Recommended number of participants in iodine nutrition studies is similar before and after an iodine fortification programme

Background

Iodine fortification programs have been applied in many iodine deficient regions. Iodine excess is also unfavourable, and it is recommended to monitor iodine status by measuring urinary iodine concentration (UIC). The number of samples needed in such monitoring depends on the variation in UIC. However, it is not known if variation in UIC differs according to iodine levels.

Aim and method

We aimed to describe the effect of an iodisation program on the individual and group-based variation in UIC in spot urine samples. Group 1 (G1, n = 16) was studied before, and group 2 (G2, n = 21) was studied after an iodine fortification program was implemented. Individual urine samples were collected monthly for one year, 13 samplings.

Results

G1s (207 samples) median (interquartile range) UIC was 50 (37–67) μg/L, and G2 (265 samples) was 98 (69–139) μg/L. Median individual coefficient of variation (CV) was 38 % in G1 and 40 % in G2 (p = 0.55), whereas the group-based CV was 50 % in G1 and 53 % in G2. No trend was seen between mean UIC and variation in UIC, neither at the individual (p = 0.36) nor at the group level (p = 0.43). Based on data from both groups, approximately 100 samples were needed to reliably estimate the UIC in a population.

Conclusion

In two groups studied before and after an iodine fortification program was implemented and with different UIC levels, variation in UIC was comparable both at the individual level and according to UIC level. When mild iodine deficiency is corrected, the number of samples needed to reliably estimate the UIC in a population is unaffected.     

Reliability of studies of iodine intake and recommendations for number of samples in groups and in individuals

The iodine intake level in a population is determined in cross-sectional studies. Urinary iodine varies considerably and the reliability of studies of iodine nutrition and the number of samples needed is unsettled. We performed a longitudinal study of sixteen healthy men living in an area of mild to moderate iodine deficiency. Iodine and creatinine concentrations were measured in spot urine samples collected monthly for 13 months. From these data we calculated the number of urine samples needed to determine the iodine excretion level for crude urinary iodine and for 24 h iodine excretion estimated from age- and gender-specific creatinine excretions. We found that mean urinary iodine excretion varied from 30 to 87 microg/l (31 to 91 microg/24 h). Sample iodine varied from 10 to 260 microg/l (20 to 161 microg/24 h). Crude urinary iodine varied more than estimated 24 h iodine excretion (population standard deviation 32 v. 26; individual standard deviation 29 v. 21; Bartlett's test, P < 0.01 for both). The number of spot urine samples needed to estimate the iodine level in a population with 95 % confidence within a precision range of +/- 10 % was about 125 (100 when using estimated 24 h iodine excretions), and within a precision range of +/- 5 % was about 500 (400). A precision range of +/- 20 % in an individual required twelve urine samples or more (seven when using estimated 24 h iodine excretions). In conclusion, estimating population iodine excretion requires 100-500 spot urine samples for each group or subgroup. Less than ten urine samples in an individual may be misleading.     

Persistence of iodine deficiency in Gangetic flood-prone area, West Bengal, India

In 2000, India revoked the ban on production and sale of non-iodised salt. We conducted a study in the north 24 Parganas district in the state of West Bengal to assess the prevalence of goitre, status of urinary iodine excretion (UIE) level and to estimate iodine content of salts at the household level. We surveyed 363 school children aged eight to ten years selected using a multistage cluster sampling technique. We estimated goitre prevalence and urinary iodine excretion (UIE) using methods and criteria recommended by the World Health Organization. We estimated the iodine content of salt samples collected from the households of the study subjects using spot iodine testing kit. Of the 363 children, 73 (20%) had goitre. The median UIE was 160 micro g/l (normal: > or =100 micro g/l) and only 6% children had a level below 50 micro g/l. Only 253 of 363 salt samples (70%) were sufficiently iodised. The combination of high goitre prevalence with normal median urinary excretion indicates that the North 24 Parganas district is in transition from iodine deficient to iodine sufficient state. However, the persistence of non-iodised salt consumption indicates that an intensification of universal salt iodisation program is needed. In 2000, India revoked the ban on production and sale of non-iodised salt. We conducted a study in the north 24 Parganas district in the state of West Bengal to assess the prevalence of goitre, status of urinary iodine excretion (UIE) level and to estimate iodine content of salts at the household level. We surveyed 363 school children aged eight to ten years selected using a multistage cluster sampling technique. We estimated goitre prevalence and urinary iodine excretion (UIE) using methods and criteria recommended by the World Health Organization. We estimated the iodine content of salt samples collected from the households of the study subjects using spot iodine testing kit. Of the 363 children, 73 (20%) had goitre. The median UIE was 160 micro g/l (normal: > or =100 micro g/l) and only 6% children had a level below 50 micro g/l. Only 253 of 363 salt samples (70%) were sufficiently iodised. The combination of high goitre prevalence with normal median urinary excretion indicates that the North 24 Parganas district is in transition from iodine deficient to iodine sufficient state. However, the persistence of non-iodised salt consumption indicates that an intensification of universal salt iodisation program is needed.     

