Iodine status of UK schoolgirls: a cross-sectional survey

The impact of replacing milk with plant-based alternatives on iodine intake: a dietary modelling study

PURPOSE

Cow's milk is the primary source of iodine in the UK, but consumption of plant-based milk alternatives (PBMA) is increasing and these products are often not fortified with iodine. We evaluated the impact that replacing current milk consumption with PBMA would have on iodine intake.

METHODS

We used data from the National Diet and Nutrition Survey (2016-2019) for children (1.5-10 years), girls 11-18 years, and women of reproductive age (WRA). We used a dietary modelling approach with scenarios using brand-level iodine-fortification data (0, 13, 22.5, 27.4 and 45 µg/100 mL). Relative to usual diet, we calculated change in iodine intake, and the proportion with intake below the Lower Reference Nutrient Intake (LRNI) or above the upper limit.

RESULTS

For all groups, replacement with PBMA, either unfortified or fortified at the lowest concentration, resulted in a meaningful decrease in iodine intake, and increased the proportion with intake < LRNI; compared to usual diet, iodine intake reduced by 58% in children 1.5-3 years (127 vs. 53 µg/day) and the proportion with intake < LRNI increased in girls (11-18 years; 20% to 48%) and WRA (13% to 33%) if an unfortified PBMA was used. Replacement of milk with PBMA fortified at 27.4 µg/100 mL had the lowest impact.

CONCLUSION

Replacing milk with commercially available PBMAs has potential to reduce population iodine intake, depending on the fortification level. PBMAs fortified with ≥ 22.5 and < 45 µg iodine/100 mL would be required to minimize the impact on iodine intake. Research is needed on the impact of total dairy replacement.

Iodine and plant-based diets: a narrative review and calculation of iodine content

An increasing number of food-based recommendations promote a plant-based diet to address health concerns and environmental sustainability in global food systems. As the main sources of iodine in many countries are fish, eggs and dairy products, it is unclear whether plant-based diets, such as the EAT-Lancet reference diet, would provide sufficient iodine. This is important as iodine, through the thyroid hormones, is required for growth and brain development; adequate iodine intake is especially important before, and during, pregnancy. In this narrative review, we evaluated the current literature and estimated iodine provision from the EAT-Lancet reference diet. There is evidence that those following a strict plant-based diet, such as vegans, cannot reach the recommended iodine intake from food alone and are reliant on iodine supplements. Using the EAT-Lancet reference diet intake recommendations in combination with iodine values from UK food tables, we calculated that the diet would provide 128 μg/d (85 % of the adult recommendation of 150 μg/d and 51–64 % of the pregnancy recommendation of 200–250 μg/d). However, if milk is replaced with unfortified plant-based alternatives, total iodine provision would be just 54 μg/d (34 % and 22–27 % of the recommendations for adults and pregnancy, respectively). Plant-based dietary recommendations might place consumers at risk of iodine deficiency in countries without a fortification programme and where animal products provide the majority of iodine intake, such as the UK and Norway. It is essential that those following a predominantly plant-based diet are given appropriate dietary advice to ensure adequate iodine intake.

Iodine status and associated dietary factors among preschool children in Shanghai

Children aged 3-6 years undergo a critical stage of growth and development and are irreversibly affected by their iodine status. In order to reveal iodine status in preschool children, we detected iodine concentrations in urine samples from 1382 children aged 3-6 years based on a cross-sectional study. The median urinary iodine concentration (UIC) of children was 193.36 μg/L and was 336.96 μg/g·Cr corrected for creatinine. The study developed a link between dietary habits and iodine status, revealing that regular calcium supplement (OR: 1.79, (95% CI: 1.03, 3.12)) increased deficiency risk, while moderate seafood consumption (OR: 0.60, (95% CI: 0.38, 0.95)) decreased it. Additionally, modest intake of shellfish (OR: 0.58, (95% CI: 0.33, 1.00)), vegetables (OR: 0.61, (95% CI: 0.38, 0.97)), and eggs (OR: 0.53, (95% CI: 0.30, 0.95)) was found to protect against excess iodine. The findings underline the importance of balanced diets and various nutrients' roles in preschoolers' iodine status.

Iodine in plant-based dairy products is not sufficient in the UK: A market survey

BACKGROUND

Following a well-balanced diet ensures that a person gets all the essential elements for health sustenance. However, in the United Kingdom an increasing proportion of people are transiting to become vegans who exclude animal-based products in their diets. Consequently, people may have a deficit of essential elements such as iodine which is not present in most plant-based meals, additionally iodide fortified table salt is not commonly used in the UK. Without iodine people consuming a vegan diet risk developing iodine deficiency and diseases like goiter.

METHODS

The objective of this study is to determine the difference in iodine content and iodine speciation between plant-based and dairy products. More than 100 market samples of plant-based and dairy milk products were collected in Scotland, UK.

RESULTS

Iodine concentrations in dairy milk is ten times higher compared to plant-based milks. Similar differences were also apparent for butter, yogurt and cheese. A total of 20% of plant-based milk products were fortified with iodine, however these products had lower iodine concentrations compare to the equivalent dairy products. In this study we calculated that people with average diet have an iodine intake of 226 + /- 103 μg day^-1 from dairy products which satisfies the WHO recommended intake of adults and 90% of the recommend intake for pregnant and breast-feeding women. A diet from substituted dairy products gives only 21.8 µg day^-1 for the respective WHO guideline intake values, which accounts only 15% of the iodine intake for adults and 9% for pregnant and lactating women. Iodine fortified diet could increase the iodine intake to 55% or 33% of the WHO recommended daily intake respectively.

CONCLUSION

Plant-based dairy consumers are encouraged to use iodine fortified dairy products or use of iodized salt in the UK for home cooking, otherwise there are at risk to get iodine deficient.

Variation in macrominerals and trace elements in cows' retail milk and implications for consumers nutrition

Based on previous farm-level studies, this study hypothesised that production system (conventional, CON; organic, ORG; channel island, CHA) and season would cause variation in the concentrations of macrominerals and trace elements in retail milk. On average, milk retained its status as an excellent source of Ca, P, I, and Mo across different demographics, and a very good source of K, Mg, and Zn for children. Compared with CON and ORG, CHA milk contained higher concentrations of Ca, Mg, P, Cu, Mn, and Zn; and lower concentrations of K and I. Macrominerals did not show a clear seasonal pattern but trace elements were all at lower concentrations during the typical grazing season. Variation in mineral concentrations can have implications to Ca and P supply in children, and I and Zn supply across different consumer demographics; while the seasonal variation was more pronounced than that associated with production system.

Assessment of Dietary Intake of Iodine and Risk of Iodine Deficiency in Children with Classical Galactosaemia on Dietary Treatment

Iodine is an essential mineral required for the synthesis of thyroid hormones. Iodine plays a critical role in growth and neurocognitive development. Classical galactosaemia is a disorder resulting from an inborn error in galactose metabolism. Its current management consists of life-long lactose and galactose dietary restriction. This study estimated dietary intakes of iodine in infants and children with classical galactosaemia in the Republic of Ireland. The diets of 43 participants (aged 7 months-18 years) with classical galactosaemia were assessed for iodine intake using an iodine-specific food frequency questionnaire. Intakes were compared to the European Food Safety Authority (EFSA) dietary recommendations for iodine intake. The potential role of iodine fortification of dairy alternative products was also examined. There were no significant differences observed between sex, ethnicity and parental education and meeting dietary iodine recommendations. Differences, however, were seen between age groups, causing the p value to approach statistical significance (p = 0.06). Infants consuming infant formula were likely to meet iodine recommendations. However, over half (53%) of children aged 1-18 years had average intakes below the recommendations for age. For these children, consumption of iodine-fortified dairy alternative milk was the leading source of iodine in the diets, followed by fish/shellfish and eggs. An assessment of iodine intake should be undertaken during dietetic reviews for those with classical galactosaemia. Mandatory iodine fortification of all dairy alternative products would result in 92% of the total population cohort meeting iodine recommendations based on their current consumption.

Universal salt iodization potentially contributes to health equity: socio-economic status of children does not affect iodine status

OBJECTIVES

Many studies have shown that socio-economic status (SES) contributes to health inequalities, with nutrition as one of the major risk factors. Iodine intake entirely depends on external sources, and deficiencies are known to be more prevalent in lower social groups, especially in countries with limited access to iodized salt. This study aimed to determine the influence of SES on iodine status and iodine availability from household salt in North Macedonia.

METHODS

Using cluster sampling, 1,200 children were recruited, and 1,191 children participated (response rate: 99.2%). Iodine status was assessed through urinary iodine concentration (UIC), and iodine availability through iodine content in household salt requested from participants. SES was assessed using standardized Family Affluence Score (FAS).

RESULTS

No statistically significant correlation was found between FAS and iodine in salt. Median regression revealed no significant associations of middle vs. low FAS (β=0.00; 95%-confidence interval (CI)=[-0.61, 0.62]; p=0.999) or high vs. low affluence (β=0.48; 95% CI=[-1.37, 0.41]; p=0.291) with iodine content in household salt. UIC levels were significantly lower in middle FAS children compared to low FAS children (β=-16.4; 95% CI=[-32.3, -0.5]; p=0.043). No statistically significant differences in UIC were found between children with high and low affluence (β=-12.5; 95% CI=[-35.5, 10.5]; p=0.287), possibly due to lowered statistical power for this comparison.

