Estimation of appropriate dietary intake of iodine among lactating women in China based on iodine loss in breast milk.

OBJECTIVE: Data on iodine loss in breast milk, which are critical for establishing the appropriate dietary iodine intake for lactating women, is currently limited. A study was conducted to assess iodine loss in breast milk among Chinese lactating women to estimate the appropriate dietary intake of iodine. METHODS: A total of 54 pairs of healthy, lactating women and their infants aged 0-6 months were recruited from Tianjin and Luoyang cities in China. A 4 days infant weighing study was conducted to assess iodine loss in the breast milk of lactating women. Mothers were required to weigh and record their infants' body weights before and after each feeding for a 24 h period from 8:00 am to 8:00 am. During the weighing study, 2812 breast milk samples and 216 24-h urine samples were collected from each lactating mother for four consecutive days. In addition, a 3 days 24 h dietary record, including salt weighing and drinking water samples collecting, was performed by each lactating mother to determine dietary iodine intake during the weighing study. RESULTS: The average dietary iodine intake of lactating women was 323 ± 80 µg/d. The median breast milk iodine concentration and 24 h urinary iodine concentration of lactating women were 154 (122-181) and 135 (104-172) µg/L, respectively. The mean volume of breast milk and the mean iodine loss in the breast milk of lactating women were 711 ± 157 mL/d and 112 ± 47 µg/d, respectively. The appropriate dietary intake of iodine among lactating Chinese women is approximately 260 µg/d. CONCLUSIONS: Based on the iodine loss in breast milk (110 µg/d) found in this study, and the estimated average requirement of iodine for adults, the appropriate dietary intake of iodine among lactating Chinese women is 260 µg/d, which is higher than the 240 µg/d recommended by the China Nutrition Science Congress in 2013.

Effects of Iodized Salt and Iodine Supplements on Prenatal and Postnatal Growth: A Systematic Review.

Hypothyroidism due to iodine deficiency can impair physical development, most visibly in the marked stunting of myxedematous cretinism caused by severe in utero iodine deficiency. Whether iodine repletion improves growth in noncretinous children is uncertain. Therefore, the aim of our systematic review was to assess the effects of iodine fortification or supplementation on prenatal and postnatal growth outcomes in noncretinous children. Following Cochrane methods and PRISMA (Preferred Reporting Items for Systematic Reviews and Meta-Analyses) reporting guidelines, we searched 10 databases including 2 Chinese databases (latest search February 2017). We included randomized and nonrandomized controlled trials (RCTs; non-RCTs), controlled before-after (CBA) studies, and interrupted time-series studies in pregnant women and children (≤18 y), which compared the effects of iodine (any form, dose, regimen) to placebo, noniodized salt, or no intervention on prenatal and postnatal growth outcomes. We calculated mean differences with 95% CIs, performed random-effects meta-analyses, and assessed the quality of evidence with the use of GRADE (Grading of Recommendations Assessment, Development and Evaluation). We included 18 studies (13 RCTs, 4 non-RCTs, 1 CBA) (n = 5729). Iodine supplementation of severely iodine-deficient pregnant women increased mean birthweight [mean difference (MD): 200 g; 95% CI: 183, 217 g; n = 635; 2 non-RCTs] compared to controls, but the quality of this evidence was assessed as very low. Iodine repletion across the other groups showed no effects on primary growth outcomes (quality of evidence mostly low and very low). Meta-analyses showed a positive effect in moderate-to-mildly iodine-deficient schoolchildren on insulin-like growth factor-1 (MD: 38.48 ng/mL; 95% CI: 6.19, 70.76 ng/mL; n = 498; 2 RCTs, low-quality evidence) and insulin-like growth factor binding protein-3 (MD: 0.46 µg/mL; 95% CI: 0.25, 0.66 µg/mL; n = 498; 2 RCTs, low-quality evidence). In conclusion, we identified few well-designed trials examining the effects of iodine repletion on growth. We are uncertain whether prenatal iodine repletion increases infant growth. Postnatal iodine repletion may improve growth factors but has no clear effects on somatic growth. Our systematic review was registered with PROSPERO as CRD42014012940.

Systematic review of the effects of iodised salt and iodine supplements on prenatal and postnatal growth: study protocol.

INTRODUCTION: Iodine is an essential micronutrient and component of the thyroid hormones. Sufficient ingestion of iodine is necessary for normal growth and development. If iodine requirements are not met, growth can be impaired. Salt iodisation and supplementation with iodine can prevent iodine deficiency disorders and stunted growth. No systematic review has yet collated the evidence linking iodine to growth. With an increased emphasis on stunting within the WHO Global Nutrition Targets for 2025, we propose a systematic review to address this question. METHODS AND ANALYSIS: We will undertake a systematic review, and if appropriate, meta-analyses, evaluating the effects of iodised salt or iodine supplements on prenatal and postnatal somatic growth, until age 18. We will search a number of databases, including MEDLINE, EMBASE, Web of Science, CINAHL, PsychINFO, the Cochrane Library, including the CENTRAL register of Controlled Trials and also the WHO library and ICTRP (International Clinical Trials Registry Platform), which includes the Clinicaltrials.gov repository. We will also search Wanfang Data and the China Knowledge Resource Integrated Database. Included studies must have compared exposure to iodised salt, iodine supplements or iodised oil, to placebo, non-iodised salt or no intervention. Primary outcomes will be continuous and categorical markers of prenatal and postnatal somatic growth. Secondary outcomes will cover further measures of growth, including growth rates and indirect markers of growth such as insulin-like growth factor-1 (IGF-1). ETHICS AND DISSEMINATION: The systematic review will be published in a peer-reviewed journal, and will be sent directly to the WHO, United Nations Children's Fund, International Council for the Control of Iodine Deficiency Disorders and other stakeholders. The results generated from this systematic review will provide evidence to support future programme recommendations regarding iodine fortification or supplementation and child growth. TRIAL REGISTRATION NUMBER: PROSPERO CRD42014012940.

