and iodine. Wider-scale assessments of deficiencies in these minerals have been conducted, and the same should be done for selenium. Our analyses of different soil types and diets suggests that selenium deficiency is likely to be prevalent amongst the vast majority of Malawi’s population. We must now conduct a cost-benefit analysis of selenium-enriched fertiliser use. The initial calculations suggest that the annual cost of the raw materials needed for this scheme would be around four US cents per capita."
Even if this approach is implemented in Malawi, it will not be the first instance of supplemented fertilisers being used to boost a population’s selenium levels. Finland has been using the strategy since the mid 1980s. I asked Dr Broadley about the extent to which the Finnish example might help his team to ascertain whether or not selenium-enriched fertilisers will benefit Malawi.
"There are several things that we have learned from the Finnish data," he explained. "For instance, we know that this approach increases all of the relevant biomarkers connected with a population’s selenium status. Moreover, it has been demonstrated that it is a stable technology; there are no risks associated with environmental damage or pollution. Unfortunately, the example cannot inform us of the explicit benefits brought about by higher selenium levels. This is because randomised controlled trials were never conducted in Finland. It simply isn’t possible, therefore, to devise an economic cost-benefit analysis from the Finnish study. Even so, we do know that the scheme has succeeded in providing adequate levels of selenium to the country’s population."
Whilst the research of Dr Broadley and his collaborators has been focused on Malawi, the hidden hunger of mineral deficiency is thought to exist across other African regions. I asked whether or not selenium-enriched fertilisers have the potential to benefit any of Malawi’s African neighbours.
"Supplemented fertilisers could help in this respect, but it is important to stress that selenium deficiency is not a problem exclusive to the African continent," said Dr Broadley. "Most UK soils, for example, do not supply adequate levels of selenium. The Malawian project was actually built on the back of research that we conducted in the UK in the mid 2000s. Even so, this approach certainly has the potential
to benefit other regions. Our paper includes a food-balance chart that illustrates dietary selenium availability on a per capita basis. Based on what different food and agriculture organisations are saying about what citizens are eating, we think that similar deficiencies exist across much of Central and Southern Africa.
"Of course, this is broad-brush approach," he continued. "It is not an accurate account of what each person is eating. However, it does serve to highlight a significant problem in terms of mineral deficiency; probably in the region of 20 to 25 per cent across the continent. In some countries, this figure is likely to be as high as 80 per cent."
Finally, I asked Dr Broadley how he would like the project to progress. What are the next steps for the researchers, and is sufficient funding available for the continuation of the study?
"Unfortunately, we have only ever had access to relatively small amounts of funding," he explained. "This is a project that has survived because of students’ goodwill and lots of collaboration. We did receive £50,000 from the ESPA scheme to bring a consortium of people together. We now have a PhD student based in sub-Saharan Africa, and we’ve submitted project applications to the Royal Society
for the continuation of our work. At one level, we would like to improve our understanding of soil maps. However, we would also like to explore the relationship between soil quality and the mineral statuses of local populations. If we can enhance the resolution of our understanding in these areas, we can test whether or not our predictions are valid.
"We are currently trying to secure funding for the next phase of our research," concluded Dr Broadley. "We need to conduct randomised controlled trials with enriched and non-enriched maize. These trials would provide the basis for a cost-benefit analysis concerning the use of supplemented fertilisers to introduce selenium and other micronutrients into the diets of Malawian citizens."
Dr Broadley and his colleagues at the University of Nottingham conducted their research in collaboration with academics from the University of East Anglia, Lilongwe University of Agriculture and Natural Resources, the British Geological Survey, the University of Otago, the International Food Policy Research Institute and Malawi’s Ministry of Agriculture and Food Security and Ministry of Health.