CONCLUSIONS

Universal salt iodization (USI) proves to be a cost-effective measure for appropriate iodine intake in healthy children and adults, irrespective of their social status. It can thus be concluded that USI contributes to reducing health inequalities related to iodine status among population of different social strata.

Thyroidal and Extrathyroidal Requirements for Iodine and Selenium: A Combined Evolutionary and (Patho)Physiological Approach

Iodide is an antioxidant, oxidant and thyroid hormone constituent. Selenoproteins are needed for triiodothyronine synthesis, its deactivation and iodine release. They also protect thyroidal and extrathyroidal tissues from hydrogen peroxide used in the ‘peroxidase partner system’. This system produces thyroid hormone and reactive iodine in exocrine glands to kill microbes. Exocrine glands recycle iodine and with high urinary clearance require constant dietary supply, unlike the thyroid. Disbalanced iodine-selenium explains relations between thyroid autoimmune disease (TAD) and cancer of thyroid and exocrine organs, notably stomach, breast, and prostate. Seafood is iodine unconstrained, but selenium constrained. Terrestrial food contains little iodine while selenium ranges from highly deficient to highly toxic. Iodine vs. TAD is U-shaped, but only low selenium relates to TAD. Oxidative stress from low selenium, and infection from disbalanced iodine-selenium, may generate cancer of thyroid and exocrine glands. Traditional Japanese diet resembles our ancient seashore-based diet and relates to aforementioned diseases. Adequate iodine might be in the milligram range but is toxic at low selenium. Optimal selenoprotein-P at 105 µg selenium/day agrees with Japanese intakes. Selenium upper limit may remain at 300–400 µg/day. Seafood combines iodine, selenium and other critical nutrients. It brings us back to the seashore diet that made us what we currently still are.

A review of current knowledge about the importance of iodine among women of child-bearing age and healthcare professionals

Iodine is required for thyroid hormone synthesis and fetal neurogenesis. Recent population studies in the United Kingdom (UK) have found iodine deficiency among schoolgirls, women of child-bearing age and pregnant women. This review explores knowledge and awareness of iodine among women of child-bearing age and healthcare professionals (HCPs) in the UK, set within a global context. We aimed to identify gaps in iodine knowledge in the current UK setting of iodine deficiency without iodine fortification and where iodine is not included in antenatal guidelines. The search terms ‘iodine knowledge’ and ‘iodine awareness’ were used to identify relevant papers. Iodine knowledge is poor among women of child-bearing age in the UK according to four studies using questionnaires and qualitative methods. They were unsure of dietary sources of iodine and were not consistently provided with relevant information from HCPs during clinical care. Midwives have been recognised as the main providers of dietary information during pregnancy and, although they recognised the importance of their role in providing nutrition advice, they did not feel equipped to do so and lacked confidence in addressing nutritional concerns. Globally, there was a similar lack of knowledge, however, this was somewhat improved by the inclusion of iodine in antenatal care guidelines. Midwives’ knowledge of iodine was poor, as was knowledge among women of child-bearing age. Improved HCP knowledge and effective communication of information to pregnant women and women planning to conceive may help to improve iodine status which is of particular concern in pregnancy.

MECHANISMS IN ENDOCRINOLOGY: The pathophysiology of transient congenital hypothyroidism

Transient congenital hypothyroidism (TCH) refers to congenital hypothyroidism which spontaneously resolves in the first few months or years of life. Currently, there is a paucity of reliable markers predicting TCH at diagnosis, and the diagnosis is established following the withdrawal of levothyroxine therapy around 3 years of age. The incidence of TCH is increasing, and it is a major contributor to the overall increase in the incidence of CH in recent studies. Both genetic factors, in particular mutations affecting DUOX2 and DUOXA2, and environmental factors, for example, iodine deficiency and excess, anti- TSHR antibodies and exposure to antithyroid or iodine-rich medications, may cause TCH. Resolution of TCH in childhood may reflect both normal thyroid physiology (decreased thyroid hormone biosynthesis requirements after the neonatal period) and clearance or cessation of environmental precipitants. The relative contributions and interactions of genetic and environmental factors to TCH, and the extent to which TCH may be prevented, require evaluation in future population-based studies.

The Impact of Iodine Concentration Disorders on Health and Cancer

Iodine deficiency is an ongoing problem. The implementation of salt iodization has significantly reduced the effects of iodine deficiency worldwide in recent years, and the remaining iodine deficiency is mild to moderate. Iodine is an essential substrate for the synthesis of thyroid hormones in the thyroid gland. It can also act as an antioxidant, as well as an anti-proliferative and pro-apoptotic factor. Pregnant women, breastfeeding women, and children are particularly affected by iodine deficiency. It leads to thyroid diseases and metabolic and developmental disorders, as well as cancer. However, an excessive iodine intake may, similarly to iodine deficiency, lead to the development of goiter, and toxic amounts of iodine can lead to thyroiditis, hyperthyroidism, and hypothyroidism, and even to the development of papillary thyroid cancer. Correcting iodine deficiency potentially reduces the chance of developing malignancies. Additional research is needed to better understand both the effect of iodine on carcinogenesis and the clinical outcome of iodine deficiency compensation on cancer patients' prognosis. The upcoming public health challenge appears to be reducing salt consumption, which could result in a lower iodine intake. Thus, an iodine enrichment vehicle other than salt could be considered if salt iodine levels are not increased to compensate, and urine iodine levels should be monitored more frequently.

Thyroglobulin levels among iodine deficient pregnant women living in Northern Ireland

BACKGROUND

Iodine deficiency has re-emerged among pregnant cohorts in the UK. Thyroglobulin (Tg) is a protein produced uniquely by the thyroid gland which appears to mount a U-shaped response to extremes of iodine status. Tg has been suggested as an alternative marker for chronic iodine deficiency but the value of Tg in pregnancy has not been fully elucidated. A recent non-European study suggested a median Tg ≤10 µg/L with <3% of values >44 µg/L was indicative of sufficiency in the second trimester of pregnancy.

METHODS

We measured serum Tg levels in each trimester in 241 pregnant women living in Northern Ireland, a population with mild iodine deficiency at all stages of pregnancy as defined by urinary iodine concentration (UIC) and iodine: creatinine ratio (ICR). Women with Tg antibodies (6% in 1st trimester) were excluded.

RESULTS

The median UIC in this cohort was in the deficient range at 73, 94 and 117 µg/L in sequential trimesters (adequacy ≥ 150 µg/L). Corresponding median Tg levels were 19, 16 and 16 µg/L respectively. Median Tg for all samples was 17 μg/L (IQR 11-31) suggestive of iodine deficiency. Tg was >44 μg/L in 14.3%, 9.4% and 12.4% of women in sequential trimesters respectively. Women with either UIC/ICR below the cut-offs 150 µg/L and 150 µg/g creatinine had higher Tg concentrations in 1st and 2nd trimester (p < 0.01; p < 0.001) but not in 3rd trimester.

CONCLUSION

This study adds to the evolving evidence that Tg measurement is of value in reflecting iodine status in pregnancy.

Assessment of iodine fortification of salt in the Danish population

PURPOSE

We assessed the effect of the current iodine fortification level (20 µg/g household salt and salt included in bread and bakery products) on inadequate and excessive intake in the general Danish population. Intake models with/without the contribution from food supplements and effects of excluding specific food groups were evaluated.

METHOD

Data from the Danish National Survey of Dietary Habits and Physical Activity in 2011-13 (N = 3946, aged 4-75 years) stratified by age-group and sex were used to estimate habitual dietary iodine intakes, and compared with established dietary reference values.

RESULTS

The proportion with an estimated inadequate iodine intake was ≤ 3% for males and ≤ 5% for females, except for 15-17-year-old girls, where the probable prevalence of an inadequate intake was 11%. Including the contribution from food supplements gave similar results (10%). High intakes (as defined by 95th percentile) from food sources generally did not exceed the tolerable upper intake level (UL). However, for the youngest age-groups (4-6-year-old boys/girls and 7-10-year-old boys), the 95th percentiles exceeded the UL with 11%, 4% and 7%, respectively, when food supplements were included in the estimates. Especially exclusion of dairy products and bread led to an inadequate intake for both boys and girls.

CONCLUSION

The current fortification level may provide an inadequate iodine intake for some females and on the other hand lead to excessive intakes in the youngest age-groups. The study shows the importance of choosing iodine-rich alternatives when excluding major sources of iodine in the Danish diet.

Dairy as a Source of Iodine and Protein in the UK: Implications for Human Health Across the Life Course, and Future Policy and Research

This narrative review summarizes key concepts in dairy nutrition for supporting human health throughout the life course. Milk and dairy products have been a staple component of our diet for thousands of years and provide a wide range of important nutrients that are otherwise difficult to obtain from dairy-free diets. In this review, we provide a broad perspective on the nutritional roles of iodine and dairy protein in supporting human health during pregnancy and early life, childhood and adolescence, mid- and later-life. New methodologies to identify biomarkers of dairy intake via high-throughput mass spectrometry are discussed, and new concepts such as the role of the food matrix in dairy nutrition are introduced. Finally, future policy and research related to the consumption of dairy and non-dairy alternatives for health are discussed with a view to improving nutritional status across the lifespan.