The sensitivity and specificity of thyroglobulin concentration using repeated measures of urinary iodine excretion

Purpose

Iodine deficiency affects 30% of populations worldwide. The amount of thyroglobulin (Tg) in blood increases in iodine deficiency and also in iodine excess. Tg is considered as a sensitive index of iodine status in groups of children and adults, but its usefulness for individuals is unknown. The aim of this study was to determine the diagnostic performance of Tg as an index of iodine status in individual adults.

Methods

Adults aged 18–40 years (n?=?151) provided five spot urine samples for the measurement of urinary iodine concentration expressed as μg/L (UIC), μg/g of creatinine (I:Cre), and μg/day (estimated UIE); the mean of the five samples was used as the reference standard. Participants also provided a blood sample for the determination of Tg, thyroid-stimulating hormone (TSH), and free thyroxine (FT4).

Results

The median of UIC, I:Cre, estimated UIE, and Tg was 72 (range 16–350) μg/L, 90 (range 33–371) μg/g, 129 (range 41–646) μg/day, and 16.4 (range 0.8–178.9) μg/L, respectively. Using Tg cut-offs of >10, >11, >13, and >15 μg/L, the sensitivity and specificity for UIC, I:Cre, and estimated UIE ranged from 52 to 79% and 20–48%, respectively, below the acceptable value of ≥80%. Furthermore, receiver-operating characteristic (ROC) curves for Tg using the three measurements of urinary iodine were situated close to the chance line and the area under the curve ranged from 0.49 to 0.52.

Conclusions

The results from this cross-sectional study indicate that Tg has low sensitivity and specificity to repeated measures of urinary iodine excretion. Further studies are still needed to investigate the usefulness of Tg as a biomarker of individual iodine status.

     

Day-to-day and within-day variation in urinary iodine excretion.

OBJECTIVE: To examine the day-to-day and within-day variation in urinary iodine excretion and the day-to-day variation in iodine intake. DESIGN: Collection of consecutive 24-h urine samples and casual urine samples over 24h. SETTING: The study population consisted of highly motivated subjects from our Institute. SUBJECTS: Study 1: Ten healthy subjects (seven females and three males) aged 30-46 y. Study 2: Twenty-two healthy subjects (9 males and 13 females) aged 30-55 y. METHODS: Study 1: 24-h urine samples were collected for four consecutive days. Study 2: Each urine voided over 24 h was collected into separate containers. In both studies dietary records were kept. MAIN OUTCOME MEASURES: Twenty-four-hour urinary iodine excretion, 24-h urinary iodine excretion estimated as I/Cr*24 h Cr and as a concentration in casual urine samples. RESULTS: Study 1: Both iodine excreted in 24-h urine and iodine intake varied from day-to-day. Iodine excretion correlated with iodine intake (=-0.46, P=0.01). Iodine intake (mean 89 +/- 6.5 microg/d) was not significantly different from iodine excretion (mean 95 +/- 5.3 microg/d). Study 2: Twenty-four hour iodine excretion estimated as I/Cr*24 h Cr from the morning urine sample was significantly lower than actual 24-h iodine excretion, whereas 24-h iodine excretion estimated as I/Cr*24 h Cr from the first sample after the morning sample and the last sample before the subjects went to bed was not significantly different from actual 24-h iodine excretion. Twenty-four-hour urine excretion estimated as a concentration was lower than actual 24-h iodine excretion in casual urine taken at any time of the day. CONCLUSIONS: For determination of iodine status in an individual, more than one 24-h urine sample must be used. The use of the I/Cr ratio in casual urine samples is a usable measure of iodine status if corrected for the age- and sex-adjusted 24-h creatinine excretion. Further, the study suggests that fasting morning urine samples would underestimate iodine status in this population.     

