IODINE LEVELS IN EDIBLE SALT SOLD IN MALAWI, KENYA AND ZAMBIA

Kenji GM*¹, Nyirenda KK² and GC Kabwe³

ABSTRACT

Salt samples from some of the Kenyan, Malawian and Zambian markets were analysed for potassium iodate content by titrimetric method. The levels of potassium iodate for Kenyan salt samples ranged from 21.3±1.0 mg/kg to 142.8±2.8 mg/kg and were all below the minimum legal requirement of 168.5 mg/kg. This is in contrast to the declarations on the packets, which indicated that the salt was fortified with sufficient amount of potassium iodate as required by the law. There were variations also in iodine content in salt of the same brand sold in different parts of the country. Malindi at a low altitude and with a higher humidity than Thika had salts with lower iodate contents than Thika. On the other hand, 50 % of Malawian samples had levels within the recommended range of 80-100 mg/kg. Salt obtained from the supermarkets registered the highest concentrations (mean of 101.6 mg/kg) while that sold in the open markets by vendors contained an average of 68.1 mg/kg and the lowest levels (17.6 mg/kg) were obtained in salt supplied by small-scale salt producers. In Zambia, the imported salts sold in the open air-markets were below the minimum legal requirements (80-100 mg/kg) with a potassium iodate content range of 36 - 44 mg/kg. This suggests that there is a loss of potassium iodate due to environmental factors at retail level or the retailers were adulterating the iodised salt. All the locally produced salts analysed indicated a very high level of iodate content with a concentration range of 226-246 mg/kg which may suggest lack of proper quality control during the iodination process. The results showed differences between well-packed salt from supermarkets, unpacked salt sold by vendors and the salt that is traditionally produced by small-scale miners. This study reveals some weaknesses in the salt iodination programmes in these countries and recommends strict and periodic monitoring of the quality of the salts.

Key words: iodate, salt, Kenya, Malawi, Zambia.

French

TENEURS EN IODE DANS LE SEL COMESTIBLE VENDU AU MALAWI, AU KENYA ET EN ZAMBIE

RESUME
Des échantillons de sel pris de quelques marchés du Kenya, du Malawi et de Zambie ont été analysés pour déterminer la teneur en iodate de potassium par la méthode titrimétrique. Les teneurs en iodate de potassium dans les échantillons du sel kenyan variaient entre 21,3±1,0 mg/kg et 142,8±2,8 mg/kg et se trouvaient toutes au-dessous des conditions juridiques minimum de 168,5 mg/kg. Ceci est en contraste par rapport aux déclarations qui figuraient sur les paquets, qui indiquaient que le sel était fortifié avec la quantité suffisante d’iodate de potassium exigée par la loi. Il y avait également des variations dans la teneur en iode dans le sel de même marque vendu dans les différentes régions du pays. Malindi qui est à une basse altitude et qui a une plus grande humidité que Thika avait des sels contenant moins d’iodate que Thika. Par ailleurs, 50 % des échantillons du Malawi avaient des niveaux qui se situaient dans la gamme recommandée de 80-100 mg/kg. Le sel obtenu des supermarchés a enregistré les plus hautes concentrations (une moyenne de 101,6 mg/kg) tandis que le sel vendu par des marchands dans les marchés à ciel ouvert avaient une moyenne de 68,1 mg/kg et les niveaux les plus bas (17,6 mg/kg) ont été obtenus dans le sel fourni par des producteurs de sel de petite envergure. En Zambie, le sels importés vendus dans les marchés à ciel ouvert étaient au-dessous des conditions juridiques minimum (80-100 mg/kg) avec une teneur en iodate de potassium variant entre 36 et 44 mg/kg. Ceci suggère qu’il y a une perte d’iodate de potassium suite à des facteurs liés à l’environnement au niveau de la vente en détail, ou alors les détaillants ont falsifié le sel iodé. Tous les sels produits localement qui ont été analysés ont indiqué une très grande teneur en iodate avec une gamme de concentration de 226-246 mg/kg qui peut suggérer un manque de contrôle de qualité adéquat au cours du processus d’iodation. Les résultats ont montré des différences entre le sel bien emballé vendu dans les supermarchés, le sel non emballé vendu par des marchands et le sel qui est traditionnellement produit par des mineurs de petite envergure. Cette étude révèle quelques faiblesses dans les programmes d’iodation du sel dans ces pays et elle recommande un suivi strict périodique de la qualité des sels.

Mots-clés: iodate, sel, Kenya, Malawi, Zambie.

INTRODUCTION

The negative health and socio-economic impacts of iodine deficiency among the world population have been widely documented [1]. Apart from goitre and its associated psychological suffering in the patients, lack of iodine has been implicated to contribute significantly to high propensity to abortion, miscarriage and stillbirths in the affected pregnant women. Infants born from these women suffer severe intra-uterine skeletal and neurological growth retardation. Iodine deficient adults are less energetic, hence their work output and economic productivity is lower and can lead to chronic household food insecurity, poverty and malnutrition.