Vegans and vegetarians living in Nottingham (UK) continue to be at risk of iodine deficiency

Iodine is essential for thyroid hormone synthesis. Individuals adhering to vegan and vegetarian diets have been found to be vulnerable to iodine deficiency. Yet, iodine has not been monitored in these groups across time. This study aims to investigate iodine status, intake and knowledge in vegans, vegetarians and omnivores and determine changes between 2016-2017 and 2019. Dietary intake (µg/d) was estimated by 3-d food diaries and iodine FFQ. Urinary iodine concentration, analysed by inductively coupled plasma mass spectrometry, assessed iodine status according to WHO criteria. Iodine knowledge was scored by an adapted questionnaire. IBM SPSS was used for statistical analysis. Ninety-six adults (18-60 years) were recruited in October 2016-2017 (vegans: 12; vegetarians: 5; omnivores: 43) and June 2019 (vegans: 7; vegetarians: 10;omnivores: 19). Median dietary iodine was below the Reference Nutrient Intake for all groups. Vegans and vegetarians had the lowest iodine intake. Vegans had significantly lower iodine intake than omnivores (2016-2017, P = 0 032; 2019, P = 0 001). Omnivores had the highest iodine status (2016-2017, 79 4 µg/l; 2019, 72 4 µg/l) and vegans the lowest (2016-2017, 31 2 µg/l; 2019, 12 2 µg/l). Iodine knowledge was poor but did not differ between dietary groups (2016-2017, P = 0 219; 2019, P = 0 532). Vegans and vegetarians continue to be at risk of iodine deficiency. Further, iodine intake in the UK is poor independent of dietary choice. Iodine education is needed along with research into improving iodine nutrition at national level.

The Characteristics of Iodine Nutrition Status in China After 20 Years of Universal Salt Iodization: An Epidemiology Study Covering 31 Provinces

Background: Despite the implementation of the universal salt iodization (USI) program for correction of iodine deficiency in China for ∼20 years, the actual iodine nutrition status of Chinese residents and the prevalence of iodine deficiency and iodine excess are issues that need to be addressed. This nationally representative cross-sectional study was conducted across all 31 provinces of mainland China to gather extensive data on iodine nutrition status and the influential factors. Methods: This study included 78,470 participants, aged 18 years or older, who were interviewed and asked to answer a questionnaire. Urine iodine concentration (UIC) was measured by the inductively coupled plasma mass spectrometry method, and goiter was examined by thyroid ultrasonography. In addition, sixty 9-11 years old school children in each province were randomly selected to evaluate the UIC and thyroid ultrasonography. The iodine nutrition status was determined according to the World Health Organization guidelines. Results: The iodized salt coverage was 95.37%. The median urine iodine (MUI) was 177.89 μg/L (interquartile range [IQR], 117.89-263.90 μg/L) and goiter prevalence was 1.17% (confidence interval [95% CI 0.95-1.43]) in the adult population. The MUI was 199.75 μg/L (IQR, 128.41-303.37 μg/L) in school-age children, and goiter prevalence was 3.50% [95% CI, 2.93-4.13]. The percentage of individuals with UIC <50 μg/L was 3.43%, <20%. Analysis indicated that sex, age, geographic factors, body mass index, and smoking habits influence the iodine nutrition level. Conclusion: The mandatory USI program has successfully eliminated iodine deficiency disorders, and the findings indicate that the iodine nutrition level in the general population is within the safe range.

A comparative assessment of the nutritional composition of dairy and plant-based dairy alternatives available for sale in the UK and the implications for consumers' dietary intakes

The popularity of plant-based dairy alternatives (PBDAs) products has grown exponentially in recent years creating a new market of PBDA. The aim of this study was to compare the nutritional content of plant-based alternatives of milk, yogurt and cheese with dairy equivalents and the impact on nutritional intake across the lifespan when they are substituted into UK diets. Nutritional information from cow's milk, yogurt, cheese and PBDAs available on the UK market was collected via manufacturers information. The products were categorised according to primary plant-based ingredient/s and compared with the equivalent dairy product. The National Diet and Nutrition Survey data was used to calculate the intake of milk, yogurt and cheese across all age groups and the energy and nutrient intake was calculated. Plant-based milk, cheese and yogurt alternative categories were then substituted for dairy intakes, and energy and nutrient intakes were calculated and compared to UK Dietary Reference Values. A total of 299 PBDA products were identified consisting of 136 milk alternatives, 55 yogurt alternatives and 109 cheese alternatives. All PBDAs were more expensive than dairy products. Milk contained more energy, saturated fat, carbohydrates, protein, vitamin B₂, vitamin B₁₂ and iodine, and less fibre and free sugars, than plant-based milk alternatives (P < 0.05). There were significant differences between yogurt and cheese and their corresponding PBDAs for energy, fat, saturated fat, carbohydrate, sugars, fibre protein, salt, and calcium (P < 0.05). These differences were reflected in the nutrient intakes of different age groups and the results demonstrated that PBDA may be useful as practical replacements of dairy products but cannot be considered nutritional replacements.

Neonatal heel prick screening TSH concentration in the Netherlands as indicator of iodine status

Background

Neonatal Thyroid Stimulating Hormone (nTSH) is proposed as indicator of iodine deficiency in a population. Population’s iodine sufficiency is indicated by a proportion of the newborns less than 3% having nTSH above 5 mIU/L. The aim of this study was to explore the Dutch neonatal heel prick screening TSH data to assess iodine status in the Netherlands and identify determinants and potential confounders of this assessment.

Methods

All newborns born in the Netherlands between 2007 and 2015 with a heel prick collection at day 3-7 were included (n = 1,435,600), except preterm neonates and baby’s with a low birth weight. Total T4 was measured for all children, nTSH was measured in the ~ 20% children with lowest total T4.

Results

The proportion with nTSH > 5mIU/L fluctuated between 0.6-1.3% in 2007-2015. nTSH was significantly associated with laboratory performing the nTSH assay and age of heel prick sampling. The overall increasing trend in proportion nTSH >1mIU/L was confounded by the laboratories with different and changed assays.

Conclusions

The low proportion neonates with high nTSH suggests a sufficient iodine status in the Netherlands. Whether the increased proportion nTSH>1mIU/L over the years is an early indicator of deterioration of the iodine status remains unclear, due to differences and changes in analytical assays. nTSH might be a valuable and inexpensive way to get crude insight in the (trend in) iodine status, but more research is needed on the validity and potential conditions.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12937-021-00722-4.

Iodine monitoring models contribute to avoid adverse birth outcomes related more than adequate iodine intake

BACKGROUND

Iodine plays an important role in pregnancy. How to maintain adequate iodine intake amongst pregnant women in each trimester of pregnancy to prevent adverse birth outcomes in central China is a challenge for clinical practice.

METHODS

870 pregnant women and their infants were enrolled in the study. Urinary iodine concentration (UIC) was measured using an inductively coupled plasma mass spectrometry (ICP-MS). Maternal and newborn information were obtained during follow-up. Multinomial logistic regression models were established.

RESULTS

Median UIC of pregnant women was 172 ± 135 μg/L which is currently considered to be sufficient. Multivitamin supplements containing iodine, iodized salt intake and frequent milk intake were significantly associated with higher UIC. Multivariate logistic regression analysis showed that multivitamin supplements containing iodine and milk consumption were risk factors for more than adequate iodine (UIC ≥ 250 μg/L). Iodine-rich diet was significantly related to heavier birthweight, larger head circumference and longer femur length of the newborns while more than adequate iodine intake (UIC ≥ 250 μg/L) was a risk factor for macrosomia. Logistic regression models based on potential risk factors involving iodine containing supplements and iodine-rich diet were established to predict and screen pregnant women with high risk of more than adequate iodine intake among local pregnant women in different trimesters and guide them to supplement iodine reasonably to prevent the risk.

CONCLUSIONS

Multivitamin supplements containing iodine and milk consumption were risk factors for maternal UIC ≥ 250 μg/L which was a risk factor for macrosomia. Iodine monitoring models were established to provide guidance for pregnant women to reduce the risk of more than adequate iodine intake, thereby contributing to reduce the risk of having a macrosomia.

Pattern analysis of vegan eating reveals healthy and unhealthy patterns within the vegan diet

OBJECTIVE

This study aimed to identify the types of foods that constitute a vegan diet and establish patterns within the diet. Dietary pattern analysis, a key instrument for exploring the correlation between health and disease, was used to identify patterns within the vegan diet.

DESIGN

A modified version of the EPIC-Norfolk FFQ was created and validated to include vegan foods and launched on social media.

SETTING

UK participants, recruited online.

PARTICIPANTS

A convenience sample of 129 vegans voluntarily completed the FFQ. Collected data were converted to reflect weekly consumption to enable factor and cluster analyses.

RESULTS

Factor analysis identified four distinct dietary patterns including: (1) convenience (22 %); (2) health conscious (12 %); (3) unhealthy (9 %) and (4) traditional vegan (7 %). Whilst two healthy patterns were defined, the convenience pattern was the most identifiable pattern with a prominence of vegan convenience meals and snacks, vegan sweets and desserts, sauces, condiments and fats. Cluster analysis identified three clusters, cluster 1 'convenience' (26·8 %), cluster 2 'traditional' (22 %) and cluster 3 'health conscious' (51·2 %). Clusters 1 and 2 consisted of an array of ultraprocessed vegan food items. Together, both clusters represent almost half of the participants and yielding similar results to the predominant dietary pattern, strengthens the factor analysis.

