A lowered salt intake does not compromise iodine status in Cape Town, South Africa, where salt iodization is mandatory

Abstract

ObjectiveUniversal salt iodization is an effective strategy to optimize population-level iodine. At the same time as salt-lowering initiatives are encouraged globally, there is concern about compromised iodine intakes. This study investigated whether salt intakes at recommended levels resulted in a suboptimal iodine status in a country where salt is the vehicle for iodine fortification. MethodsThree 24-h urine samples were collected for the assessment of urinary sodium and one sample was taken for urinary iodine concentrations (UICs) in a convenience sample of 262 adult men and women in Cape Town, South Africa. Median UIC was compared across categories of sodium excretion equivalent to salt intakes lower than 5, 5 to 9, and greater than or equal to 9 g/d. ResultsThe median UIC was 120 μg/L (interquartile range 75.3–196.3), indicating iodine sufficiency. Less one-fourth (23.2%) of subjects had urinary sodium excretion values within the desirable range (salt <5 g/d), 50.7% had high values (5–9 g/d), and 22.8% had very high values (≥9 g/d). No association between urinary iodine and mean 3 × 24-h urinary sodium concentration was found (r = 0.087, P = 0.198) and UIC status did not differ according to urinary sodium categories (P = 0.804). ConclusionIn a country with mandatory universal salt iodization, consumers with salt intakes within the recommended range (<5 g/d) are iodine replete, and median UIC does not differ across categories of salt intake. This indicates that much of the dietary salt is provided from non-iodinated sources, presumably added to processed foods.