Current trends of 24-h urinary iodine excretion in German schoolchildren and the importance of iodised salt in processed foods

Worldwide, the iodisation of salt has clearly improved iodine status. In industrialised countries, iodised salt added to processed food contributes most to iodine supply. Yet it is unclear as to what extent changes in the latter may affect the iodine status of populations. Between 2004 and 2009, 24-h urinary iodine excretions (UIE) were repeatedly measured in 278 German children (6 to 12 years old) of the Dortmund Nutritional and Anthropometric Longitudinally Designed Study (n 707). Na excretion measurements and simultaneously collected 3-d weighed dietary records provided data on intakes of the most important dietary sources of iodine in the children's diet. Actual trends of UIE (2004-9) and contributions of relevant food groups were analysed by mixed linear regression models. Longitudinal regression analysis showed a plateau of UIE in 2004-6; afterwards, UIE significantly decreased till 2009 (P = 0·01; median 24-h UIE in 2004-6: 85·6 μg/d; 2009: 80·4 μg/d). Median urinary iodine concentration fell below the WHO criteria for iodine sufficiency of 100 μg/l in 2007-9. Salt, milk, fish and egg intake (g/d) were significant predictors of UIE (P < 0·005); and the main sources of iodine were salt and milk (48 and 38 %, respectively). The present data hint at a beginning deterioration in the iodine status of German schoolchildren. A decreased use of iodised salt in industrially produced foods may be one possible reason for this development. Because of the generally known risks for cognitive impairment due to even mild iodine deficits in children, a more widespread use of iodised salt, especially in industrially processed foods, has to be promoted.     

Longitudinal examination of 24-h urinary iodine excretion in schoolchildren as a sensitive, hydration status-independent research tool for studying iodine status

BACKGROUND: Because worldwide iodine status (IS) depends on continuous fortification, the adequacy of IS needs to be regularly monitored. OBJECTIVE: Our study aimed to evaluate IS in a longitudinal sample of healthy schoolchildren who regularly used table salt iodized with 20 microg I/g. DESIGN: Urine osmolality (Uosm) and 24-h urinary excretion rates of iodine (24-h UI), sodium, creatinine, and total urine volume (24-h Uvol) were measured in 1046 specimens that were collected at repeated intervals from 1996 to 2003 in a sample of 358 German children aged 6-12 y. Energy intake and food consumption were calculated from 3-d weighed dietary records that were collected in parallel to the urine samples. RESULTS: During the 4-y period from 1996 to 1999, the median 24-h UI increased from 87 to 93 microg I/d (P = 0.017), whereas urinary iodine concentration (UIC), Uosm, and 24-h Uvol did not change significantly. Thereafter (from 2000 to 2003), UIC stagnated and Uosm decreased (P = 0.004), whereas 24-h Uvol (P = 0.008) and 24-h UI (P = 0.002) increased. The final median 24-h UI reached 120 microg I/d. Milk, fish, egg, and meat intakes and 24-h sodium excretion were all significant predictors of IS, with an almost doubled contribution from milk intake during the second 4-y period. CONCLUSIONS: Our study shows a continuous improvement of IS in a longitudinal sample of German schoolchildren. This improvement was masked when UIC was used as an IS index, especially from 2000 to 2003 because of changes in hydration status. Thus, in research-oriented studies that focus on UIC measurements, hydration status can be a relevant confounder. Longitudinal analyses of 24-h UI in cohort studies may represent an alternative hydration status-independent tool to examine trends in IS and the contribution of relevant foods to IS.     