CONCLUSIONS

These novel results highlight the need for further dietary pattern studies with full nutrition and blood metabolite analysis in larger samples of vegans to enhance and ratify these results.

Factors Associated with Thyroid Disorders and Iodine Adequacy in Pregnant Saudi Women

Little is known about iodine adequacy and gestational thyroid disorders (GTDs) in Saudi Arabia. This study measured the rates of GTDs and iodine adequacy in 810 healthy Saudi women. Concentrations of serum thyroid hormones and 24-h urine iodine (24-h UIC), and GTDs were diagnosed according to the American Thyroid Association guidelines. Dietary and socioeconomic data to determine factors associated with GTDs and iodine insufficiency were collected. GTDs were detected in 265 women (32.7%) as follows: subclinical (SCH; 20.2%) and overt (OH; 5.8%) hypothyroidism, isolated hypothyroxinemia (ISH; 4.7%) and hyperthyroidism (2%). The SCH (109.2 μg/L; IQR: 77.2-149.7), OH (95.3 μg/L; IQR: 74.3-130.5) and ISH (107.3 μg/L; IQR: 65.5-133.1) groups had median 24-h UIC below the WHO recommended limit, whereas the euthyroid (191.4 μg/L; IQR: 170.03-219.8) and hyperthyroid (159.5 μg/L; IQR: 152.9-238.3) groups were iodine sufficient. Numbers of pregnancies, less education, not consuming iodized salt and not using iodine supplements increased risk of hypothyroidism and ISH. Contrariwise, interval ≥ 3 years from last pregnancy and higher 24-h UIC decreased odds of hypothyroidism and ISH. Moreover, dairy products and egg consumption were markedly lower in all GTD groups. Dairy products and seafood consumption correlated independently with 24-h UIC of the study participants, whereas consuming yogurt, eggs, redfish and shellfish protected against GTDs. In conclusion, GTDs appear to be prevalent in pregnant Saudi women and the hypothyroid and hypothyroxinemia groups had iodine insufficiency. However, consuming iodized salt, iodine supplements, dairy products, seafoods and eggs may protect against GTDs.

Efficacy of a Salt Iodization Program on Iodine Status and Intakes in Schoolchildren of São Miguel Island, Azores, Portugal

INTRODUCTION

Iodine is an essential micronutrient and its deficiency can severely impact children's development. In 2012, the Thyroid Study Group of the Portuguese Society of Endocrinology, Diabetes and Metabolism discovered that the median urinary iodine concentration (mUIC) level in schoolchildren of São Miguel was far too low at 70.9 μg/L. In response, the government implemented a salt iodization program to help normalize levels. This investigation evaluated the efficacy of such an approach.

METHODS

Urinary iodine concentration (UIC) was evaluated in 362 schoolchildren from São Miguel using the fast colorimetric method.

RESULTS

mUIC was 106.7 μg/L, significantly higher than that observed in 2012 (p < 0.001). Over half (55.5%) of the schoolchildren had a UIC >100 μg/L versus 23.0% in 2012 (p < 0.001). 9.4% of schoolchildren had a UIC <50 μg/L, significantly lower than the 30.6% reported in 2012 (p < 0.001).

DISCUSSION/CONCLUSION

Five years after the implementation of the government salt iodization program, the mUIC increased from 70.9 to 106.7 μg/L. This study confirms the efficacy of the adopted measures in schoolchildren population.

Iodine status in UK-An accidental public health triumph gone sour

The improvement in iodine status among the UK population from the 1930s onwards has been described as an 'accidental public health triumph' despite the lack of any iodine fortification program. However, iodine deficiency in the UK has re-emerged in vulnerable groups and is likely due to a combination of changing farming practices, dietary preferences and public health priorities. The UK is now among only a minority of European countries with no legislative framework for iodine fortification. The experience of folic acid fortification and the 28-year delay in its implementation lays bare the political difficulties of introducing any fortification program in the UK. If iodine fortification is not an imminent possibility, then it is important to explore other options: how to change farming practice especially on organic farms; encourage dairy intake; protect and expand our public health programs of milk provision for vulnerable groups and embark on education programs for women of childbearing potential and healthcare professionals. This review explores how the UK may have arrived at this juncture and how the iodine status of the nation may be improved at this time of major political and public health upheaval.

MILK Symposium review: The importance of milk and dairy foods in the diets of infants, adolescents, pregnant women, adults, and the elderly

The ongoing increase in life expectancy is not always accompanied by an increase in healthy life span. There is increasing evidence that dietary exposure in early life can substantially affect chronic disease risk in later life. Milk and dairy foods are important suppliers of a range of key nutrients, with some being particularly important at certain life stages. It is now recognized that milk protein can stimulate insulin-like growth factor-1 (IGF-1), essential for longitudinal bone growth and bone mass acquisition in young children, thus reducing the risk of stunting. Low milk consumption during adolescence, particularly by girls, may contribute to suboptimal intake of calcium, magnesium, iodine, and other important nutrients. Given the generally low vitamin D status of European populations, this may have already affected bone development, and any resulting reduced bone strength may become a big issue when the populations are much older. Suboptimal iodine status of many young women has already been reported together with several observational studies showing an association between suboptimal iodine status during pregnancy and reduced cognitive development in the offspring. There is now good evidence that consumption of milk and dairy foods does not lead to an increased risk of cardiovascular diseases and type 2 diabetes. Indeed, some negative associations are seen, notably between yogurt consumption and type 2 diabetes, which should be researched with urgency. Greater emphasis should be placed on reducing malnutrition in the elderly and on dietary approaches to reduce their loss of muscle mass, muscle functionality, and bone strength. Whey protein has been shown to be particularly effective for reducing muscle loss; this needs to be developed to provide simple dietary regimens for the elderly to follow. There is an ongoing, often too simplistic debate about the relative value of animal versus plant food sources for protein in particular. It is important that judgments on the replacement of dairy products with those from plants also include the evidence on relative functionality, which is not expressed in simple nutrient content (e.g., hypotensive and muscle synthesis stimulation effects). Only by considering such functionality will a true comparison be achieved.

Iodine status of Turkish pregnant women and their offspring: A national cross-sectional survey

BACKGROUND

This national cross-sectional survey aimed to assess the iodine status in pregnant women and their offspring, and also to demonstrate regional differences by measuring urinary iodine concentration (UIC). For each woman and her newborn a questionnaire was prepared with basic facts as age, parity number or birth weight and additional information regarding thyroid diseases, use of iodized salt in the household, extra iodine supplementation during pregnancy, education level and wage income.

METHODS

The target population represented 1444 pregnant women who gave birth between January 1 st, 2018 and 2019, and their offspring. Iodine deficiency for pregnant women and their offspring were defined as urine iodine level <150 μg/L and <100 μg/L, respectively. Results are given as median (25th-75th percentile).

RESULTS

The median UIC in the group of pregnant woman was 94 (52-153) μg/L. Within the sample of 1444 pregnant women, UIC indicative of mild iodine deficiency (100-149 μg/L) was present in 21 % (n = 306), moderate deficiency (50-99 μg/L) in 30 % (n = 430), and severe deficiency (<50 μg/L) in 23 % (n = 337). This study showed a prevalence of 74 % of iodine deficiency in Turkish pregnant woman. The median UIC in the group of offspring was 96 (41-191) μg/L. Within the new-borns, UIC indicative of mild iodine deficiency (50-99 μg/L) was present in 22 % (n = 323), moderate deficiency (20-49 μg/L) in 15 % (n = 222), and severe deficiency (<20 μg/L) in 13 % (n = 192). This survey showed a prevalence of 51 % of iodine deficiency in Turkish new-borns. Pregnant women with lower socioeconomic and education level, lower access to household iodized salt, lower rates of exposure to povidone-iodine containing skin disinfectant, higher parity and higher iodine deficiency had higher rates of iodine deficiency in their offspring. Regional differences were observed both in mothers and their offspring concerning their iodine status.

CONCLUSIONS

Our findings suggest that iodine deficiency is still an important public health problem in Turkey. More drastic measures should be taken to decrease these important iodine deficiencies, both in pregnant women and in their offspring.

Iodine status of pregnant women with obesity from inner city populations in the United Kingdom

BACKGROUND/OBJECTIVES

Iodine is essential for foetal neurodevelopment and growth. Requirements increase in pregnancy to support increased thyroid hormone synthesis for maternal and foetal requirements, and for foetal transfer. Iodine deficiency in pregnancy is widely reported, and obesity has been associated with sub-optimal thyroid function. We evaluated iodine status and its relation with birthweight in a secondary analysis of pregnant women with obesity from multi-ethnic inner-city settings who participated in the UK Pregnancies Better Eating and Activity trial (UPBEAT).

SUBJECTS/METHODS

Iodine and creatinine concentrations were evaluated in spot urine samples in the second (15⁺⁰-18⁺⁶ weeks, n = 954) trimester of pregnancy. We assessed iodine status as urinary iodine concentration (UIC) and urinary iodine-to-creatinine ratio (UI/Cr) and applied WHO/UNICEF/IGN population threshold of median UIC > 150 µg/L for iodine sufficiency. Relationships between iodine status and birthweight were determined using linear and logistic regression with appropriate adjustment, including for maternal BMI and gestational age.

