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

The study, to be presented at the Royal Economic Society''s annual conference at the University of Sussex in March 2018 by researcher Wiktoria Tafesse, analyses the impact of a recent mandatory salt iodisation 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 iodisation was analysed by comparing the trajectories in attainment of those children who experienced salt iodisation in early life to those who were too old to benefit from the new Indian iodisation policy, across districts with and without a geographical predisposition to iodine deficiency.

The data reveal that being exposed to the policy in early life improves the likelihood of recognising 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 finds 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 and Russia are the only high-income countries ranking among the 10 most iodine-deficient nations in the world.

Over 140 countries have implemented USI across the globe so far, but the UK has not adopted legislation on iodine requirements 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 is that such a policy would conflict with current public health advice, encouraging lower salt consumption.

Discussing her research, Wiktoria Tafesse says:

''Two billion people worldwide are at risk for iodine deficiency, caused by low iodine content in soil and groundwater and differences in diets.''

''Most countries battling iodine deficiency today are low income countries but the UK is one of two high-income countries that rank among the ten most iodine-deficient nations in the world.''

''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 such as the UK 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 iodised salt.''

Though school enrolment 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 suggest that increasing the national coverage of iodised salt from 10% to 90% could increase the proportion of children attaining basic academic skills by at least 10%.

Notes for editors:

The UK is one of seven out of 29 European countries which do not have legislation on iodine requirements. (Iodine deficiency in Europe: a continuing public health problem. WHO and Unicef 2007, Edited by Maria Andersson).

The UK is ranked number 7 among the countries with the largest burden of iodine deficiency. Russia is the only other high income country among the 10 most iodine deficiency countries in the world, the other 7 are African nations and Afghanistan (Global Iodine Status in 2011 and Trends over the Past Decade, 2012, Maria Andersson, Journal of Nutrition).

Even though the policy recommendations in The effect of mandatory iodine fortification on cognitive test scores in rural India by W. Tafesse are mainly directed at low income countries which have a higher rate of other forms of malnutrition compared to high income countries, the findings should be of relevance for UK policy as well. Many British scholars have been advocating USI in the UK for a long time: http://www.thelancet.com/pdfs/journals/landia/PIIS2213-8587(16)30055-9.pdf

Despite the fact that probably around two thirds of the pregnant women in the UK are iodine deficient, a recent government scoping paper from the standing advisory commission on nutrition has not recommended iodine supplementation in pregnancy and even still questions the methodology of the iodine status assessment in populations. There is a requirement for a national large-scale survey of iodine supply in pregnant women in the UK to confirm the initial findings from relatively small samples. (Iodine Status in Europe in 2014, Lazarus, 2014 Eur Thyroid J. 2014).