MRC policy briefs to government

Solving iodine deficiency in South Africa: so near - and yet so far

Dr Pieter Jooste

National Research Programme for Nutritional Intervention
Medical Research Council, PO Box 19070, Tygerberg 7505, South Africa.
Tel: (021) 938-0370; fax: (021) 938-0321; E-mail: pieter.jooste@mrc.ac.za

Iodine deficiency in communities not only causes endemic goitre, but results in a host of abnormalities collectively known as iodine-deficiency disorders (IDD). In severe iodine deficiency these disorders may include abortions, perinatal mortality, cretinism, hypothyroidism and mental retardation. Even moderate iodine deficiency poses a serious health threat in the form of endemic goitre, hypothyroidism and abnormalities in the psychoneuromotor and intellectual development of children1 and adults who have apparently normal thyroid glands.2 Indeed, iodine deficiency is the most common preventable cause of mental deficiency and brain damage in the world today.

Endemic goitre as a biological marker for iodine deficiency, as well as iodine deficiency itself, prevailed in many areas of South Africa in the past. Endemic goitre was reported for the first time in South Africa in 1927. Voluntary iodisation of table salt was introduced in 1954 at a level of 10 to 20 parts per million (ppm) to prevent and control the endemic goitre. However, because only about 30% of table salt was iodised and people had unequal access to iodised salt,3 significant prevalences of iodine deficiency and endemic goitre still existed in many parts of the country in the early 1990s.4,5

South Africa introduced compulsory iodisation of table salt at the end of 1995 to comply with one of the nutrition goals of the 1990 World Summit for Children that aimed to eradicate IDD by the year 2000. At the same time, the level of iodisation was increased to between 40 and 60 ppm.

In the following years the success of eliminating IDD in South Africa through compulsory iodisation of salt at an elevated iodine concentration was evaluated in a series of MRC studies and in a national IDD survey commissioned by the Department of Health.

Impact of compulsory iodisation
Compulsory iodisation of table salt, as a public health intervention to eliminate iodine deficiency, resulted in dramatic improvements in the short term in both the process (or intermediate) and the outcome (or impact) indicators of iodine deficiency and endemic goitre. Improvements in the process indicators were as follows:

Within 1 year the iodine content of table salt available in shops in three of the nine provinces more than doubled, from an average of 14 ppm to 33 ppm.6 This average further increased to 42 ppm over the next 2 years. However, 19,2% of the salt packages on retailers’ shelves still had an iodine content of less than 20 ppm.

In a national study on the iodine content of household salt, the MRC National Research Programme for Nutritional Intervention found that the coverage of iodised salt also improved remarkably, and the average and median iodine content of household salt appeared sufficient to eliminate IDD.7 On the positive side, the coverage of iodised salt improved from a situation before compulsory iodisation where only 30 % of table salt was iodised and unequal access to iodised salt existed, to a situation where 62% of households in the country were using adequately iodised salt of at least 15 ppm. Unfortunately, vulnerable groups in the population are still exposed to under- or non-iodised salt. These groups include people of the three northern provinces of the country, rural people, households using predominantly poorly iodised coarse salt, and low socio-economic households. A significant percentage, up to 20%, of households in some of these provinces use non-iodised agricultural salt in the preparation of their food. Therefore, the significant progress achieved in improving the coverage of adequately iodised salt is accompanied by factors and practices weakening the national iodisation programme.

Outcome indicators reflect the impact of the national salt iodisation programme on the iodine and goitre status of the population. Due to their vulnerability and accessibility, primary schoolchildren are used worldwide as a proxy group to assess IDD in the community. Evidence of improved outcome indicators in South Africa were:

The iodine status of primary schoolchildren of four communities in the Langkloof area in the southern Cape improved dramatically from before the introduction of compulsory iodisation at an elevated iodine concentration, to 1 year later, but the goitres in these children are taking longer to recover. 8

The South African Institute for Medical Research conducted a national IDD survey in 1998, commissioned by the Department of Health, which showed an adequate iodine status in most areas.9 This represents a major improvement in iodine status compared to the iodine deficiency and endemic goitre observed in several isolated studies in the early 1990s. However, evidence of IDD persisted in 16,2% of the schools in the survey, and the goitre rates still appeared to be high in virtually all the schools, requiring further investigation.