Quantification of urinary iodine: a need for revised thresholds

OBJECTIVE: To compare different possibilities of reporting the iodine supply in the same urine samples. Indeed, in field studies, urinary iodine concentration (I/L: micro g I/L, micro mol I/L, I/creatinine: micro g I/g creatanine, micro mol I/mol creatinine) is more readily available than excretion (I/24h micro g I/24 h, micro mol I/24h). However, confusion exists regarding the comparability of iodine supply based upon I/L, I/creatinine and I/24h, which for decades have been regarded as biochemically equivalent. DESIGN: We compared I/24h, I/L and I/creatinine in accurate 24 h collections of urine and I/L and I/creatinine in 47 spot urine samples. PATIENTS: A total of 13 subjects (Bern n=7, Brussels n=6) collected a total of 110 precise 24 h urine collections (Bern n=63, Brussels n=47). The subjects from Brussels also took a spot sample at the beginning of each 24 h collection. RESULTS: Iodine supply in both places was mildly deficient according to the criteria of WHO; all but one collection indicated an intake of >0.39 micro mol I/24h (>50 micro g I/24h). The same data presented as I/creatinine (or I/L) indicated an iodine intake of <0.39 (<50 micro g I/24h) in 5% (24%) of the samples in Bern and 23% (57%) in Brussels. Similar findings were observed for 47 spot samples. Whatever the cut-off selected, I/creatinine and I/L were systematically lower than I/24h (P<0.0002). Creatinine showed smaller CV than volume but did not perform better in defining iodine intake. CONCLUSION: Considering I/24h as a reference, both I/creatinine and I/L clearly underestimate the iodine intake in subjects with adequate proteoenergetic intake. The significant deviations observed illustrate the urgent need for establishing separate ranges for I/24h, I/creatinine and I/L. In population studies, these deviations might even be larger.     

Suboptimal iodine status of Australian pregnant women reflects poor knowledge and practices related to iodine nutrition

ObjectiveTo assess the iodine status and knowledge and practices related to iodine nutrition of Australian women during pregnancy.MethodsA cross-sectional study was conducted at a public antenatal clinic in the Illawarra region of New South Wales. One hundred thirty-nine pregnant women across all trimesters provided a spot urine sample (n = 110) and completed a short questionnaire (n = 139) in English. Iodine status was based on World Health Organization/International Committee for the Control of Iodine Deficiency Disorders urine iodine concentration (UIC) categories.ResultsMedian UIC was 87.5 μg/L (interquartile range 62); only 14.5% of participants had an adequate UIC value ≥150 μg/L. Fifteen percent of women had very low UIC values (<50 μg/L), whereas 45.5% had values in the 50- to 99-μg/L range. Knowledge of the adverse health effects of an inadequate iodine intake was poor. Approximately half the participants were able to indicate good dietary sources of iodine, such as fish (58%) and iodized salt (51%). However, a high level of confusion regarding other foods was evident. Only a small number of participants (11%) reported that they had intentionally changed their diet to increase iodine intake during pregnancy, but 59% indicated supplement use, of which 35% contained iodine. Those who were taking supplements that contained iodine had significantly higher UIC levels (139.1 μg/L) than those who were not (90.8 μg/L, P < 0.05).ConclusionPublic health strategies, including nutritional education and supplementation, are urgently required to improve the iodine status of pregnant women. Currently, no readily accessible information on iodine is available to women attending antenatal clinics in Australia.     

Restricted intraindividual urinary iodine concentration variability in nonfasting subjects

OBJECTIVE: Individual urinary iodine concentration (UIC) reflects iodine intake over a short time prior to sampling. Since eating habits are relatively constant in single subjects, UIC should be relatively constant in a given individual. The aim of our study was to verify this hypothesis by assessing UIC in repeated single urine samples from a group of healthy subjects. DESIGN AND SETTING: A prospective sequential investigation was performed in 131 volunteer health workers or students recruited in our University hospital. INTERVENTIONS: Single urine samples were taken in a nonfasting state, between 0900 and 1100 hours. Group 1 was composed by 131 subjects who collected one urine sample. Group 2 was composed by 11 subjects of the group 1, who collected multiple repeated urine samples (as a whole 158 urine samples, mean 14 samples each). UIC mean+/-s.d., median and coefficient of variation (CV%) was measured in both groups. RESULTS: Interindividual UIC variation was wide, UIC ranging from 21 to 382 microg/l, mean 136+/-84 microg/l, median 124 microg/l, CV 62%. Also in the 11 subjects repeatedly sampling there were considerable differences among individual UIC average levels (ranging from 37+/-15 to 221+/-91 microg/l). However, in this second group, the intraindividual variation was considerably restricted (CV% 36). CONCLUSIONS: The present study shows that in a nonfasting state in mid-morning UIC is more stable from day to day in a single subject, depending on his eating habits, than in various subjects. Thus, a single urine sample even in nonfasting state may give some rough information about the individual's iodine status.     

