Salt Intake And Iodine Status In 12 Rural And Semi-Urban African Villages

INTRODUCTION: To assess the prevalence of iodine (I^-) deficiency and the relationship between salt and I^- intake in a community-based population study West Africa.

METHODS: 1,013 participants randomly selected from 12 villages (628 women, 481 rural) in Ashanti, Ghana. 997 (98.4%) had complete data for analysis (mean age [SD] 55 [11] yrs; BMI 21.1 [4.2] kg/m²). They were screened at baseline for anthropometry, blood pressure, provided a blood test and 2x24h urine collections. Urinary volume, sodium (Na⁺) and I^- were measured. Results are means [SD] or geometric means [95% CI].

RESULTS: Both daily urinary I^- (UIE: 81 [75, 87] v 48 [45, 52] µg/24h, p<0.001) and urinary I^- concentration (UIC: 111 [178] v 60 [71] µg/L, p<0.001) were higher in semi-urban than rural villages. Na⁺ did not differ (103 [45] v 99 [45] mmol/24h, p=0.23). Overall 35.1% had adequate I^- intake (UIC 100-199 µg/L). Rural participants had greater prevalence of I^- deficiency with two-fold higher prevalence of severe I^- deficiency (16.2 v 9.8%). In six villages there were significant direct relationships between Na⁺ and I^- excretion (concordant villages: r from 0.24 to 0.66), whilst in the remainder no significant associations were detected (discordant villages: r from 0.08 to 0.23), indicating that not all villages had direct access to, and consumption of, iodized salt. We estimate that, once adjusted for age, sex and locality, a 10 mmol difference in Na⁺ would be expected to be associated with 6.2 µg/24h difference in I^- in concordant villages and 1.1 µg/24h in discordant villages.

CONCLUSIONS: In Ashanti, salt intake is less than estimated by WHO. I^- intake is below recommended levels and only a third of the population has adequate I^- status. Variations in salt intake may affect I^- status moderately. This effect is likely due to level of access to iodized salt.