Iodine fortification of salt increases children’s numeracy and literacy skills by up to 6%, strengthening the argument for Universal Salt Iodization (USI) according to researchers at the University of Sussex.

The study, presented at the Royal Economic Society annual conference in Brighton today by researcher Wiktoria Tafesse, analyzed the impact of a recent mandatory salt iodization policy implementation in India on literacy and numeracy scores of children in rural India.

Medical research shows strong associations between iodine deficiency in utero and early postnatal life and permanently low IQ, and the research suggests that the positive effects of fortification carry into childhood and beyond.

The causal impact of salt iodization was analyzed by comparing the trajectories in attainment of those children who experienced salt iodization in early life to those who were too old to benefit from the new Indian iodization policy, across districts with and without a geographical predisposition to iodine deficiency.

The data revealed that being exposed to the policy in early life improved the likelihood of recognizing simple letters and numbers by up to 6%.

As the children were tested in the home, the changes can’t be attributed to any changes in school policy or attendance, and shows that the results were not driven by coincidental improvements in health or access to school.

The study also found that there is a gender difference on the impact of iodine fortification, with improvements seen in girls’ overall reading score but no change of effect found for boys.

The UK has been identified as a country with mild-to-moderate iodine deficiency in pregnant women. Adequate iodine intake among pregnant women is critical for the brain development of the fetus and thus permanent cognitive attainment of the next generation.

Over 140 countries have implemented USI across the globe so far, but the UK has not adopted legislation on salt iodization despite USI being viewed as a simple and cost-effective way to increase iodine levels in the general population.

The reasoning for this in the UK may be that such a policy would conflict with current public health advice, encouraging lower salt consumption. However, WHO policy states that iodization and salt reduction can happen in tandem.

Discussing her research, Wiktoria Tafesse said:

“2 billion people worldwide are at risk for iodine deficiency, caused by low iodine content in soil and groundwater and dietary differences.”

“These findings are relevant to public policy issues in countries across the world, and suggest that the implementation of USI in countries with iodine deficiency would be a positive step.”

“Mandating and enforcing USI in developing countries could also constitute a very low cost policy to improve human capital throughout the life course, especially in many Sub-Saharan African countries with a very low consumption of iodized salt.”

Though school enrollment and school attainment has risen in many parts of the developing world, learning outcomes have remained poor in many countries.

Estimates from this new research suggests that increasing the national coverage of iodized salt from 10% to 90% could increase the proportion of children attaining basic academic skills by at least 10%.