Assessment of knowledge and availability of iodine in table salt among households and street vendors in Nyamagana District, Mwanza, Tanzania

Abstract

Background: Iodine deficiency is a major public health problem and a leading cause of preventable cognitive impairment globally. It accounts for approximately 90% of goiter cases and 5–15% of cretinism in severely endemic areas. To address iodine deficiency disorders (IDD), Tanzania implemented Universal Salt Iodization (USI) in 1994. However, previous assessments indicated that household coverage of adequately iodized salt was below the World Health Organization (WHO) recommended level of ≥90%. Regular monitoring is recommended every three years. This study assessed knowledge of iodine and availability of iodized salt among households and street vendors in Nyamagana District, Mwanza, Tanzania.

Methods: A cross-sectional mixed-methods study was conducted. A total of 417 participants were included in the quantitative component and 30 in the qualitative component. Salt samples were tested for iodine content using MBI rapid test kits. Quantitative data were analyzed using descriptive statistics (means and percentages), while qualitative data were analyzed using thematic analysis.

Results: Of the 417 salt samples tested, 399 (95.7%) contained iodine, with 355 (85.0%) having adequate iodine levels (>15 ppm). All packed salt samples (342, 100%) contained iodine, compared to 45 (97.8%) of unpacked salt and 16 (55.2%) of crude salt. In total, 18 (4.3%) samples contained no iodine, all of which were crude salt. Despite the high availability of iodized salt, knowledge levels were limited. Although 265 (63.5%) participants had heard of iodine, only 217 (51.1%) correctly identified at least one function, and less than one-third (32.6%) could identify any dietary source. Awareness of vulnerable groups requiring higher iodine intake was low (8.9%), and only 6 (1.4%) participants reported checking salt labels to confirm iodization. Additionally, improper storage practices were common, with 98 (23.5%) storing salt in open containers, which was associated with lower iodine levels. Qualitative findings revealed widespread misconceptions about iodized salt, including beliefs that it contains harmful chemicals and that crude salt is superior.

Conclusion: High availability of iodized salt indicates substantial progress in USI implementation in Tanzania. However, gaps in public knowledge persist. Strengthening community education alongside continued monitoring and enforcement of iodization standards is essential to sustain achievement