Breast-Milk Iodine Concentrations, Iodine Status, and Thyroid Function of Breastfed Infants Aged 2-4 Months and Their Mothers Residing in a South African Township

Do Postpartum Maternal Iodine Status or Supplementation Affect Thyroid Function After Delivery? A Systematic Review and Meta-Analysis

The aim of this systematic review and meta-analysis was, for the first time, to explore whether postpartum maternal iodine status or supplementation is associated with thyroid function after delivery. The MEDLINE/PubMed, Web of Science, Embase, and Scopus were searched up to December 2021 to identify relevant studies. The pooled mean thyroid stimulating hormone (TSH), free thyroxine (fT4), and thyroxine (T4) concentrations and 95% confidence intervals (CIs) were estimated based on maternal urinary iodine concentration (UIC) (< 50, 50-100, 100-200, and > 200 µg/L) or breast milk iodine concentration (BMIC) (< 100 µg/L vs. ≥ 100 µg/L) during postpartum. A fixed/random effects model was used based on the absence/presence of heterogeneity, respectively. The study is registered with PROSPERO, number CRD42022336145. A total of 2175 studies were identified, of which 18 were eligible for the meta-analysis. The pooled values for TSH, fT4, and T4 concentrations in all subgroups were within the normal range; however, except for TSH, comparing the 95% CI showed no statistically significant difference among different subgroups. The pooled mean for TSH concentration in women with UIC > 200 µg/L was 2.23 mIU/L, whereas the corresponding values in women with UIC < 50, 50-100 and 100-200 µg/L were 0.56, 0.56 and 0.95 mIU/L, respectively. Thyroid hormones in women with BMIC < 100 µg/L and ≥ 100 µg/L were within the normal range. Iodine supplementation during postpartum was not associated with any differences in thyroid parameters, compared to non-supplemented women. In conclusion, iodine status or supplementation had no effect on thyroid hormones in postpartum women.

Iodine Nutrition in Children ≤2 years of Age in Norway

BACKGROUND

As a component of the thyroid hormones (THs), iodine is vital for normal neurodevelopment during early life. However, both deficient and excess iodine may affect TH production, and data on iodine status in young children are scarce.

OBJECTIVES

To describe iodine nutrition (iodine status and intake) in children ≤2 y of age in Innlandet County (Norway) and to describe the associations with maternal iodine nutrition.

METHODS

A cross-sectional study was performed in a representative sample of mother-child pairs selected from 30 municipalities from November 2020 until October 2021. Iodine status [child urinary iodine concentration (UIC), maternal UIC, and breast milk iodine concentration (BMIC)] was measured. Child's iodine intake was estimated using 2 24-h dietary recalls (24-HR) and a food frequency questionnaire. The Multiple Source Method was used to estimate the usual iodine intake distributions from the 24-HR assessments.

RESULTS

The median UIC in 333 children was 145 μg/L, indicating adequate iodine status according to the WHO cutoff (100 μg/L). The median usual iodine intake was 83 μg/d. Furthermore, 35% had suboptimal usual iodine intakes [below the proposed Estimated average requirement (72 μg/d)], whereas <1% had excessive usual iodine intakes [above the Upper intake level (200 μg/d)]. There was a positive correlation between children's iodine intake and BMIC (Spearman rank correlation coefficient r = 0.67, P < 0.001), and between children's UIC and BMIC (r = 0.43, P < 0.001), maternal UIC (r = 0.23, P = 0.001), and maternal iodine intake (r = 0.20, P = 0.004).

CONCLUSION

Despite a median UIC above the cutoff for iodine sufficiency, more than a third of the children had suboptimal usual iodine intakes. Our findings suggest that many children will benefit from iodine fortification and that risk of iodine excess in this age group is low.

Iodine Concentration in the Breast Milk and Urine as Biomarkers of Iodine Nutritional Status of Lactating Women and Breastfed Infants in Taiwan

