|
|
Iodated salt -solving the most common preventable cause of mental deficiency in
the world.
Human beings require iodine for the production of the thyroid hormones, thyroxine and triiodothyronine. Insufficient production of these hormones, due to even moderate iodine deficiency affects the development and functioning of various systems of the body, with the most pronounced effect on the brain. The disorders resulting from iodine deficiency are called the iodine deficiency disorders (IDD) which manifest in the form of mental retardation, enlarged thyroid (goitre), increased childhood mortality, hypothyroidism, and reproductive failure. Damage to the brain may result in children lacking the ability to learn at school and in adults to work effectively. Impaired intellectual development may eventually lead to economic stagnation as one of the serious threats posed by iodine deficiency.
World-wide the two most important indicators of iodine deficiency in communities are the concentration of iodine in the urine and the prevalence of goitre. The goitre is used as a biological marker for iodine deficiency. As early as 1927, endemic goitre was reported in South Africa and is a direct result of iodine deficiency. Insufficient production of thyroid hormones stimulates the pituitary gland release of more thyroid-stimulating hormone, which in turn leads to the enlargement of the thyroid. The resulting goitre is an easy marker for iodine deficiency used by health care workers in programmes assessing the prevalence of deficiencies. The concentration of iodine in urine samples is measured in the laboratory.
Iodine is found in the soil and makes its way to humans and livestock through food grown in these areas. Unfortunately, the iodine is not distributed evenly across the Earth's crust. According to the WHO at least 29% of the world's population live in areas of iodine deficient soils. These include mountainous regions, areas prone to flooding and those subject to soil erosion and deforestation. The oceans contain adequate iodine and those eating seafood are less likely to suffer from IDD, however, in some coastal communities this does not necessarily hold true.
Access to sufficient iodine remains a problem. It is viewed as the most common preventable cause of mental deficiency and brain damage in the world today. The iodisation of table salt has been introduced world-wide in an effort to eradicate
IDD. Since 1995 in South Africa, the compulsory iodisation of salt has brought about some dramatic improvements.
Before compulsory iodisation of table salt, only about 30% of table salt was iodised. Within 2.5 years after the introduction of compulsory iodisation at an elevated iodine concentration, at least 62 % of households were using adequately iodised salt. What about the rest? There are several vulnerable groups in society who are still exposed to under or non-iodised salt. These groups include rural populations, households using poorly iodised coarse salt or agricultural salt (it is not compulsory for agricultural salt to be iodised) and low socio-economic households. In certain groups, up to 20% of households use non-iodised agricultural salt in the preparation of their food. So, while dramatic improvements are being seen compared to the early 1990's certain practices are undermining the success of the national iodisation programme.
Due to their vulnerability and accessibility, schoolchildren world-wide are used as proxy groups to assess
IDD. Programmes assessing the iodine status of school-children in certain areas has shown a significant improvement with introduction of the compulsory iodisation if table salt. However, evidence of IDD and goitre rates persisted in 16,2% of schools surveyed.
The Medical Research council believes that a multi-pronged approach needs to be adopted to strengthen the positive trend in order to achieve a situation where at least 90% of all households use adequately iodised salt containing at least 15ppm of iodine.
Shouldering much of the responsibility are salt producers. Scientists believe that effective communication of the problems posed by IDD to salt producers and improved liaisons will strengthen commitment to production of iodised salt according to the legal requirement. Agricultural salt leakage to low socio-economic groups most susceptible to iodine deficiency, may also be solved by simply making it mandatory for all agricultural salt to be iodised.
Reaching the target to eliminate IDD requires efficient monitoring of the iodine content of salt at the production site, at retail level, and in homes. In addition, it is also important to evaluate the impact of salt iodisation on indicators such as the iodine status and the goitre prevalence in primary schoolchildren. Dr Pieter Jooste of the Medical Research Council has implemented methods for the routine analysis of iodine in urine.
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 salt 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.
This article is based on the MRC policy brief published in MRC News "Solving iodine deficiency in South Africa", by Dr Pieter Jooste of the Nutritional Intervention Research Unit of the Medical Research Council.
|