The prevalence of iodine deficiency disorders (IDDs) in most African countries ranges from mild in low-lying areas to severe in highlands [2]. Kenya, Malawi and Zambia are grouped among the 50 countries world-wide believed to have an iodine-deficiency disorder problem of public health significance.

In Malawi, a study conducted in 1995 in the central region of the country showed that about 50% of the pregnant women who had visited government hospitals that year were iodine deficient. Dwarfism, physical deformities, neurological damage, partial paralysis and lower Intelligent Quotient (IQ) among children born to these mothers were observed [3].

In Kenya, goitre has been recognised as a public health problem as early as 1926 [4]. A study done in Embu found a prevalence of 16% of goitre among pregnant women and teenage girls [5]. A National Council on Iodide Deficiency Disorders (NCIDD) has been formed and is actively co-ordinating all iodine efficiency disorders (IDDs) aspects in the country. Estimates based on urinary iodine excretion indicated that 62% of the population in Kenya was at risk of IDDs [6].

Zambia produces coarse salt from Kasempa and Kaputa. However, this production is not enough to meet her salt requirements. Zambia therefore imports most of her salts from neighbouring countries. We can therefore assume that Zambia can achieve universal salt iodination through regulation.

The use of iodised edible salt to reduce the risks associated with iodine deficiency has been incorporated in many nutrition programmes and legislation worldwide. Globally, 68% of households in countries with iodine deficiency disorders now consume iodised salt [7]. Despite these efforts by governments and international agencies to ensure that, communities consume only salt with sufficient amounts of iodine, there are many challenges in salt iodination programs.

The major drawback in the salt regulations in Africa is that the ability to enforce them is low and the monitoring and verification mechanisms are weak [8]. Compliance with the regulations in these countries has depended more on advocacy and potential for legal action than on enforcement.

The laws of Kenya, Malawi and Zambia stipulate that salt sold in the markets should contain <168.5, 80-100 and 50-84 mg potassium iodate per kilogram of salt, respectively. Yet, IDDs continue to record high prevalence in the sub-region without any significant hope of amelioration [7].

The objective of this study was to analyse the content of potassium iodate in edible salt sold in selected markets in Malawi, Zambia and Kenya and determine whether the levels meet national standards.

MATERIALS AND METHODS

Sampling procedure
Salt samples were bought from different market outlets in Kenya, Malawi and Zambia as follows:

Chemical analysis
The amount of potassium iodate in the samples was determined by titrimetric method according to Association of the Official Analytical Chemists [9].

RESULTS

Salts sold in Kenyan markets
All the Kenyan salt brands were well packed in plastic bags and the labels clearly declared that the salt was iodised. Table 1 shows that the levels of iodine in Kenyan salts ranged from 21 mg/kg to 143 mg/kg. The results also show a striking difference in the iodine concentration between samples collected from Thika and those from Malindi market. The potassium iodate concentration ranged from 40.2 to 142.8 mg and 21.3 to 42.5 KIO³/kg for Thika and Malindi markets, respectively.

Salts sold in Malawian markets
The results obtained in this study show that of the 12 samples collected from Malawian markets, 50% had potassium iodate levels within the recommended range of 80-100 mg/kg, while the lest had levels below the minimum recommended limit of 80 mg/kg (Table 1). Salt obtained from the supermarkets registered the highest concentrations (mean of 101.6 mg/kg) while that sold in the open markets by vendors contained an average of 68.1 mg/kg and the lowest levels (17.6 mg/kg) were obtained in salt supplied by small-scale salt producers.

Salts sold in Zambian markets
Most of the salt sold in Zambian markets is imported. Some of the imported salt is sold in the open-air markets and some is sold in supermarkets. The labels on the imported salts clearly indicated that they were iodised while the labels on the locally produced salts sold in the open-air markets did not indicate whether they were iodised or not. The potassium iodate content in the salts was found to vary between imported products and locally produced products (Table 2).

DISCUSSION

It was noted that all salt samples from the two outlets in Kenya were below the stipulated required standards of 168.5 mg/kg. This is in contrast to the declarations on the packets, which indicated that the salt was fortified with sufficient amount of potassium iodate as required by the law. There were variations also in iodine content in salt of the same brand and sold in different parts of the country. For example, three samples of the same brand were analysed for iodine content in Kenyan salt: one from Thika and two samples from Malindi. The results obtained were 142.6 mg/kg, 21.3 mg/kg and 29.4 mg/kg respectively. The differences observed might be attributed to different environmental factors that may enhance the degradation and loss of iodine from salt. All the salts from Kenya that were analysed were packaged in plastic bags and were of the white crystal type.