Exploration of the safe upper level of iodine intake in euthyroid Chinese adults: a randomized double-blind trial.

BACKGROUND: The beneficial health effects associated with Universal Salt Iodization are well known. Yet, little is known about the possible adverse health effects in people with high iodine intake and the safe daily intake upper limit in the Chinese population. OBJECTIVE: The objective of this study was to explore the safe upper level of total daily iodine intake among adults in China. DESIGN: A 4-wk, double-blind, placebo-controlled, randomized controlled trial was conducted in 256 euthyroid adults. Participants were randomly assigned to 12 intervention groups with various iodine supplement doses ranging from 0 to 2000 µg/d. Total iodine intake included iodine from both supplements and diet. Multiple outcome measures were used to evaluate possible adverse effects, including thyroid function, thyroid size, and urinary iodine. RESULTS: The mean iodine intake from the diets and salt intake of the participants were 105 ± 25 and 258 ± 101 µg/d, respectively. In comparison with the placebo group, all iodide-supplemented groups responded with significant increases in median urinary iodine concentrations (P < 0.05) and in thyroid-stimulating hormone concentration (P < 0.05). Thyroid volume decreased after 4 wk in the high-iodine intervention groups (1500-2000 µg). Subclinical hypothyroidism appeared in the groups that received 400 µg I (5%) and 500-2000 µg I (15-47%). CONCLUSIONS: This study showed that subclinical hypothyroidism appeared in the participants who took the 400-µg I supplement, which provided a total iodine intake of ∼800 µg/d. Thus, we caution against a total daily iodine intake that exceeds 800 µg/d in China and recommend further research to determine a safe daily upper limit.

[The effect of selenium on the expression of Fas/FasL in experimental autoimmune thyroiditis rats' thyroid with adequate iodine].

OBJECTIVE: To study the effect of different selenium intake on the expression of apoptosis protein Fas/FasL in experimental autoimmune thyroiditis (EAT) rats' thyroid with adequate iodine. METHODS: Thirty-two female lewis rats were divided stochastically into 4 groups as C group, M group, Se(+) + M group, Se(-) + M group, respectively, and pretreated with feedstuffs containing different concentrations of selenium (Se(+) + M group 2 mg/kg, C and M group 0.20 mg/kg, Se(-) + M group 0.02 mg/kg, respectively) for two weeks, and immunized the rats with porcine thyroglobulin (pTg) to establish an EAT model. The thyroid gland was sampled, embedded in mineral wax and sliced, and the expression of Fas/FasL was measured with immunohistochemistry. RESULTS: Both the expressions of Fas and FasL of EAT rats were significantly increased as compared with control group. The expression of Fas in rats' thyroid follicular cells with EAT was down-regulated as the increased selenium intake (optical density: 0.059 +/- 0.006), the expression of Fas of Se(+) + M group (0.036 +/- 0.004) was significantly inhibited (q = 11.591, P = 0.000), and expression of Fas was lower in the Se(+) + M group than Se(-) + M group (0.050 +/- 0.005) (q = 7.055 , P = 0.000). Effect of selenium on FasL was not identified. CONCLUSION: Increasing the intake of selenium might decrease the expression of Fas on thyroid follicular cells and restrain the development of EAT.

[Study on content of iodine in food in Tianjin market and iodine nutrition conditions among college students].

OBJECTIVE: To know about content of iodine in foods sold in Tianjing markets presently, and the iodine nutrition conditions in college students. It was also aimed to probe the functions of the iodized salt complement with the dietary iodine intake, and whether the urine iodine could reflect dietary iodine intake. METHODS: 278 food samples in markets were collected by a randomly stratified sampling method, while the arsenic-cerium catalytic contact method was used to determine the content in food. The dietary information of students for seven days was recorded, and the urine iodine was determined through the arsenic-cerium catalytic spectrophotometry. RESULTS: The determination of 47 kinds and 278 food samples indicated that the content of iodine within animal foods (7.8 microg/100 g - 30.8 microg/100 g) was higher than that within plant foods (1.8 microg/100 g - 16.1 microg/100 g). The investigation also showed that students who regarded vegetarian food as principle accounted for 70. 19%. The amount of dietary iodine intake among those students, based on the dietary survey, was (111.67 +/- 53.18) microg/d, while supplementary iodine from iodized salt was about (230.27 +/- 45.55) microg/d. Therefore, the total iodine provided from diet would be (341.95 +/- 89.58) microg/d. Modified by urine creatinine, the median of urine iodine was 271.28 microg/gCr, and the urine iodine and dietary iodine intake was found positively related (r(s) = 0.463, P < 0.01). CONCLUSIONS: Regarding the vegetarian food as the principle, most of students investigated are not rich. The dietary iodine intake is lower than RDA (150 microg), but it can be obtained the iodized salt by 230. 27 microg, which is the possible supplement to the shortage from foods.