RESULTS

Median (IQR) UIC and UI/Cr in the second trimester of pregnancy were 147 µg/L (99-257) and 97 µg/g (59-165), respectively. An UI/Cr <150 μg/g was observed in 70% of women. Compared to women with UI/Cr >150 µg/g, there was a trend for women with UI/Cr <150 µg/g to deliver infants with a lower birthweight (β = -60.0 g; 95% CI -120.9 to -1.01, P = 0.05).

CONCLUSIONS

Iodine status of pregnant women with obesity from this cohort of UK women was suboptimal. Lower iodine status was associated with lower birthweight.

Selenium status in a Northern Irish pregnant cohort with iodine deficiency

Selenium and iodine are trace elements that are maximally concentrated in the thyroid. Iodine is a substrate for thyroid hormone synthesis, while the selenoproteins protect the thyroid from the oxidative stress incurred. We measured plasma selenium concentration in 241 pregnant women in 1st trimester, previously reported to have iodine deficiency. Mean age was 30.3 years (SD 5.4), BMI 26.2 kg/m² (SD 4.9) and 53% reported taking supplements. Median urinary iodine concentration was 73 μg/L (IQR 37-122) (WHO recommendation, ≥150 μg/L). Mean plasma selenium concentration was 75 µg/L (SD 7.7) which is below the 80-125 µg/L reported to be optimal. Four-day food diaries revealed a selenium intake of 43 µg/day (SD 15.9), also below the 55-70 µg/day reported to be optimal. This is the first report of selenium status in pregnancy on the island of Ireland. The possible combined effects of iodine and selenium deficiencies in pregnancy merit further investigation.

Urinary sodium and iodine concentrations among Belgian adults: results from the first national Health Examination Survey

BACKGROUND/OBJECTIVES

Iodine deficiency and excessive salt intakes have adverse health consequences. The objective was to measure sodium and iodine concentrations in urine spot samples among a representative sample of Belgian adults and compare those to World Health Organization (WHO) recommendations.

SUBJECTS/METHODS

Spot urine samples were collected in 2018 from participants of the Belgian Health Examination Survey. Iodine and sodium concentrations were measured by inductively coupled plasma mass spectrometry and ion selective electrodes respectively. Tanaka and INTERSALT equations were used to predict 24-h urinary sodium excretion using sodium and creatinine concentration in spot samples, sex, and measured height and weight.

RESULTS

Median urinary iodine concentration (UIC) among adults (n = 1092) was 93.6 µg/L, indicating mild iodine deficiency according to WHO thresholds. Median UIC among participants who reported thyroid problems over the last year was significantly higher than among those who did not report thyroid problems (104.1 µg/L versus UIC = 92.2 µg/L, p < 0.001). There were no significant differences in median UIC between sexes, age groups, and regions. The average salt intake among Belgian adults (n = 1120) was 8.3 ± 0.1 g/day using the Tanaka equation and 9.4 ± 0.1 g/day using the INTERSALT equation. For both equations, <5% of the population met the recommended WHO upper salt intake level of 5 g/day.

CONCLUSIONS

Iodine nutrition in the Belgian adult, nonpregnant population likely indicates mild iodine deficiency as the median UIC was below the WHO threshold for iodine sufficiency. Salt intake was substantially higher than the WHO recommendations. Further policy efforts are needed to optimize iodine and reduce salt intake in Belgium.

Plant-based milks: the dental perspective

Background Consumption of plant-based milk in the UK is increasing at the expense of cow's milk. Cow's milk consumption has traditionally been advocated by the dental profession as 'good for teeth'.Aims To identify the range of plant-based milks available in the UK and compare their nutritional benefits with cow's milk. A secondary aim was to explore reasons behind the increase in popularity of plant-based milks and discuss dental relevance.Methods Branded plant-based milks available in UK supermarkets were identified and nutritional data collected. Data were obtained from product labelling and manufacturer websites. The sample was collected in December 2019.Results Eighty-two products were identified. Differences were observed between plant-based and cow's milk, in particular regarding calcium, iodine, vitamin B12 and sugar content. Sugar content varied from 0-7.6 g/100 ml.Conclusions Dairy is a key source of dietary iodine and many plant-based milks contain much lower levels. Many plant-based milks contain free sugars which are cariogenic. Dentists should be aware of this emerging market and be able to advise patients accordingly.

Feed-derived iodine overrides environmental contribution to cow milk

Diets worldwide are deficient in iodine, leading to a range of undesirable health effects at the population level. Dairy products are a primary source of iodine in diets for those populations in which iodized salt is not systematically used or available. However, the flows of iodine through dairy agroecosystems are not well understood. The aim of this research was to investigate iodine flows though the dairy agroecosystem, including the influence of atmospheric depositional inputs, environmental variables, season, husbandry, and diet. Three farm-based sampling campaigns were carried out in this investigation, with milk, soil, silage, grass, and feed iodine determined by inductively coupled plasma mass spectroscopy, and nonparametric statistical analysis tests were conducted on data sets obtained. Natural iodine inputs into the environment are dominated by atmospheric deposition, which mainly from sea spray, and thus the location of farms relative to the coast and prevailing wind direction. Herbage and silage produced from grass-based systems strongly correlated with soil iodine, yet there was a strong disconnect between soil, forage, and feed and the milk that results. This was due to the levels of iodine in supplemental feeds being approximately 10-fold higher than those in forage-derived feeds. The practice of feed supplementation, accentuated by summer housing of cows, led to elevated milk iodine.

Geographical and seasonal variation in iodine content of cow's milk in the UK and consequences for the consumer´s supply

BACKGROUND

Dairy products provide a crucial source of dietary iodine for the majority of the UK population, contributing approximately 30-40 % of daily intake. Fluctuations in the iodine content of purchased milk both seasonally and annually implies potential fragility of iodine supply likely through fluctuating supplementation practices in cow herds. We set out to establish the level of national variation in herds and identify factors which might impact milk iodine content.

METHODS

Milk samples were obtained from 98 herds across the UK via the National Milk Laboratories in August and December 2016. Iodine concentration of samples was measured using ICP-MS. Milk samples and feed intake data were additionally taken from 22 cows from the University of Nottingham (UON) dairy herd.

RESULTS

There was considerable variation in milk iodine content from < 0.012 (Limit of Detection) to 1558 μg L^-1, with a summer median of 197 μg L^-1 and winter median 297 μg L^-1. Overall, winter values were higher than summer counterparts (P < 0.001) and this held true for samples taken from the North West (P = 0.002) and South West (P = 0.006) but not for other regions studied. Data from the UON herd showed a negative relationship between iodine content and milk yield (P = 0.03) and we found that milk iodine content varied considerably despite apparently similar iodine intakes.

CONCLUSIONS

Regional differences in milk iodine concentration between summer and winter suggests that feeding practices are far from uniform across the country. The negative association observed between iodine concentration and milk yield in UON samples, suggests that reduced summer values may be influenced by dilution in addition to seasonal differences in concentrate feed provision.

Santos I, E. Black R, D. Chrestani MA, A. Duarte F, F. Nilson EA. Iodine Status of Brazilian School-Age Children: A National Cross-Sectional Survey

Salt iodization is the main public health policy to prevent and control iodine deficiency disorders. The National Salt Iodization Impact Assessment Survey (PNAISAL) was conducted to measure iodine concentration among Brazilian schoolchildren. A survey including 6–14-year-old schoolchildren from public and private schools from all 26 Brazilian states and the Federal District was carried out in the biennia 2008–2009 and 2013–2014. Municipalities, schools, and students were randomly selected. Students were interviewed at school using a standard questionnaire, which included the collection of demographic, educational, weight, height, and 10 mL non-fasting urine collection information. The analyses were weighted according to the population of students per federative unit. The median urinary iodine concentration (MUIC) for the entire sample by region, federative unit per school, and student characteristics, was described from the cutoff points defined by the World Health Organization (severe disability: <20 µg/L, moderate: 20–49 µg/L, mild: 50–99 µg/L, adequate: 100–199 µg/L, more than adequate: 200–299 µg/L, and excessive: >300 µg/L). In total, 18,864 students (95.9% of the total) from 818 schools in 477 municipalities from all federative units were included in this study. Almost 70% were brown skin color, nine-years-old or older, studied in urban schools, and were enrolled in elementary school. The prevalence of overweight/obesity, as measured by body mass index (BMI) for age, was about twice as high compared to nutritional deficits (17.3% versus 9.6%). The MUIC arrived at 276.7 µg/L (25th percentile = 175.5 µg/L and 75th percentile = 399.71 µg/L). In Brazil as a whole, the prevalence of mild, moderate, and severe deficit was 6.9%, 2.6%, and 0.6%, respectively. About one-fifth of the students (20.7%) had adequate iodine concentration, while 24.9% and 44.2% had more than adequate or excessive concentration, respectively. The prevalence of iodine deficits was significantly higher among younger female students from municipal public schools living in rural areas with the lowest BMI. The median urine iodine concentration showed that Brazilian students have an adequate nutritional intake, with a significant proportion of them evidencing overconsumption of this micronutrient.

