Use of iodised salt in cheese manufacturing to improve iodine status of population in the UK

Iodine is an essential trace mineral. Iodine deficiency during pregnancy can lead to adverse postnatal consequences such as impaired mental development, reduced intelligence scores and impaired motor skills in the offspring of the deficient women (Khazan et al., 2013, Rayman et al, 2008). There is growing evidence in the UK of low dietary iodine intakes and potential iodine deficiency in vulnerable populations (pregnant women and women of child bearing age group) (Rayman and Bath, 2015, Vanderpump et al., 2011) and a paucity of information on the iodine content of food products. In developing countries where iodine deficiency is widespread, salt has successfully been used as a vehicle for iodine fortification, however iodised salt is not widely available in UK supermarkets and there are valid health concerns about promoting salt intake. Salt is an essential component of the cheese production process, and cheese is commonly consumed in the UK. The overall aim of the present study was to explore the use of iodised salt in cheese production to improve the iodine status in the UK. In order to accomplish this, 4 smaller interconnected aims were identified namely development of method and subsequent analysis of iodine content of cheese samples in the UK, examining these results in relation to the legislative policies regarding iodine fortification practised in the country of production of cheese, understanding about the knowledge, attitudes and practices of consumers regarding iodine nutrition and fortification through a survey and then finally manufacturing popularly consumed cheese varieties (soft cheese and cheddar – from the consumer survey) using iodised salt and comparing it with cheese made with non- fortified regular table salt in terms of iodine content and overall sensory acceptability. A cheese mapping exercise was conducted to gain an overview of cheese varieties available across three major supermarkets in the UK and their country of origin. Selected varieties of cheese were analysed for their iodine content which was subsequently mapped against legislation policies (mandatory or voluntary) for iodine fortification in their country of origin. A questionnaire was designed to explore the knowledge attitude and practices (KAP) of general consumers about the use of iodised salt in food products. After pilot testing and minor modifications, the questionnaire was used to obtain KAP data from general consumers (n=506). To explore the use of iodised salt in cheese production, a collaboration between UCLan and Food technology centre (Anglesey) was established. Two varieties of cheese (cheddar cheese and soft cheese) with two variations (with and without iodised salt) were developed. Sensory acceptability was assessed by both expert (at Cardiff Metropolitan University) and non-expert consumer (at UCLan) panels. The newly developed cheese samples were analysed for their iodine content to evaluate their potential as a novel vehicle of improving dietary iodine intake. The iodine content of cheese samples from countries with mandatory legislation ranged from 0.16mg/kg for creamy Danish blue cheese (from Denmark) to 0.76mg/kg for Canadian cheddar. From countries with voluntary legislation, the range in iodine content was much broader, from 0.08 mg/kg (Swiss Le Gruyere) to 0.92 mg/kg (Farmhouse Cheddar). Analysis of milk and salt samples revealed that the iodine content of all the selected salt samples produced in the UK was negligible. Consumer KAP survey results revealed a general lack of awareness about significance of iodine for optimal health with only 11% participants aware that it is ‘Extremely important’ for maintaining optimal levels of iodine in the body and a high percentage of participants (81%) were not aware of any illness associated with iodine deficiency. 11% of consumers reported seeing brands of iodised salt in supermarkets, indicating low availability in the UK and most (62%) expressed a preference for non-iodised salt. The survey also revealed that 61% of respondents reported consuming cheese more than once a week and that Cheddar cheese was the most popular variety. The iodine content of the soft and hard cheese made with iodised salt was higher (0.92 mg/kg and 0.77mg/kg respectively) than those made with regular salt (0.76mg/kg and 0.48mg/kg respectively). Sensory evaluation of this cheese by sensory experts and general consumers revealed the use of iodised salt in place of regular salt had no significant impact on the main attributes (colour, appearance, taste, texture, odour and overall quality) or specific characteristics (sweetness, bitterness, aftertaste, creamy odour, saltiness) of the cheese (Chi Square test p>0.05). In conclusion, this research has revealed that on a global scale, mandatory iodine fortification policy may result in more consistency in the iodine content of cheese. In a sample of the UK population, there was a lack of awareness of the importance of iodine for human health. The research demonstrated that replacing non-iodised salt with iodised salt in the production of both soft and hard cheese increased the iodine content of the cheese by 21% and 60% respectively and had no detectable impact on the sensory attributes, thus is potentially a useful vehicle for iodine fortification in the UK.