Low-Salt Intake Suggestions in Hypertensive Patients Do not Jeopardize Urinary Iodine Excretion

Abstract

A low-sodium diet is an essential part of the treatment of hypertension. However, some concerns have been raised with regard to the possible reduction of iodine intake during salt restriction. We obtained 24-h urine collections for the evaluation of iodine (UIE) and sodium excretion (UNaV) from 136 hypertensive patients, before and after 9 ± 1 weeks of a simple low-sodium diet. Body mass index (BMI), blood pressure (BP), and drug consumption (DDD) were recorded. Data are average ± SEM. Age was 63.6 ± 1.09 year. BMI was 25.86 ± 0.40 kg/m2 before the diet and 25.38 ± 0.37 kg/m2 after the diet (p < 0.05). UNaV decreased from 150.3 ± 4.01 mEq/24-h to 122.8 ± 3.92 mEq/24-h (p < 0.001); UIE decreased from 186.1 ± 7.95 µg/24-h to 175.0 ± 7.74 µg/24-h (p = NS); both systolic and diastolic BP values decreased (by 6.15 ± 1.32 mmHg and by 3.75 ± 0.84 mmHg, respectively, p < 0.001); DDD decreased (ΔDDD 0.29 ± 0.06, p < 0.05). UNaV and UIE were related both before (r = 0.246, p = 0.0040) and after the diet (r = 0.238, p = 0.0050). UNaV and UIE were significantly associated both before and after the diet (p < 0.0001 for both). After salt restriction UIE showed a non-significant decrease remaining in an adequate range. Our dietary suggestions were aimed at avoiding preserved foods, whereas the cautious use of table salt was permitted, an approach which seems safe in terms of iodine intake.

Impact of Moderate Sodium Restriction and Hydrochlorothiazide on Iodine Excretion in Diabetic Kidney Disease: Data from a Randomized Cross-Over Trial

“…Results from a salt intervention study in children and their families in northern China demonstrated that ≈25% reduction in salt intake does not compromise iodine status [17]. Reduction of ≈18% in patients on antihypertensive treatment in Italy did not significantly reduce iodine excretion [19]. These data confirm the lack of conflict between population-wide strategies of decreasing salt intake and adequate iodized salt consumption and are in line with our data, where subjects reduced salt intake with approximately 30%.…”

“…Literature that links habitual salt intake to urinary iodine excretion is scarce [12,13,14,15,16,17,18,19] and generalization of results is difficult because of differences in dietary sources of iodine. In a survey in Samoa, no detectable difference in iodine intake in population subgroups defined by salt intake above or below 5 g/d was found [13].…”

“…Two studies addressed the potential effect of sodium restriction on 24-h iodine excretion. One was performed in children and their families in China in primary prevention [18] and the other in patients on antihypertensive treatment in Italy [19]. In patients with diabetic kidney disease, dietary salt restriction is an essential constituent of diabetes care because it lowers blood pressure and slows the progression of proteinuria and kidney function decline [20].…”

Urinary Iodine Concentration in a Cohort of Adult Outpatients with Thyroid Diseases in Liguria 14 Years after the Law on Salt Iodization

“…Moreover, in recent surveys in northeastern Italy, 70-80% of families declared that they used iodized salt daily [9,11], while in a study conducted in Calabria the percentage of families using iodized salt was 64-82% in rural-urban areas [23]. Of the 136 subjects attending our Center for Secondary Hypertension, 62% declared using iodized salt, since, at the beginning of the study, all these patients had had a consultation with a dietitian and had received written nutritional advice [16].…”

“…However, we have very little direct information on the iodine intake of the adult population of Liguria. In 2018, in a cohort of 136 adults referred to our Center for Secondary Hypertension, we observed that, after salt restriction (by avoiding preserved foods), 24-h iodine excretion showed a non-significant decrease [16]. Indeed, 24-h iodine excretion lower than 100 µg was recorded in only 28 subjects (21%), suggesting an average iodine sufficiency in this cohort [16].…”