Iodine status of non-pregnant women and availability of food vehicles for fortification with iodine in a remote community in Gulf province, Papua New Guinea

Adequate iodine status of women of childbearing age is essential for optimal growth and development of their offspring. The objectives of the current study were to assess the iodine status of non-pregnant women, availability and use of commercial salt, extent to which it is iodised, and availability of other industrially processed foods suitable for fortification with iodine. This prospective cross-sectional study was carried out in 2018 in a remote area in Gulf province, Papua New Guinea. Multistage cluster sampling was used to randomly select 300 women visiting local markets. Of these, 284 met study criteria of being non-pregnant and non-lactating. Single urine samples were collected from each of them. Discretionary salt intake was assessed; salt samples were collected from a sub-sample of randomly selected households. A semi-structured, pre-tested questionnaire to assess use and availability of commercial salt and other processed foods was modified and used. Salt was available on the interview day in 51.6% of households. Mean iodine content in household salt samples was 37.8 ± 11.8 ppm. Iodine content was below 30.0 ppm in 13.1% and below 15.0 ppm in 3.3% of salt samples. Mean iodine content of salt available at markets was 39.6 ± 0.52 ppm. Mean discretionary intake of salt per capita per day was 3.9 ± 1.21 g. Median UIC was 34.0 μg/L (95% CI, 30.0-38.0 ppm), indicating moderate iodine deficiency. For women with salt in the household, median UIC was 39.5 μg/L (95% CI, 32.0-47.0 μg/L), compared to median UIC of 29.0 μg/L (95% CI, 28.0-32.0 μg/L) for those without salt. This community has low consumption of iodised salt, likely due to limited access. Investigation of other industrially processed foods indicated salt is the most widely consumed processed food in this remote community, although 39.8% of households did use salty flavourings.

Iodine deficiency among pregnant women living in Northern Ireland

OBJECTIVE

Mild iodine deficiency has re-emerged among school girls in the UK. We wished to study a contemporaneous pregnant population because a relationship between maternal iodine deficiency and offspring cognitive scores has recently been reported. The WHO has set a median population urinary iodine concentration (UIC) of ≥100 and ≥150 µg/L to define adequacy outside of and during pregnancy, respectively. Iodine creatinine ratio (ICR) is also used to correct for dilution effects (sufficiency ≥150 µg/g creatinine in pregnancy).

DESIGN AND METHODS

A total of 241 women were followed across trimesters (T) into the postpartum period (PPP) along with 80 offspring with spot urine sampling and food frequency questionnaires.

RESULTS

Median UIC was 73 µg/L in the 1st T (ICR 102 µg/g creatinine) despite 55% taking iodine-containing supplements. Median UICs were 94, 117 and 90 µg/L in the 2nd T, 3rd T and PPP, respectively. Corresponding ICRs were 120, 126 and 60 µg/g creatinine. ICR was associated with volume of milk consumed throughout pregnancy. Median UIC among the offspring was 148 µg/L, with no difference between the breast- and formula-fed babies.

CONCLUSIONS

Pregnant women living in Northern Ireland may be at risk of iodine deficiency across pregnancy and into the PPP while the offspring are iodine sufficient. This is the first study of its kind in the UK with data for pregnant women and their offspring. The UK does not provide an iodine fortification programme nor offer routine iodine dietary advice in pregnancy and this requires consideration by public health agencies.

What is the availability of iodised salt in supermarkets on the Island of Ireland?

Iodine deficiency remains a global nutritional public health challenge, with evidence suggesting borderline adequate or even deficient status for UK and Irish subpopulations such as schoolgirls and pregnant women. The solution, according to the WHO, is salt iodisation, but it is not known how widely available iodised salt is in supermarkets. Iodised salt availability was determined by a shelf survey of 89 supermarket stores on the island of Ireland (n = 30 in Northern Ireland and n = 59 in the Republic of Ireland) from September 2018 to January 2019, to take into account factors such as store type, location, population density, socioeconomic status and ethnicity. Availability was calculated as the number of stores selling iodised salt as a percentage of the total. Iodised salt was only available in 11 stores (12%), of which 10 were ethnic stores. This indicates a lack of access for the majority of the Irish and Northern Irish populations.

Agreement between markers of population iodine status in classifying iodine status of populations: a systematic review

BACKGROUND

Population iodine deficiency is indicated by >3% of the population with newborn thyroid-stimulating hormone (TSH) concentration >5 mIU/L, median urinary iodine concentration (MUIC) <100 µg/L, or >5% prevalence of goiter in school-age children. However, the agreement between these population markers has not been systematically investigated.

OBJECTIVE

To assess the agreement between TSH, MUIC, and goiter as markers of population iodine status.

METHODS

We performed a systematic search for studies published on PubMed, Scopus, Cumulative Index to Nursing and Allied Health Literature (CINAHL), Embase, and PsycINFO up to 29 October, 2018. Studies assessing iodine status in the population using the TSH marker and either MUIC or goiter prevalence in school-age children were included. The agreement between markers in classifying iodine status of the population was assessed. The sensitivity and specificity of the TSH marker was determined against MUIC and goiter prevalence as the reference markers.

RESULTS

Of 17,435 records identified by the search strategy, 57 eligible studies were included in the review. The agreement between markers in classifying the iodine status of populations into the same category was 65% for TSH and MUIC, and 83% for TSH and goiter prevalence. The TSH marker had a sensitivity of 0.75 and specificity of 0.53 when compared with MUIC, and 0.86 and 0.50 when compared with goiter prevalence.

CONCLUSIONS

The TSH marker has a better agreement with goiter prevalence than MUIC when classifying the iodine status of populations. Re-evaluation of the current criteria for classifying the iodine status of populations using the TSH marker is warranted. This systematic review was registered at PROSPERO (http://www.crd.york.ac.uk/prospero/) as CRD42018091247.

Micronutrients, iodine status and concentrations of thyroid hormones: a systematic review

Context

The metabolism of thyroid hormones, which are essential for normal development, involves many proteins and enzymes. It requires iodine as a key component but is also influenced by several other micronutrients, including selenium, zinc, iron, and vitamin A.

Objective

This systematic review was designed to investigate the effect of micronutrient status and supplementation on iodine status and thyroid hormone concentrations.

Data Sources

Using the PRISMA (Preferred Reporting Items for Systematic Reviews and Meta-Analysis) guidelines, electronic databases were searched from their inception to April 2016.

Study Selection

Human studies published in English and reporting data on micronutrient status and iodine status and/or thyroid hormone concentrations were included. Studies that examined the effect of micronutrient supplementation on iodine status and/or thyroid hormone concentrations were also included.

Data Extraction

A predesigned and piloted data extraction form was used to compile data from individual studies.

Results

A total of 57 studies were included: 20 intervention studies and 37 observational studies. Although observational evidence suggests that concentrations of selenium, zinc, and iron are positively associated with iodine status, data from randomized controlled trials fail to confirm this relationship.

Conclusions

Further studies are needed to provide greater understanding of the role of micronutrient status in iodine nutrition and thyroid function to ascertain the public health implications for populations worldwide.

DUOX2/DUOXA2 Mutations Frequently Cause Congenital Hypothyroidism that Evades Detection on Newborn Screening in the United Kingdom

Background: The etiology, course, and most appropriate management of borderline congenital hypothyroidism (CH) are poorly defined, such that the optimal threshold for diagnosis with bloodspot screening thyrotropin (bsTSH) measurement remains controversial. Dual oxidase 2 (DUOX2) mutations may initially cause borderline elevation of bsTSH, which later evolves into significant hypothyroidism on venous blood measurement. It was hypothesized that mutations in both DUOX2 and its accessory protein DUOXA2 may occur frequently, even in patients with borderline bsTSH elevation, such that higher diagnostic thresholds in bsTSH screening may fail to detect such cases, with consequent risk of undiagnosed neonatal hypothyroidism of sufficient magnitude to require thyroxine therapy. This study aimed to investigate the frequency and characteristics of DUOX2 and DUOXA2 mutations in a borderline CH cohort. Methods: A cross-sectional study of patients with borderline CH was undertaken at Great Ormond Street Hospital, a tertiary British pediatric center. DUOX2 was sequenced in 52 patients with a bsTSH of 6-19.9 mIU/L, venous TSH of >25 mIU/L, and eutopic thyroid gland in situ. DUOXA2 was sequenced in DUOX2 mutation-negative cases, and novel DUOXA2 mutations were functionally characterized. Results: A total of 26 (50%) patients harbored likely pathogenic mutations in DUOX2 (n = 20; 38%) or DUOXA2 (n = 6; 12%), including novel gene variants (DUOX2, n = 3; DUOXA2, n = 7). Two recurrent DUOX2 mutations (p.Q570L, p.F966Sfs*29) occurred frequently in population databases (MAF ≥0.01). Despite bsTSH being <10 mIU/L in 46% of DUOX2 and DUOXA2 mutation-positive cases, venous free thyroxine levels in these patients were in the moderate CH range (M = 9.3 pmol/L, range <3.9-15.8 pmol/L), Conclusions: Targeted DUOX2 and DUOXA2 sequencing in a borderline CH cohort has a high diagnostic yield. These findings might argue for a lowering of bsTSH thresholds, but follow-up studies are required to assess whether cases with borderline bsTSH harboring DUOX2/DUOXA2 mutations will benefit from an early diagnosis and subsequent levothyroxine treatment.