White crystal salt has been found to lose iodine at a faster rate than powdered or brown crystal salt [10]. The iodine loss in iodised salt is also greater for salt stored at a temperature of 37 ºC and humidities of 76% than in that stored at 20-25 ºC [11]. The former conditions are prevalent in Malindi and the later are prevalent in Thika. This would suggest that the consumers in Malindi are at more risk to iodine deficiency disorders (IDDs) than their Thika counterparts. However, it should be noted that human beings could take iodine from other sources like seafood [1] and increase the amount of iodine in the body thereby reducing the adverse health effects. Contrary to earlier findings that in Kenya 98% of salt is iodated [8], the results from this study reveal that none of the samples from Kenyan markets conformed to the required levels. A similar study in 1990/91 indicated that only 15.9% of Kenyan salt complied with legislation [12].

Most of the salt in Malawian markets is imported in bulk from Botswana. Vendors buy this salt from wholesalers and unpack it before selling to consumers. The unpacked salt is sold in open-air markets and is exposed to direct sunlight and air. All the salt is packaged in plastic bags and the labels clearly indicate that the salt is iodized. However, in Chikawa market, small-scale salt producers mainly supply the salt sold. The salt is produced from saline soils and does not undergo iodination process.

The high potassium iodate contents in salt from supermarkets clearly show that the brand of salt imported from Botswana contains iodine at higher levels than the maximum threshold. It is probable that the manufacturers deliberately put in excess iodate to compensate for the loss due to storage. Excessive intake of iodine causes thyrotoxicosis in human beings [8]. A study conducted in Zambia and the Republic of Congo revealed that hyperthyroidism occurred only when the introduction of iodized salt had been of recent onset [13]. This was attributed to the excess exposure to iodine due to mostly a poor monitoring of the quality of iodized salt. The risk of hyperthyroidism was also reported in Abidjan after the introduction of iodized salt [14]. A low level of iodate content was observed in salt sold in the open market despite having the same source. The average amount of potassium iodate in salt from the open market was slightly lower than that obtained from the supermarkets. The reduction may be attributed to the degradation of potassium iodate due to exposure to sunlight and air. The wide variation of iodine levels in samples from the open-air markets seem to suggest that the duration of exposure and thermodynamics factors are critical to the rate of loss of iodine in salt. It is, therefore, imperative to understand the dynamics and mechanisms of potassium iodate degradation. This information would be important in determining the shelflife and proper handling conditions of salt.

Low levels of iodine in salt from Chikwawa, where small-scale miners produce salt for sale should be a concern. The average potassium iodate content in these samples was more than four-fold lower than the minimum recommended levels. It is not unexpected to observe the presence of iodine even though the salt does not undergo iodization process. Iodine occurs naturally in the soil [1] and Chikwawa being a low-lying area, there is probably the accumulation of iodine in the saline soils that are used for producing salt. In this case, it is probable that the salt is not iodated at all.

In Zambia, all the imported samples from the supermarkets were within the Zambian legal requirements. The imported samples from the open air-markets were below the minimum legal requirements with a potassium iodate content range of 36 - 44 mg/kg. This suggests that there is a loss of potassium iodate due to environmental factors at retail level or the retailers were adulterating the iodised salt. All the locally produced salts analysed indicated a very high level of iodate content with a concentration range of 226-246 mg/kg. This may suggest lack of proper quality control during the iodination process.

CONCLUSIONS AND RECOMMENDATIONS

The findings from this study reveal some weaknesses in the salt iodination programmes in Africa despite some substantial successes registered by such programmes. In salt from Kenya, all samples were below the recommended limit while in Malawian salt 50% of the samples conformed to the required range. The imported salt in Zambian supermarkets was within the legal requirement. However, substantial loss of iodate occurs at the open air-markets. The locally produced salt in Zambia contains alarmingly high levels of potassium iodate, which could result in hyperthyroidism. This study indicates that despite the existence of regulations, the dangers of IDDs still persist in these countries. This therefore calls for strict and periodic monitoring by the regulatory bodies to make salt producers adhere to the set national standards. Monitoring should be at the factory level as well as the retail level. Monitoring for compliance is very important, since excessive levels could cause thyrotoxicosis and inadequate levels would be ineffective. When monitoring mechanisms are well established, these countries would need to evaluate and verify the impact of the iodination programmes. More work is also needed to determine the dynamics and factors that affect the loss of potassium iodate in salt.

ACKNOWLEDGEMENTS
The authors would like to thank JICA for financial assistance and members of staff of JKUAT for logistical, technical and moral support that enabled us to carry out this project successfully. We also wish to thank Malawi Industrial Research and Technology Development Centre and Food and Drugs Control Laboratory, Zambia for their support..

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*Corresponding author - Email: fsptjku@arcc.or.ke
¹ Department of Food Science and Technology, Jomo Kenyatta University of Agriculture and Technology, P.O. Box 62000, Nairobi, Kenya
² Malawi Industrial Research and Technology Development Centre, P.O. box 357, Blantyre, Malawi
³ Food and Drugs Control Laboratory, P.O. Box 3018, Lusaka, Zambia