Thyroid hormones and iodine status in Sudanese pregnant women with goitre

Thyroid hormones in relation to iodine status were studied in a group of Sudanese pregnant women with goitre (n = 66). These women were compared with a healthy, non-pregnant control group from the same area (n = 40). Twenty-four-hour urine samples and serum samples were collected during weeks 10-13, 20-24 and 32-39 of pregnancy. The goitrous group had a significantly lower mean urinary iodine concentration (UIC) than the non-pregnant group during weeks 20-24 and 32-39 (P < 0.003 and P < 0.001), respectively. The thyroid-stimulating hormone (TSH) and T3 levels in the pregnant group showed a stable pattern with the progression of pregnancy. TSH values in all the pregnant women were within the reference range. The mean FT4 levels of the goitrous pregnant group, in weeks 20-24 and 32-39 of pregnancy, were significantly lower than that of the non-pregnant control group (P < 0.003 and P < 0.05), respectively. The proportions of the pregnant women with FT4 below the reference range were 31, 50 and 40% in weeks 10-13, 20-24 and 32-39 of pregnancy, respectively. There was no correlation between UIC and TSH, UIC and FT4 and between TSH and FT4 during pregnancy. By virtue of the proportion of subjects falling below and above the reference range, this study indicates that in this particular study area, UIC and FT4 are better indicators of iodine status than TSH.     

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

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.     

Median Urinary Iodine Concentrations Are Indicative of Adequate Iodine Status among Women of Reproductive Age in Prey Veng,Cambodia

Iodine deficiency disorders are estimated to affect over 1.9 million people worldwide. Iodine deficiency is especially serious for women during pregnancy and lactation because of the negative consequences for both mother and infant. The aim of this cross-sectional study was to determine the median urinary iodine concentration (UIC) as a population-level indicator of iodine status among rural women farmers of reproductive age (18–45 years) in the province of Prey Veng, Cambodia. A total of 450 women provided a spot morning urine sample in 2012. Of those women, 93% (n = 420) were non-pregnant and 7% (n = 30) were pregnant at the time of collection. UIC was quantified using the Sandell-Kolthoff reaction with modifications. The median UIC of non-pregnant (139 μg/L) and pregnant women (157 μg/L) were indicative of adequate iodine status using the WHO/UNICEF/ICCIDD epidemiological criteria for both groups (median UIC between 100–199 and 150–249 μg/L, respectively). We conclude that non-pregnant and pregnant women in rural Prey Veng, Cambodia had adequate iodine status based on single spot morning urine samples collected in 2012. More research is warranted to investigate iodine status among larger and more representative populations of women in Cambodia, especially in light of recent policy changes to the national program for universal salt iodization.     

Nationwide Representative Survey of Dietary Iodine Intake and Urinary Excretion in Postpartum Korean Women

Iodine is an essential component of thyroid hormones, but excessive iodine intake can lead to thyroid dysfunction. Traditionally, Korean mothers consume brown seaweed soup (miyeokguk), a high source of iodine, after childbirth. There is controversy regarding the effects of excessive postpartum iodine intake on the health of mothers and infants. Thus far, there have been no nationwide large-scale surveys regarding the status of iodine intake among postpartum women in Korea. Therefore, we conducted a nationwide survey of postpartum dietary iodine intake among Korean women. In total, 1054 Korean women aged ≥19 years, at less than 8 weeks postpartum, participated in this survey. Dietary data were collected using self-reported 2-day dietary records, along with before-and-after meal photos. To evaluate the correlation between dietary iodine and urinary iodine excretion (UIE), spot urine, and 24 h urine samples were collected from 98 and 29 participants, respectively. The mean daily iodine intake among all participants was 2945.6 μg, and it gradually decreased over time after childbirth. Dietary iodine intake was significantly correlated with 24 h UIE (r = 0.396, p < 0.05) and spot urine UIE (r = 0.312, p < 0.05). Follow-up studies are required to examine the influence of excessive postpartum iodine intake on thyroid health in mothers and their infants.     

Formulas developed based on the ratio of urea nitrogen to creatinine concentrations obtained from multiple spot urine samples are acceptable to predict protein intake at group level but not at individual level