Iodine status of reproductive age women and their toddlers in northern Ghana improved through household supply of iodized salt and weekly indigenous meal consumption

Iodine deficiency (ID) during pregnancy results in pregnancy losses, intrauterine growth retardation, and lower IQ in the offspring. Even after two decades of universal salt iodization (USI) implementation, the efficacy of USI has not been reported in high risk groups in vulnerable regions in Ghana. We aimed to assess and improve ID status in childbearing age women (all lactating women) and their toddlers in northern Ghana, a geographically and socioeconomically vulnerable region. We provided weekly supply of household iodized salt and community-based feeding of native Hibiscus Sabdariffaa leaves meal (HSM) prepared with iodized salt to women and their toddlers in intervention (n = 60) vs. control group (n = 60). At baseline, ID was prevalent in women (36%) and their toddlers (29%). For women, both median UIC values for intervention (57.4 ug/l) and control group (65.1 ug/l) were below the recommended UIC value of 100 ug/l with no significant differences between the two groups (p = 0.2778). At the endpoint, median UIC for the intervention group (123.6 ug/l) was significantly higher (p = 0.008) than the control group (59.7 ug/l). Our results suggest that weekly supply of iodized salt along with the feeding HSM is an effective channel for improving iodine status of economically disadvantaged groups in communities remote from coastal lands. Furthermore, our results suggest that decreased median UIC among lactating mothers does not necessarily imply lower iodine status for their breastfed toddlers. And finally, the observed median UIC<100 ug/l may point to a non-improvement in iodine status for the past decade for Ghana. There is a need to revisit, assess, and ascertain the challenges in preventing populations from attaining the intended benefits of the USI policy in Ghana.

Knowledge about iodine requirements during pregnancy and breastfeeding among pregnant women living in Northern Ireland

Background

Iodine is an essential micronutrient important for foetal nerve and brain development, especially in the early stages of pregnancy. The re-emergence of mild to moderate iodine deficiency has recently been reported in the United Kingdom (UK). The level of knowledge amongst pregnant women regarding iodine nutrition is poorly understood. The aim of this study was to determine the level of knowledge about iodine nutrition during pregnancy among pregnant women living in Northern Ireland (NI).

Methods

A cross-sectional study in pregnant women was carried out in Royal Jubilee Maternity Hospital Belfast, from March to June 2015. Two hundred pregnant women were provided with a short questionnaire on iodine knowledge during routine clinic visits and comparisons were made across trimester and parity.

Results

Only 20% of women were aware of the potentially increased iodine requirements during pregnancy and breast feeding; 45% were unable to identify any foods they thought would be iodine rich. The three main sources of dietary iodine in the UK are fish, dairy and eggs and 30, 9 and 15% correctly identified these as good sources respectively. When asked about whether they felt they had been given sufficient advice about folic acid and iodine in pregnancy, 90% felt this was so for folic acid, but only 5% for iodine.

Conclusions

This study suggests that iodine knowledge among pregnant women living in NI is poor. In the absence of any iodine fortification programme, women in the UK may be vulnerable to iodine deficiency in pregnancy. At present they are poorly equipped to make positive dietary changes to meet their increasing iodine requirements during pregnancy and breastfeeding. Public health strategies should be considered to target this population group.

Iodine fortification of foods and condiments, other than salt, for preventing iodine deficiency disorders

BACKGROUND

Iodine deficiency disorders (IDD) affect close to 1.9 billion people worldwide, and are a major public health concern in many countries. Among children, iodine deficiency is the main cause of potentially preventable deficits of central nervous system development and impairment of cognitive function, as well as goitre and hypothyroidism in people of all ages. Salt iodisation is the preferred strategy for IDD prevention and control, however, in some instances where salt is not the major condiment, alternate vehicles for iodine fortification have been considered.

OBJECTIVES

To assess the effects of fortifying foods, beverages, condiments, or seasonings other than salt with iodine alone or in conjunction with other micronutrients, on iodine status and health-related outcomes in all populations.

SEARCH METHODS

Studies were identified through systematic searches of the following databases from their start date to January 2018: Cochrane Public Health Group Specialised Register; CENTRAL; MEDLINE; MEDLINE in Process; Embase; Web of Science; CINAHL; POPLINE; AGRICOLA; BIOSIS; Food Science and Technology Abstracts; OpenGrey; Bibliomap and TRoPHI; AGRIS; IBECS; Scielo; Global Index Medicus-AFRO and EMRO; LILACS; PAHO; WHOLIS; WPRO; IMSEAR; IndMED; and Native Health Research Database. We also searched reference list of relevant articles, conference proceedings, and databases of ongoing trials, and contacted experts and relevant organisations to identify any unpublished work. We applied no language or date restrictions.

SELECTION CRITERIA

Studies were eligible if they were randomised or quasi-randomised controlled trials (RCT) with randomisation at either the individual or cluster level (including cross-over trials), non-randomised RCTs, or prospective observational studies with a control group, such as cohort studies, controlled before-and-after studies, and interrupted time series. We included studies that examined the effects of fortification of food, beverage, condiment, or seasoning with iodine alone, or in combination with other micronutrients versus the same unfortified food, or no intervention. We considered the following measures: death (all-cause), goitre, physical development, mental development, cognitive function and motor skill development, cretinism, hypothyroidism, adverse effects (any reported by trialists), urinary iodine concentration, thyroid-stimulating hormone (TSH) concentration, and serum thyroglobulin concentration. We included all populations, including pregnant women, from any country.

DATA COLLECTION AND ANALYSIS

Two review authors independently assessed study eligibility, extracted data, and assessed risk of bias of included studies.We used random-effects meta-analyses to combine data and generate an overall estimate of treatment effect, when more than one study examined the same outcome measure. The overall effect estimate was calculated as the mean difference (MD) or standardised mean difference (SMD) between the intervention group and the comparison group for continuous outcomes, and as odds ratio (OR) for dichotomous outcomes. We assessed the level of heterogeneity through the I² statistic. We conducted post-hoc subgroup analyses to explore possible sources of heterogeneity, and sensitivity analyses to check the robustness of the findings from the primary analyses. We assessed the quality of the evidence for each outcome using the GRADE framework.Where it was not possible to pool the results in a meta-analysis, we provided a narrative summary of the outcomes.

MAIN RESULTS

Eleven studies met the criteria, providing 14 comparisons, and capturing data on 4317 participants. Seven studies were RCTs, three were cluster non-RCTs, and one was a randomised cross-over design. Seven studies were carried out among school children (N = 3636), three among women of reproductive age (N = 648), and one among infants (N = 33). The studies used diverse types of food as vehicle for iodine delivery: biscuits, milk, fish sauce, drinking water, yoghourt, fruit beverage, seasoning powder, and infant formula milk. Daily amounts of iodine provided ranged from 35 µg/day to 220 µg/day; trial duration ranged from 11 days to 48 weeks. Five studies examined the effect of iodine fortification alone, two against the same unfortified food, and three against no intervention. Six studies evaluated the effect of cofortification of iodine with other micronutrients versus the same food without iodine but with different levels of other micronutrients. We assessed one study to be at low risk of bias for all bias domains, three at low risk of bias for all domains apart from selective reporting, and seven at an overall rating of high risk of bias.No study assessed the primary outcomes of death, mental development, cognitive function, cretinism, or hypothyroidism, or secondary outcomes of TSH or serum thyroglobulin concentration. Two studies reported the effects on goitre, one on physical development measures, and one on adverse effects. All studies assessed urinary iodine concentration.The effects of iodine fortification compared to control on goitre prevalence (OR 1.60, 95% CI 0.60 to 4.31; 1 non-RCT, 83 participants; very low-quality evidence), and five physical development measures were uncertain (1 non-RCT, 83 participants; very low-quality evidence): weight (MD 0.23 kg, 95% CI -6.30 to 6.77); height (MD -0.66 cm, 95% CI -4.64 to 3.33); weight-for-age (MD 0.05, 95% CI -0.59 to 0.69); height-for-age (MD -0.30, 95% CI -0.75 to 0.15); and weight-for-height (MD -0.21, 95% CI -0.51 to 0.10). One study reported that there were no adverse events observed during the cross-over trial (low-quality evidence).Pooled results from RCTs showed that urinary iodine concentration significantly increased following iodine fortification (SMD 0.59, 95% CI 0.37 to 0.81; 6 RCTs, 2032 participants; moderate-quality evidence). This is equivalent to an increase of 38.32 µg/L (95% CI 24.03 to 52.61 µg/L). This effect was not observed in the meta-analysis of non-RCTs (SMD 0.25, 95% CI -0.16 to 0.66; 3 non-RCTs, 262 participants; very low-quality evidence). Sensitivity analyses did not change the effect observed in the primary analyses.

AUTHORS' CONCLUSIONS

The evidence on the effect of iodine fortification of foods, beverages, condiments, or seasonings other than salt on reducing goitre, improving physical development measures, and any adverse effects is uncertain. However, our findings suggest that the intervention likely increases urinary iodine concentration. Additional, adequately powered, high-quality studies on the effects of iodine fortification of foods on these, and other important outcomes, as well as its efficacy and safety, are required.

Trends, Determinants, and Associations of Treated Hypothyroidism in the United Kingdom, 2005-2014

BACKGROUND

Recent reports suggest that prescriptions for thyroid hormones have increased. Recent trends in and determinants of the prevalence of treated hypothyroidism across the United Kingdom were therefore analyzed.