Breast milk iodine concentration (BMIC) can be different when median urinary iodine concentration (UIC) is similar. The BMIC, UIC/creatinine (Cr), estimated 24-h urinary iodine excretion (24-h UIE) of lactating women in Taiwan is unknown. This study enrolled lactating women from Taipei Veterans General Hospital (August 2021-February 2023). Each participant provided a random spot urine sample, two breast milk samples, a blood sample, and completed a food frequency questionnaire on the same day. Iodine measurement was performed by inductively coupled plasma mass spectrometry. The median UIC of the enrolled 71 women was 91.1 μg/L, indicating insufficient iodine status; however, the median BMIC was 166.6 μg/L and this suggested that the amount of iodine delivered through breast milk was adequate for the breastfed infants. BMIC was correlated with UIC/Cr and 24-h UIE (both rs = 0.49) but not with UIC (rs = 0.18) or thyroid stimulating hormone (rs = 0.07). Women who did not consume dairy products (adjusted odds ratio: 24.41, 95% confidence interval: 1.26-471.2) and multivitamins (adjusted odds ratio: 8.26, 95% confidence interval: 1.76-38.79) were at increased odds for having lower BMIC. The results suggest that measuring maternal UIC alone may not be sufficient, as BMIC, UIC/Cr, and 24-h UIE are all important biomarkers. Ingestion of dairy products and multivitamins were independently associated with BMIC.

Infant iodine status and associations with maternal iodine nutrition, breast-feeding status and thyroid function

Adequate iodine nutrition during infancy is required for normal thyroid function and, subsequently, brain development. However, data on infant iodine status in the first year of life are scarce. This study aimed to describe infant iodine status and further explore its associations with maternal iodine nutrition, breast-feeding status and thyroid function. In this cohort study, 113 infants were followed up at ages 3, 6 and 11 months in Norway. Infant and maternal urinary iodine concentration (UIC), maternal iodine intake, breast milk iodine concentration (BMIC), breast-feeding status and infant thyroid function tests were measured. The median infant UIC was 82 µg/l at the age of 3 months and below the WHO cut-off of 100 µg/l. Infant UIC was adequate later in infancy (median 110 µg/l at ages 6 and 11 months). Infant UIC was associated positively with maternal UIC (β = 0·33, 95 % CI (0·12, 0·54)), maternal iodine intake (β = 0·30, 95 % CI (0·18, 0·42)) and BMIC (β = 0·46, 95 % CI (0·13, 0·79)). Breastfed infants had lower median UIC compared with formula-fed infants at ages 3 months (76 v. 190 µg/l) and 6 months (105 v. 315 µg/l). Neither infant UIC nor BMIC were associated with infant thyroid function tests. In conclusion, breastfed infants in Norway are at risk of insufficient iodine intake during the first months of life. Maternal iodine nutrition is important for providing sufficient iodine intake in infants, and awareness of promoting adequate iodine nutrition for lactating women should be prioritised.

The Role of Iodine for Thyroid Function in Lactating Women and Infants

Iodine is a micronutrient needed for the production of thyroid hormones, which regulate metabolism, growth, and development. Iodine deficiency or excess may alter the thyroid hormone synthesis. The potential effects on infant development depend on the degree, timing, and duration of exposure. The iodine requirement is particularly high during infancy because of elevated thyroid hormone turnover. Breastfed infants rely on iodine provided by human milk, but the iodine concentration in breast milk is determined by the maternal iodine intake. Diets in many countries cannot provide sufficient iodine, and deficiency is prevented by iodine fortification of salt. However, the coverage of iodized salt varies between countries. Epidemiological data suggest large differences in the iodine intake in lactating women, infants, and toddlers worldwide, ranging from deficient to excessive intake. In this review, we provide an overview of the current knowledge and recent advances in the understanding of iodine nutrition and its association with thyroid function in lactating women, infants, and toddlers. We discuss risk factors for iodine malnutrition and the impact of targeted intervention strategies on these vulnerable population groups. We highlight the importance of appropriate definitions of optimal iodine nutrition and the need for more data assessing the risk of mild iodine deficiency for thyroid disorders during the first 2 years in life.

Breast Milk Iodine Concentration (BMIC) as a Biomarker of Iodine Status in Lactating Women and Children <2 Years of Age: A Systematic Review