In this study, we hypothesized that spot urine can be used to predict protein intake at both group and individual levels. Participants (n = 369) of this study were recruited from all 47 prefectures in Japan. Sex-specific formulas were developed based on the ratio of urea nitrogen to creatinine concentration obtained from 3 spot urine samples. Validity of the formulas was examined against two 24-hour urine collections for 7 combinations of spot urine (single and means of 2 or 3 samples) using t test (mean estimation), Spearman correlation, and Bland-Altman plot (individual bias). Means of measured protein intake based on 24-hour urinary excretions were 87.3 g/d (standard deviation 19.7) for men and 70.5 g/d (standard deviation 14.7) for women. Irrespective of sex, the predicted intakes were not significantly different (within 2.7% of differences) from those measured by urinary excretions. Predicted intakes were moderately correlated with measured intakes (men, 0.45-0.60; women, 0.35-0.53). Even after using the mean of 3 samples, Bland-Altman plots showed a considerably wide limit of agreement (men, −30 to 33 g/d; women, −27 to 24 g/d). Except for using single spot urine samples in women, the formula tended to overestimate intake at a lower and underestimate at a higher level of protein intake (slope: men, −0.47 [P < .0001]; women, −0.38 [P = .002]). In conclusion, predictive formulas developed in this study can be used to predict protein intake at group level or to rank individuals' intake but not to predict absolute intake at individual level.     

江苏省部分地区婴幼儿碘营养状况及影响因素分析

【目的】 调查江苏省婴幼儿碘营养状况及影响因素,为本地区婴幼儿合理的碘摄取提供参考意见。 【方法】 采用分层随机抽样的方法,收集2 329名婴幼儿,检测尿碘浓度,询问并填写调查表,体格测量,分析尿碘水平及影响因素。 【结果】 1)江苏省5地区婴幼儿尿碘浓度四分位数间距(Q75~Q25)为250~100μg/L,尿碘中位数(MUI)为200 μg/L;尿碘浓度(UIC)＜100μg/L的比例为12.2%,UIC＞300 μg/L者占5.2%。2)不同月龄尿碘分布情况存在差异(χ²=19.870,P<0.05),不同地区尿碘分布情况存在差异(χ²=60.355,P<0.001)。3)Logistic回归分析显示:尿碘值可能与儿童月龄、居住地区及添加食盐有关,与父母文化程度无关。 【结论】 江苏省五地区婴幼儿平均碘营养状况处于适宜水平,仍存在碘缺乏和碘过量的现象;不同地区尿碘分布情况不同,城市尤以南京市婴幼儿碘缺乏和碘过量比例较高。     

天津市非水源性高碘地区成人碘营养状况及总膳食碘折算方法

  目的  了解天津市非水源性高碘地区成人居民碘营养状况及来源分布,并比较3 d膳食调查法和24 h尿碘法折算总膳食碘的方法学差异。  方法  根据中国成人慢性病与营养监测方案,在天津市河西区、南开区、红桥区、武清区、津南区、宝坻区、蓟州区共计调查1 634名成人,使用3 d膳食回顾法和调味品称重法相结合获得总膳食碘状况,描述居民碘营养状况及各部分碘的贡献率,从中随机抽取403名调查者收集24 h尿液进行尿碘检测,比较3 d膳食调查法和尿碘折算法估计总膳食碘的方法学差异。  结果  天津市非水源性高碘地区成人居民总膳食碘摄入量为207.13 μg/标准人日,70.3%的被调查者处于碘适宜状态;盐碘是总膳食碘最主要的来源（78.2%）,其次是食物碘（13.2%）和水碘（8.6%）;整体上看,3 d膳食调查法比24 h尿碘折算法高估约10%。  结论  天津市非水源性高碘地区成人居民碘营养状况总体处于适宜水平,盐碘是膳食碘最主要的来源,3 d膳食调查法和24 h尿碘折算法估计总膳食碘摄入量差异不大。     

Iodine status in Melbourne adults in the early 1990s and 2007-08

Objective: To investigate the iodine status of Melbourne adults in 1992–94 and 2007–08, and to assess dietary iodine intake to enable comparison with recommended Nutrient Reference Values. Method: A cross‐sectional study utilising 24‐hr urine samples collected at two time points in a random sample of the Melbourne Collaborative Cohort Study. Two hundred and fifty seven adults (128 males, 129 females) in 1992–94, with a mean age of 56 years, and 265 adults (132 males, 133 females) in 2007–08, with a mean age of 68 years, were assessed, all being Melbourne residents. Urinary iodine concentration (UIC) was determined and daily urinary iodine excretion and daily iodine intake were assessed. Results: In 1992–94, the median UIC was 27 μg/L and 84% had UIC <50 μg/L. The median daily iodine intake was 51 μg/d, and 83% of participants had dietary iodine intakes below the Estimated Average Requirement of 100 μg/d. In 2007–08, the median UIC was 49 μg/L, 51% had UIC <50 μg/L and the median daily iodine intake was 98 μg/d, with 52% of intakes below the EAR. Conclusion: Melbourne adults were moderately iodine deficient in 1992–94, and borderline moderately deficient in 2007–08. Implications: While iodine status appears to have improved, it remains below an adequate level for much of the adult population of Victoria. Adequate monitoring is fundamental to assess whether the mandatory use of iodised salt in bread is effective in reducing iodine deficiency across all population groups.     

