Salt-restriction and adequate iodine consumption: Dual burden or twin-opportunity?

Iodine deficiency disorders (IDD) have been identified as one of the top micronutrient deficiencies. India’s National Iodine Deficiency Disorder (IDD) Control Programme has been successful in achieving the optimal median urinary iodine concentration (mUIC) in the population at the national and zonal levels.^[1]

The epidemiological transition ratio ranges from 0.16 to 0.74, across the states of India,^[2] which signifies the shift in pattern from communicable to non-communicable diseases (NCDs). With the launch of the National Programme for Prevention and Control of Cancer, Diabetes, Cardiovascular Diseases and Stroke (NPCDCS), a comprehensive initiative to control NCDs has been taken by India. India is at a turning point where the iodine adequacy must be interpreted in the background of the global target of 30% relative reduction in mean population intake of salt/sodium by 2025,^[3] the major vehicle of iodine in India.

Paradox or two sides of the same coin?

High salt intake has been associated with increased risk of cardiovascular diseases (CVDs).^[3],[4] At the same time, salt has been universally accepted and promoted as a vehicle for iodine delivery to the masses in many countries including India.^[5],[6] The iodization level of 20-40 mg/kg in salt at production, the standards prescribed worldwide, is based on an average salt intake of 10 g/day at the population level, which may have changed. The Food Safety and Standards Authority of India (FSSAI) mandates an iodine concentration of >15 ppm in salt at the distribution level. The mUIC of the Indian population was found to be optimal in the range of 128.6-204.0 μg/L, with an average salt intake of 11. 9 g/day.^[1] However, when we work towards honouring our commitments in the global targets for the prevention and control of NCDs, which will be a major boost for tackling the emerging burden of NCDs in India,^[2] 30% reduction of salt consumption will reduce salt intake to 8.3 g/day, by 2025. The above shift will cause a decrease in the iodine intake through salt, and iodine deficiency.^[7] Hence, we face two paradoxical problems—salt-restriction and iodine-adequacy that might have contradictory solutions. However, they need not necessarily be contradicting. The objectives of iodine adequacy and salt restrictions are compatible and can coexist.^[6]

The twain shall meet: Paradigm shift

At the national level, close collaboration between the salt-iodization and salt-reduction programmes is required so that their aims are congruent and not contradictory.^[8] Integration at all possible levels and pooling in resources from various programmes involved in IDD control, NCD prevention and maternal health, can be worked out.^[6] Iodine concentration in salt during fortification can be titrated according to the levels of salt intake and mUIC of the population.^[6]

Policy-making

Achieving the goal of salt reduction and IDD elimination will require bringing together a multidisciplinary team of experts in health and other fields including public health (treatment and prevention), law, advertising, behavioural psychology, economics, behavioural economics, commerce and trade and political science.^[6] Policies on food industries must include the mandatory use of adequately iodized and a reduced, uniform quantity of salt in processed food across the country.^[5],[6]

Communication and advocacy

Potentially conflicting messages from the health sector, for example, ‘eat salt to ensure you get adequate intake of iodine’; ‘reduce salt to prevent CVDs’, must be avoided. Better, apt, common and crisp messages, imbibing both salt restriction and iodine adequacy, such as ‘Low but iodized salt’, ‘Little salt, but all iodized’ in multiple languages must be created and disseminated at the consumer level.^[6] Under ‘The Eat Right’ Movement, the Food Safety and Standards Authority of India (FSSAI) has asked food manufacturers to voluntarily reduce the content of salt in products and implement mandatory labelling of contents on food packets.^[9]

Monitoring and surveillance

The data available from the current monitoring and assessment surveys of IDDs and its programme are neither representative nor in line with the guidelines of WHO.^[10] Community level iodine surveys can be incorporated as a part of surveys such as the National Family Health Survey, to be nationally representative and economically viable. Pregnant women’s mUIC and urine sodium levels can be evaluated by utilizing the ANC clinics at the primary health centres (PHCs) and tertiary care hospitals.

The proportion of iodine in the diet contributed by various sources other than salt, becomes relevant as the mUIC has been found to be adequate even among households consuming non-iodized salt.^[1] Hence, monitoring of iodine intake from sources other than salt must be done.^[11] The association between reduced salt intake, adequately iodized salt and mUIC must be researched further, as studies and surveys have shown that even with restricted levels of salt intake, i.e. <5 g/day, and inadequately iodized salt consumption, subjects were iodine sufficient.^[1],[7],[11]

Alternative vehicles for iodine fortification and special groups

It is important to recognize specific population groups (e.g. pregnant women and lactating women) require higher iodine intake than others and hence may need to be targeted in other ways for the adequate consumption of iodine such as potassium iodide tablets and iodized oil. In addition to strengthening the salt iodization programme, it is essential to look for additional vehicles and modalities to deliver iodine.

Conclusion

Salt-restriction is feasible and can be effective in combination with salt-iodization. The initiatives on control of NCDs, which will occupy the centre-stage in India in the coming days, should tag along the compatible and vital public health campaign of IDD control. The integration of the strategies must be prioritized to reap the twin benefits in IDD and NCD control.

Conflicts of interest. None declared