Background: Iodine is needed for the production of thyroid hormones, which are essential for infant growth and development. Given that there are wide variations in breast milk iodine concentration (BMIC) and urinary iodine concentration (UIC), it is unclear if BMIC is associated with UIC in populations residing in iodine sufficient or deficient areas. Aim: To investigate if BMIC can be used as a biomarker for iodine status in lactating women and children <2 years of age. Methods: Electronic databases; PubMed, Web of Science and Scopus were searched until year 2021, for studies investigating the relationship between BMIC and UIC. Studies were reviewed for eligibility, according to inclusion and exclusion criteria, followed by data extraction, according to the PRISMA guidelines. Results: Overall, 51 studies met the criteria for inclusion in the systematic review. BMIC ranged from 18 to 1153 µg/L. In iodine-deficient and iodine-sufficient lactating women, BMIC ranged from 26 to 185 µg/L and 15 to 1006 µg/L, respectively. In most studies, the categorisation of iodine status assessed by median UIC was consistent with the categorisation of iodine status assessed by median BMIC cut off of ≥100 µg/L, to determine iodine sufficiency in lactating women and children <2 years of age. Conclusions: The systematic review indicated that BMIC is a promising biomarker of iodine status in lactating women and children <2 years of age. However, these data need to be interpreted cautiously, given the study limitations in the included studies. Future studies should consider investigating the optimal median BMIC, as there is a lack of high-quality observational and intervention studies in lactating women and infants.

Characterization of Genetic Variants in the SLC5A5 Gene and Associations With Breast Milk Iodine Concentration in Lactating Women of African Descent: The NUPED Study

Background: The sodium iodide symporter is responsible for the transfer of iodine into breast milk and is encoded for by the SLC5A5 gene. The role of genetic variants in the SLC5A5 gene locus in relation to the transfer of iodine from plasma into breast milk in healthy lactating individuals has, to our knowledge, not been explored. Objective: To identify and characterize possible genetic variants of the SLC5A5 gene in women of African descent living in urban South Africa, and to study associations with breast milk iodine concentrations (BMIC) in lactating women. Methods: This study is affiliated to the Nutrition during Pregnancy and Early Development (NuPED) cohort study (n = 250 enrolled pregnant women). In a randomly selected sub-sample of 32 women, the SLC5A5 gene was sequenced to identify known and novel variants. Of the identified variants, genotyping of selected variants was performed in all pregnant women who gave consent for genetic analyses (n = 246), to determine the frequency of the variants in the study sample. Urinary iodine concentration (UIC) in spot urine samples and BMIC were measured to determine iodine status. Associations of SLC5A5 genetic variants with BMIC were studied in lactating women (n = 55). Results: We identified 27 variants from sequencing of gene exomes and 10 variants were selected for further study. There was a significant difference in BMIC between the genotypes of the rs775249401 variant (P = 0.042), with the homozygous GG group having lower BMIC [86.8 (54.9-167.9) μg/L] compared to the (A) allele carriers rs775249401(AG+AA) [143.9 (122.4-169.3) μg/L] (P = 0.042). Of the rs775249401(GG), 49% had UIC <100 μg/L and 61% had BMIC <100 μg/L. On the other hand, 60% of the rs775249401(AG+AA) carriers had UIC <100 μg/L, and none had a BMIC <100 μg/L. Conclusion: Our results suggest that A-allele carriers of rs775249401(AG+AA) are likely to have higher iodine transfer into breast milk compared to the homozygous GG counterparts. Thus, genetic variations in the SLC5A5 gene may play an important role in the transfer of iodine from plasma into breast milk and may partially explain inter-individual variability in BMIC.

Salt Used for the National School Nutrition Program (NSNP) in Rural Schools of Limpopo Province, South Africa, has Adequate Levels of Iodine

Background

Salt iodisation is considered the most effective long-term public health intervention for achieving optimal iodine nutrition. Effective salt iodisation is a prerequisite for the sustainable elimination of iodine deficiency disorders. The aim of this study was to determine iodine concentration of salt used for the National School Nutrition Program (NSNP).

Methods

A cross-sectional study was conducted in 359 food handlers from Vhembe and Mopani districts of Limpopo Province, South Africa. The questionnaire was administered to solicit data on demographic information, general questions on salt fortification, and iodine nutrition knowledge. After the interviews, two tablespoons of salt used for the NSNP food preparation was collected from 318 schools in small zip-lock plastic bags. The salt samples were coded and stored at room temperature and protected from light and moisture until the time of analysis. Salt iodine concentrations were determined at the North-West University (NWU) in Potchefstroom by means of the iCheck test method.

Results

The median iodine concentration of both Mopani (31.65 ppm) and Vhembe (32.56 ppm) districts signified adequate iodine levels. Of 318 salt samples, 113 (71%) samples in Mopani and 104 (65%) in Vhembe had an iodine concentration of 15-64 ppm. A few (6%) food handlers in Mopani and almost half (45.9%) in Vhembe could correctly identify iodated salt as the main source of iodine. Almost half of the food handlers (%) in Mopani and 36.5% in Vhembe did not know which part of body needs iodine for functioning.

