Goitre, alternately spelled as goiter, is a non-cancerous enlargement of the thyroid gland. Iodine deficiency is the primary cause of goitre. The average daily requirement of this micronutrient for an adult is a mere 150 micrograms, an amount so small that it could fit on to a pinhead. Our normal requirement of this micronutrient comes from crops grown on iodine-rich soil. But when soil of any area lacks iodine, the crops grown on such soil too are deficient in this essential micronutrient.
Consequently, those people who live on iodine-deficient land and eat its crops regularly do not get their daily requirement of this essential element. In India, the prevalence of goitre, around 30 to 50 per cent, is reported from areas of iodine deficiency which lie in the great subHimalayan belt that extends from Jammu and Kashmir, all along North India, to West Bengal and North East India. Iodine is naturally present in soil, but it is easily leached away by rainfall and runoff in hilly and other goitre-prone areas leading to iodine deficiency in soil and water in these areas. Moreover, those areas also suffer from huge erosion of topsoil. As a result, locally grown crops and livestock often have low iodine levels, leading to dietary deficiency in the population.
Modern science recognises the distinct influences of soil health on human health. In August 2023, researchers from the US and Australia published their studies in the journal Scientific Reports, which for the first time conducted a large-scale evaluation of the relationship between the availability of micronutrients in the soil and nutritional status of people in India. Their findings hold clues for the country to not only improve soil health but also to address the longstanding challenge of malnutrition among children and women. Soil fertility refers to the inherent capacity of a soil to supply essential nutrient elements to the plants in adequate amounts and in the right proportion for their optimum growth. It is one of the key components to determine productivity. It is defined as the quality of a soil that enables it to provide essential chemical elements in adequate quantities and proportions for the growth of specific plants.
The essential nutrient elements comprise the key components of soil fertility vis-à-vis plant nutrition and therefore these are referred to as plant nutrients or nutrient elements. The living cells of plants have the capability to take up substances from the environment and use them for the synthesis of their own cellular components or as their energy source.
A large number of mineral elements are present in plants, but they do not require all these. Only some of them are essential and necessary for their growth and development, whereas others are taken up either incidentally or their essential role has yet to be established. Out of the 118 elements in the Periodic Table, 90 elements naturally occur in plants, out of which only 17 are essential nutrients. However, most of the 118 elements exist in the earth’s mantle, earth’s crust or soil but the magnitude of their concentration varies. Plants, being an active entity, absorb selectively some of these elements and discriminate or reject the others. Nevertheless, a plant’s composition reflects to a large extent the components of the soil that support it or vice versa.
The study report published in Scientific Reports reveals that researchers conducted a large scale evaluation in which they analysed over 27 million soil tests, drawn from a nation-wide government programme called Health Card, and health data of 0.3 million children and one million women from the National Family Health Survey (NFHS). The study focused on two key essential micronutrients (minerals) ~ Zinc (Zn) and Iron (Fe) ~ which play crucial roles in our body. Zn plays crucial roles in various bodily functions: immune system, wound healing, hormone regulation, protein synthesis and eye health. It also has antioxidant properties, protecting our cells from damage caused by free radicals. Iron is a critical component of hae mogl obin, carrying oxygen from the lungs to all parts of our body.
Moreover, it is required for energy production, the immune system, brain functions, and also for the prevention of anaemia. The researchers found that districts where soil zinc availability was significantly low had higher rates of stunting (low height for age) amongst children. Surprisingly, the Zn-stunting relationship was strong even in wealthier households. Growth stunting in childhood is a risk factor for increased mortality, poor cognitive and motor development, and other impairments in functions. The researchers also established a clear and close relationship between anaemia and Fe deficiency in soil. At places where the availability of soil nutrients, particularly Zn and Fe, was satisfactory, a positive correlation with the height and haemoglobin levels amongst children and women was established.
A one standard deviation increase in soil Zn (equivalent to 24.3 per cent increase in the proportion of Zn tests, as per their research paper) is associated with a reduction in stunting by 10.8 per 1000 children and with the reduction in underweight conditions by 11.7 per 1000 children. A one-standard deviation increase in soil-Zn is also associated with a 0.29 cm increase in a woman’s height. Likewise, a one-standard deviation increase in soil-Fe (equivalent to a 26.8 per cent increase in the proportion of Fe tests) is associated with 0.038 gram per decilitre increase in haemoglobin for children and 0.037 gram per decilitre in haemoglobin for women.
Micronutrient deficiencies are an important global health issue. They can result in poor physical and mental development in children, vulnerability or exacerbation of diseases, mental retardation, blindness, and general losses in productivity and potentiality. Unlike energy-protein undernutrition, the health impacts of micronutrient deficiency are not always visible. Micronutrient deficiency is therefore sometimes termed as ‘Hidden Hunger’. It is a phenomenon that occurs where crops are not getting optimal nutrition from soil or inputs, and even occurs without ever showing deficiency symptoms. Micronutrients include water soluble and fat soluble vitamins, macro-minerals (Calcium. Phosphorous, Magnesium, Sodium, Potassium and Sulphur) and micro-minerals (Zn, Fe, Copper, Molybdenum, Manganese, Chlorine and Boron). In the case of India, the findings of the researchers seem to be very significant.
According to UNICEF’s report, more than 80 per cent of adolescents in India suffer from hidden hunger (one in every two adolescents in India is deficient in at least two of the micronutrients our body needs). Though NHFS data shows a decline in child stunting between 2015-16 and 2019-21, the rate is still significantly high at 34 per cent among the children under five years of age. In 161 districts, more than 40 per cent under-five children suffer from stunting.
(The writer is a retired IAS office)