Policy implications
To strengthen this trend, a multi-pronged approach needs to be adopted to eliminate the barriers preventing the country from achieving a coverage of 90% of households using adequately iodised salt of at least 15 ppm. Important policy approaches should include the following:

• The salt suppliers must be seen as the primary role-player implementing the salt regulation. It is in their hands to increase the accuracy of salt iodisation and to reduce the variation observed in iodine concentration. To assist the producers in this role, effective liaison among the salt producers, the health authorities and scientists should be strengthened to enhance the mutual flow of information in a concerted effort to achieve the international goal of 90% adequately iodised salt.
• With the introduction of mandatory iodisation in South Africa, an important public health responsibility was placed on the shoulders of the salt producers. To meet the demands of this responsibility, a thorough understanding of the causes, consequences, prevention and control of IDD is required. Therefore, increasing the knowledge and awareness of producers regarding the prevention and control of IDD via the correct iodisation of salt may further strengthen their commitment towards the production of salt iodised according to the legal requirement.
• It is a standard recommendation that all countries that have implemented a national iodisation programme should also have a functional monitoring system in place. Regular monitoring of the iodine concentration at the production site, and at the retail and household levels, should be standard practice. Monitoring systems should include both process (e.g. the iodine concentration of salt, coverage of adequately iodised salt, etc.) and outcome indicators (e.g. urinary iodine, goitre rate) of IDD.
• One of the key issues that requires attention is the vulnerability of low socio-economic groups to under- or non-iodised salt. A particular focus needs be developed to ensure a sustainable supply of adequately iodised salt to the poorer sector of the population. It is of great importance that the salt produced for this segment of the market is adequately iodised, particularly in view of the general susceptibility of low socio-economic groups to iodine deficiency.
• Leakage of non-iodised agricultural salt to households occurred predominantly among people in the low socio-economic groups in the three northern provinces, presumably because it is a cheap source of salt to those who have access to it. Unfortunately, mandatory iodisation does not apply to agricultural salt used for animal nutrition and other agricultural purposes in South Africa. Therefore, a practical way to counteract the consequence of leakage, which deprives vulnerable people from consuming iodine-fortified salt, would be to iodise agricultural salt. This would also benefit animal production in iodine-deficient areas.
• At this stage it is uncertain whether the hot and humid summer climate of the three northern provinces plays a role in the lower iodine content of retailer and household salt found in those provinces. More research is needed to answer this question.

Conclusion
The success achieved in the national iodisation programme supports and strengthens the continuation of the fight against IDD in South Africa. The challenge in the new decade for producers and health officials is to eliminate factors precluding a coverage of 90% adequately iodised salt in the country, and to sustain the successes achieved until now.

References

1. Benadé JG, Oelofse A, Van Stuijvenberg ME, Jooste PL, Weight MJ, Benadé AJS. Endemic goitre in a rural community of KwaZulu-Natal. S Afr Med J 1997; 87: 310-313.
2. Delange F. The role of iodine in brain development. Proceedings of the Nutrition Society 2000 ; 59: 75-79.
3. Jooste PL, Marks AS, Van Erkom Schurink C. Factors influencing the availability of iodised salt in South Africa. S Afr J Food Sci Nutr 1995; 7: 49-52.
4. Jooste PL, Weight MJ, Kriek JA. Iodine deficiency and endemic goitre in the Langkloof area of South Africa. S Afr Med J 1997; 87: 1374-1379.
5. Kalk WJ, Paiker J, Van Arb MG, Pick W. Dietary iodine deficiency in South Africa. S Afr Med J 1998; 88: 357-358.
6. Jooste PL, Weight PL, Locatelli-Rossi L, Lombard CJ. Impact after 1 year of compulsory iodisation on the iodine content of table salt at the retailer level in South Africa. Int J Food Sci Nutr 1999; 50: 7-12.
7. Jooste PL, Weight MJ, Lombard CJ. A national survey of the iodine content of household salt. WHO Bull 2000 (in press).
8. Jooste PL, Weight MJ, Lombard CJ. Short-term effectiveness of mandatory iodization of table salt, at an elevated iodine concentration, on the iodine and goitre status of schoolchildren with endemic goitre. Am J Clin Nutr 2000;71:75-80.
9. Immelman R, Towindo T, Kalk WJ, Paiker J, Makuraj S, Naicker J, Omar S. Report of the South African Institute for Medical Research on the Iodine Deficiency Disorder Survey of Primary School Learners for the Department of Health, South Africa. South African Institute for Medical Research, 2000.