Conclusion

More than 20 years after the implementation of the USI program, the result of the study shows that the international goal of 90% coverage is still far from being realised.

Iodine status during pregnancy and at 6 weeks, 6, 12 and 18 months post-partum

Iodine deficiency during pregnancy and in the post‐partum period may lead to impaired child development. Our aim is to describe iodine status longitudinally in women from pregnancy until 18 months post‐partum. Furthermore, we explore whether iodine status is associated with dietary intake, iodine‐containing supplement use and breastfeeding status from pregnancy until 18 months post‐partum. We also assess the correlation between maternal iodine status 18 months post‐partum and child iodine status at 18 months of age. Iodine status was measured by urinary iodine concentration (UIC) during pregnancy (n = 1,004), 6 weeks post‐partum (n = 915), 6 months post‐partum (n = 849), 12 months post‐partum (n = 733) and 18 months post‐partum (n = 714). The toddlers' UIC was assessed at 18 months of age (n = 416). Demographic variables and dietary data (food frequency questionnaire) were collected during pregnancy, and dietary data and breastfeeding practices were collected at all time points post‐partum. We found that iodine status was insufficient in both pregnant and post‐partum women. The UIC was at its lowermost 6 weeks post‐partum and gradually improved with increasing time post‐partum. Intake of milk and use of iodine‐containing supplements significantly increased the odds of having a UIC above 100 μg/L. Neither the mothers' UIC, vegetarian practice, nor exclusion of milk and dairy products were associated with the toddlers UIC 18 months post‐partum. Women who exclude milk and dairy products from their diets and/or do not use iodine‐containing supplements may be at risk of iodine deficiency. The women possibly also have an increased risk of thyroid dysfunction and for conceiving children with nonoptimal developmental status.

Interference on Iodine Uptake and Human Thyroid Function by Perchlorate-Contaminated Water and Food

Background: Perchlorate-induced natrium-iodide symporter (NIS) interference is a well-recognized thyroid disrupting mechanism. It is unclear, however, whether a chronic low-dose exposure to perchlorate delivered by food and drinks may cause thyroid dysfunction in the long term. Thus, the aim of this review was to overview and summarize literature results in order to clarify this issue. Methods: Authors searched PubMed/MEDLINE, Scopus, Web of Science, institutional websites and Google until April 2020 for relevant information about the fundamental mechanism of the thyroid NIS interference induced by orally consumed perchlorate compounds and its clinical consequences. Results: Food and drinking water should be considered relevant sources of perchlorate. Despite some controversies, cross-sectional studies demonstrated that perchlorate exposure affects thyroid hormone synthesis in infants, adolescents and adults, particularly in the case of underlying thyroid diseases and iodine insufficiency. An exaggerated exposure to perchlorate during pregnancy leads to a worse neurocognitive and behavioral development outcome in infants, regardless of maternal thyroid hormone levels. Discussion and conclusion: The effects of a chronic low-dose perchlorate exposure on thyroid homeostasis remain still unclear, leading to concerns especially for highly sensitive patients. Specific studies are needed to clarify this issue, aiming to better define strategies of detection and prevention.

Breast milk and erythrocyte fatty acid composition of lactating women residing in a peri‑urban South African township

Data on breast milk fatty acid (FA) composition in South African lactating women in relation to their FA status, as well as on potential compositional changes within feed, are limited. The aim of this study was to assess the FA composition of breast milk sampled at three time points within feed, and to determine associations with red blood cell (RBC) total phospholipid FA levels in lactating South African mothers of 2-4-month-old breastfed infants. FA composition (% total FAs) was analyzed in RBC total phospholipids, and in fore-, mid-feed and hind-milk samples of lactating mothers (n = 100) of Black African descent living in a peri‑urban township. The mean age of the lactating women was 27.8 ± 6.8 years. Geometric mean (95% CI) breast milk SFA, MUFA and PUFA contents were 37.7 (37.3,38.1), 28.5 (27.9, 28.8), and 23.5 (23.2, 24.5)%, respectively. Breast milk DHA and AA contents were 0.25 (0.24, 3.71) and 0.81 (0.79, 0.83)%, respectively, in fore-, mid- and hind-milk combined. Maternal RBC EPA, DHA and AA levels were 0.37 (0.34, 0.40), 3.8 (3.6, 4.0) and 15.4 (14.8, 16.1)%, respectively. Women who reported to consume fish often (n = 3) had significantly higher RBC EPA levels than women who consumed fish sometimes (n = 56), never (n = 14) or rarely (n = 19). Breast milk DHA positively correlated with maternal RBC DHA, while no correlations were found between breast milk AA and maternal RBC AA. Breast milk ALA and DHA contents were significantly higher in mid-feed [ALA= 0.8 (0.2, 0.2), DHA=0.3 (0.2, 0.3)] and hind-milk [ALA=0.8 (0.8, 0.9), DHA=0.3 (0.3, 0.3)] than foremilk [ALA=0.8 (0.7, 0.9), DHA=0.2 (0.2, 0.3)]. In contrast, LA and AA contents remained constant within feed. In this sample of peri‑urban South African lactating mothers, breast milk was low in DHA and high in AA compared to global means. Breast milk DHA was associated with maternal RBC status, while breast milk AA was not. We further showed that breast milk ALA and DHA increased, while LA and AA remained unchanged within feed. This suggests that n-3 PUFA maybe preferentially transferred to breast milk within feed through biomagnification.