Iodine status in preschool children and evaluation of major dietary iodine sources: a German experience

Purpose

Even mild iodine deficiency may negatively affect cognitive performance, especially at a young age. Our aim was to investigate iodine status in very young children and to assess the importance of iodized salt in processed foods of which the use has decreased during the last years in Germany.

Methods

Twenty-four hours urinary iodine excretion (UIE) as a marker of iodine intake was measured in 378 24 h urine samples collected 2003–2010 by 221 3 to <6 years old participants of the DONALD Study. Parallel 3-d weighed dietary records and measurements of urinary sodium excretion provided data on the daily consumption of the most important iodine sources in the children’s diet (iodized salt, milk, fish, meat and eggs). Time trends of UIE (2003–2010) and contributions of the different food groups were analyzed by using linear mixed-effects regression models.

Results

Median UIE of 71 μg/d in boys and 65 μg/d in girls (P = 0.03), corresponding to an iodine intake of 82 and 75 μg/d, respectively (assumption: 15 % non-renal iodine losses), was below the recommended dietary allowance (RDA) of 90 μg/d. Milk, salt and egg intake were significant predictors of UIE; milk and salt together accounted for >80 % of iodine supply. Between 2003 and 2010, UIE decreased significantly by approximately 1 μg/d per year. The contribution of salt intake to UIE decreased from 2003–2006 to 2007–2010.

Conclusion

In countries where salt is a major iodine source, already modest decreases in the iodized proportion of salt used in processed foods may relevantly impair iodine status even in preschool children.     

An evaluation of salt intake and iodine nutrition in a rural and urban area of the C?te d'Ivoire.

OBJECTIVE: To evaluate the habitual salt intake of individuals living in the C?te d'Ivoire, and to monitor the iodine nutrition of adults, schoolchildren and pregnant women one year after implementation of a universal salt iodisation programme. DESIGN: A three day weighed food records with estimation of food intake from a shared bowl based on changes on body weight, determination of sodium and iodine concentrations in 24 h (24 h) urine samples from adults, and determination of urinary iodine in spot urines from schoolchildren and pregnant women. SETTING: A large coastal city (Abidjan) and a cluster of inland villages in the northern savannah region of the C?te d'Ivoire. SUBJECTS: For the food records: 188 subjects (children and adults) in the northern villages; for the 24 h urine collections: 52 adults in Abidjan and 51 adults in the northern villages; for the spot urine collections: 110 children and 72 pregnant women in Abidjan and 104 children and 66 pregnant women in the north. MAIN RESULTS: From the food survey data in the north, the total mean salt intake (s.d.) of all age groups and the adults was estimated to be 5.7 g/d (+/- 3.0), and 6.8 g/d (+/- 3.2), respectively. In the 24 h urine samples from adults, the mean sodium excretion was 2.9 g/d (+/- 1.9) in the north and 3.0 g/d (+/- 1.3) in Abidjan, corresponding to an intake of 7.3-7.5 g/d of sodium chloride. In the north the median 24 h urinary iodine excretion in adults was 163 microg/d, and the median urinary iodine in spot urines from children and pregnant women was 263 microg/l and 133 microg/l, respectively. In contrast, in Abidjan the median 24 h urinary iodine was 442 microg/d, with 40% of the subjects excreting > 500 microg/d, and the median urinary iodine in spot urines from children and pregnant women was 488 microg/l and 364 microg/l, respectively. Nearly half of the children in Abidjan and 32% of the pregnant women were excreting > 500 microg/l. CONCLUSION: Based on the estimates of salt intake in this study, an optimal iodine level for salt (at the point of consumption) would be 30 ppm. Therefore the current goals for the iodised salt programme--30-50 ppm iodine appear to be appropriate. However, in adults, children and pregnant women from Abidjan, high urinary iodine levels--levels potentially associated with increased risk of iodine-induced hyperthyroidism--are common. These results suggest an urgent need for improved monitoring and surveillance of the current salt iodisation programme in the C?te d'Ivoire.