METHODS

Data covering the whole of the United Kingdom held by the National Health Service and the Office of National Statistics were examined. The main outcome measured was trends in the prevalence of treated hypothyroidism between 2005 and 2014. In addition, linear trend forecasting was performed to estimate projected trends in the prevalence of treated hypothyroidism up to the year 2025. Furthermore, determinants of variation of treated hypothyroidism prevalence across each of the 237 health areas in the United Kingdom in 2014 and its association with other health conditions were explored by multivariate linear regression analyses.

RESULTS

The prevalence of treated hypothyroidism increased from 2.3% (1.4 million) to 3.5% (2.2 million) of the total British population between the years 2005 and 2014 and is projected to rise further to 4.2% (2.9 million) by 2025. There was large geographical variation of treated hypothyroidism across the United Kingdom, with London having the lowest (1.4%) and the Western Isles of Scotland having the highest (6.3%) prevalence. This variation was attenuated, but did not completely disappear, after some potential determinants were accounted for. The prevalence of treated hypothyroidism was independently related to health areas, with a higher proportion of individuals who were female, white, and obese, and negatively associated with prevalent cigarette smoking. The prevalence of treated hypothyroidism was significantly associated with the frequency of prevalent atrial fibrillation but not with other major health conditions, including ischemic heart disease and osteoporosis.

CONCLUSIONS

Between 2005 and 2014, the prevalence of treated hypothyroidism increased across the United Kingdom, has wide geographical variation, and is likely to increase further for the foreseeable future. Clinical effects and cost-effectiveness of the trend in increasing treatment of hypothyroidism remains to be evaluated.

Iodine status, and knowledge about iodine deficiency disorders in adolescent school girls aged 14-19 years, 2016

Background: Adequate iodine intake by women in child-bearing age affects fetus neurodevelopment during pregnancy. A majority of previous studies has investigated iodine status among children, and there is limited data on female adolescents who are more exposed to consequences of iodine deficiency (ID) in their near-future pregnancies; thus, we aimed to assess iodine status, and knowledge on iodine deficiency disorders (IDDs) among adolescent school girls (14-19 years old) in Shahriar, Iran. Methods: This cross-sectional study was conducted among 223 female students selected through multi-stage cluster sampling from 12 schools. Iodine and creatinine concentrations were measured in casual urine samples. Iodine content of household salts was also assessed.Data on intake of salt and iodine-rich food sources were collected applying a food frequency questionnaire (FFQ), and knowledge about iodine and IDDs were assessed by a questionnaire. Results: Median and Mean (95% CI) concentrations of urinary iodine and creatinine were 129 µg/L, 137.62 µg/L (95% CI: 126.28, 148.95) and 1.72 g/L, 1.86 g/L (95% CI: 0.55-3.17),respectively. The frequency of mild, moderate and severe ID were 22.4%, 14.3% and 0%,respectively; 43.5% had adequate, and 3.1% had excessive urinary iodine levels. Mean saltiodine concentration was 21.69 (SD=10.56) ppm. Mean knowledge score was 12.7 (SD=3.44).About half of the students had a poor (25.1%) or fair (24.2%) knowledge about iodine deficiency.Adjusting for the confounders, no significant positive association was found between knowledge about iodine-rich food sources and goitrogens with urinary iodine excretion. Conclusion: Adolescent girls in Shahriar had relatively poor knowledge of iodine, and about one third of them suffered from ID.

Delayed conception in women with low-urinary iodine concentrations: a population-based prospective cohort study

STUDY QUESTION

Is iodine deficiency associated with decreased fecundability?

SUMMARY ANSWER

Moderate to severe iodine deficiency is associated with a 46% decrease in fecundability.

WHAT IS KNOWN ALREADY

Iodine deficiency is common in women of childbearing age but its effect on fecundability has not been investigated.

STUDY DESIGN, SIZE, DURATION

The LIFE Study, a population-based prospective cohort study, enrolled 501 women who had discontinued contraception within 2 months to become pregnant between 2005 and 2009.

PARTICIPANTS/MATERIALS, SETTING, METHODS

Women reported on risk factors for infertility by interview then kept daily journals of relevant information. Women used fertility monitors to time intercourse relative to ovulation then used home digital pregnancy tests to identify pregnancies on the day of expected menstruation. Urine samples for iodine analysis were collected on enrollment.

MAIN RESULTS AND THE ROLE OF CHANCE

Samples were in the deficiency range in 44.3% of participants. The group whose iodine-creatinine ratios were below 50 μg/g (moderate to severe deficiency) had a 46% reduction in fecundity (P = 0.028) compared with the group whose iodine-creatinine ratios were in the adequate range: adjusted fecundability odds ratio of becoming pregnant per cycle, 0.54 (95% confidence interval 0.31-0.94).

LIMITATIONS, REASONS FOR CAUTION

Iodine concentrations vary within individuals over time, so the data must be interpreted by group as we have done; residual confounding is possible.

WIDER IMPLICATIONS OF THE FINDINGS

Significant delays in becoming pregnant occur at iodine concentrations that are common in women in the USA and parts of Europe. Replicating these findings will be important to determine whether improving iodine status could be beneficial in improving fecundability.

STUDY FUNDING/COMPETING INTEREST(S)

This study was funded by the Intramural Research Program, Eunice Kennedy Shriver National Institute of Child Health and Human Development, National Institutes of Health, USA. Contracts N01-HD-3-3355; N01-HD-3-3356; N01-HD-3-3358 and HHSN275201100001l/HHSN27500007. None of the authors has any conflict of interest to declare.

A Comparative Study of Iodized Salt Programs: Shanghai and Switzerland

Both Shanghai and Switzerland are developed regions with long-standing salt iodization programs and periodic monitoring. However, the two regions have their own approach to the implementation of the iodized salt policy. In Shanghai, monitoring was carried out every few years, using probability-proportional-to-size sampling technique to select 30 sampling units. Each unit consisted of more than 12 pregnant women and one randomly selected primary school. Urine samples were then taken from the chosen pregnant women and randomly recruited students of that school for iodine test. Data of Switzerland used in this comparative study was extracted from published researches. In Shanghai, the median urinary iodine concentration (UIC) in 2014 was 20% lower than in 1999 (P < 0.05). The median UIC of pregnant women in 2014 was 9.5% lower than that in 2011 (P < 0.05). In terms of iodized salt concentration, opposite to the increasing in Switzerland, it has exhibited a downward trend in Shanghai (P < 0.05). For the years monitored, the iodized salt concentration in Shanghai was significantly (P < 0.05) higher than in Switzerland. Though the UIC of children exhibited a downward trend in Shanghai (P < 0.05), it was still significantly (P < 0.05) higher than in Switzerland over the same monitoring period. However, the UIC in pregnant women was a totally different story, which was significantly (P < 0.05) lower in Shanghai than in Switzerland. Iodized salt is very important for maintaining sufficient iodine level in the population. Appropriate concentration of iodine in fortified salt needs to be decided according to local conditions. Special attention should be paid to the iodine level of pregnant women in Shanghai, and more education about iodine is necessary for the public health.

A systematic review of iodine deficiency among women in the UK

OBJECTIVE

The present study reviewed the literature on iodine status among women of childbearing age and pregnant women in the UK. Particular attention was given to study quality and methods used to assess iodine status.

DESIGN

A systematic review was conducted to examine the literature and critically evaluate study design.

SETTING

Studies were identified in PubMed, Web of Science, Scopus and Ovid MEDLINE databases, as well as from secondary references.

PARTICIPANTS

Women of childbearing age or pregnant, living in the UK.

RESULTS

Fifty-seven articles were identified and twelve articles were selected, including a total of 5283 women. Nine studies conducted urinary iodine assessments, three studies conducted dietary assessments only, and seven studies classified their target population as iodine deficient according to WHO criteria.

CONCLUSIONS

No single study from the selected articles could produce nationally representative results regarding the prevalence of iodine deficiency among the female population in the UK. Consideration of the evidence as a whole suggests that women of childbearing age and pregnant women in the UK are generally iodine insufficient. Further large-scale research is required for more accurate and reliable evidence on iodine status in the UK.

DIAGNOSIS OF ENDOCRINE DISEASE: Congenital hypothyroidism: update and perspectives

Congenital hypothyroidism (CH) may be primary, due to a defect affecting the thyroid gland itself, or central, due to impaired thyroid-stimulating hormone (TSH)-mediated stimulation of the thyroid gland as a result of hypothalamic or pituitary pathology. Primary CH is the most common neonatal endocrine disorder, traditionally subdivided into thyroid dysgenesis (TD), referring to a spectrum of thyroid developmental abnormalities, and dyshormonogenesis, where a defective molecular pathway for thyroid hormonogenesis results in failure of hormone production by a structurally intact gland. Delayed treatment of neonatal hypothyroidism may result in profound neurodevelopmental delay; therefore, CH is screened for in developed countries to facilitate prompt diagnosis. Central congenital hypothyroidism (CCH) is a rarer entity which may occur in isolation, or (more frequently) in association with additional pituitary hormone deficits. CCH is most commonly defined biochemically by failure of appropriate TSH elevation despite subnormal thyroid hormone levels and will therefore evade diagnosis in primary, TSH-based CH-screening programmes. This review will discuss recent genetic aetiological advances in CH and summarize epidemiological data and clinical diagnostic challenges, focussing on primary CH and isolated CCH.