‘Deficiency in micronutrients in soil linked to health of children and women’

Districts with an increased proportion of soil zinc samples had significantly lower rates of child stunting and underweight
Soil zinc availability was associated with women's height while soil iron availability was linked to anaemia in women. Photo: iStock
Soil zinc availability was associated with women's height while soil iron availability was linked to anaemia in women. Photo: iStock

There is a strong relationship between soil micronutrients and nutritional outcomes of people, with nutrient deficient soil contributing to nutritional deficiency in especially children and adult women, a new study has highlighted.

Districts with an increased proportion of soil zinc samples had significantly lower rates of child stunting and underweight, said the paper titled Soil micronutrients linked to human health in India, published in Nature journal on August 21, 2023. 

Soil zinc availability is also associated with an increase in the height of women, it said. The second set of results suggested a strong relationship between soil iron availability and anaemia among women and haemoglobin levels among children and women.

Soil and health data summary, mapping at a district level. Source: Nature journal

The findings hold significance for India in two contexts. First, over 35 per cent of the soil in the country was estimated to be deficient in zinc and about 11 per cent estimated to be deficient in iron. 

Secondly, in terms of nutrition deficiency in humans, India has roughly a third of the global population suffering from micronutrient deficiency, as per Global Nutrition report 2018. Iron deficiency is also the primary cause of anaemia in India. 

While the rate of child stunting was about 39 per cent, malnutrition was one of the leading risk factors for loss of Disability-Adjusted Life-Years in 2017, according to the Lancet’s Global Burden of Disease Study 1990-2017

For the current soil micronutrient deficiency study, the researchers from Stanford University and Ohio State University in the United States of America and Deakin University in Australia found that “a one standard deviation increase in satisfactory soil zinc is associated with a 0.29 cm increase in women’s heights.”

Human zinc deficiency is generally found to inhibit linear growth and the results of the study thus suggest that crops harvested in such soil did not have the zinc necessary for growth.

Similarly, “a one standard deviation increase in satisfactory soil zinc is associated with a reduction in stunting by 10.8 per 1000 children and a reduction in underweight by 11.7 per 1000 children.”

Even though there have been discussions about the relationship between soil zinc and human zinc status in India, this is the first large scale study examining the association between soil mineral availability and human nutritional status. 

For the study, the authors utilised data from 2017-2019 of over 27 million soil tests publicly available at the district level, conducted in recent years by the central government’s Soil Health Card scheme. Data on children’s and women’s health, as well as data for study controls, were drawn from India’s 2015-16 National Family Health Survey (NFHS). 

The findings were important from a public health perspective. India has one of the highest prevalence of anaemia  53.1 per cent of women (age 15-49 years) and 58.5 per cent of children under the age of five were anaemic. 

“Our results suggest that soil mineral availability is a potential channel that could be leveraged to mitigate the prevalence of anaemia across a large section of the population,” said the paper. 

However, the effect of association of low soil zinc availability with childhood stunting appeared  to be strongest in wealthier households. This the authors said, perhaps reflected the fact that children from poorer households face many more health constraints beyond zinc status that contribute to stunting.

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