Iodine status of breastfed infants and their mothers' breast milk iodine concentration

Iodine is an essential nutrient for growth and development during infancy. Data on iodine status of exclusively (EBF) and partially breastfed (PBF) infants as well as breast milk iodine concentration (BMIC) are scarce. We aimed to assess (a) infant iodine nutrition at the age of 5.5 months by measuring urinary iodine concentration (UIC) in EBF (n = 32) and PBF (n = 28) infants and (b) mothers' breast milk iodine concentration (n = 57). Sixty mother–infant pairs from three primary health care centres in Reykjavik and vicinities provided urine and breast milk samples for iodine analysis and information on mothers' habitual diet. The mother–infant pairs were participants of the IceAge2 study, which focuses on factors contributing to infant growth and development, including body composition and breast‐milk energy content. The median (25th–75th percentiles) UIC was 152 (79–239) μg/L, with no significant difference between EBF and PBF infants. The estimated median iodine intake ranged from 52 to 86 μg/day, based on urinary data (assuming an average urine volume of 300–500 ml/day and UIC from the present study). The median (25th–75th percentiles) BMIC was 84 (48–114) μg/L. It is difficult to conclude whether iodine status is adequate in the present study, as no ranges for median UIC reflecting optimal iodine nutrition exist for infants. However, the results add important information to the relatively sparse literature on UIC, BMIC, and iodine intake of breastfed infants.

Mild to Moderate Iodine Deficiency and Inadequate Iodine Intake in Lactating Women in the Inland Area of Norway

Breastfed infants are dependent on an adequate supply of iodine in human milk for the production of thyroid hormones, necessary for development of the brain. Despite the importance of iodine for infant health, data on Norwegian lactating women are scarce. We measured iodine intake and evaluated iodine status and iodine knowledge among lactating women. From October to December 2018, 133 mother–infant pairs were recruited in a cross-sectional study through two public health care centers in Lillehammer and Gjøvik. Each of the women provided two human milk specimens, which were pooled, and one urine sample for analysis of iodine concentration. We used 24-h dietary recall and food frequency questionnaire (FFQ) to estimate short-term and habitual iodine intake from food and supplements. The median (P25, P75) human milk iodine concentration (HMIC) was 71 (45, 127) µg/L—of which, 66% had HMIC <100 µg/L. The median (P25, P75) urinary iodine concentration (UIC) was 80 µg/L (52, 141). The mean (± SD) 24-h iodine intake and habitual intake was 78 ± 79 µg/day and 75 ± 73 µg/day, respectively. In conclusion, this study confirms inadequate iodine intake and insufficient iodine status among lactating women in the inland area of Norway and medium knowledge awareness about iodine.

Breast Milk Iodine Concentration Is Associated with Infant Growth, Independent of Maternal Weight

In breastfed infants, human milk provides the primary source of iodine to meet demands during this vulnerable period of growth and development. Iodine is a key micronutrient that plays an essential role in hormone synthesis. Despite the importance of iodine, there is limited understanding of the maternal factors that influence milk iodine content and how milk iodine intake during infancy is related to postnatal growth. We examined breast milk samples from near 2 weeks and 2 months post-partum in a mother-infant dyad cohort of mothers with pre-pregnancy weight status defined by body mass index (BMI). Normal (NW, BMI < 25.0 kg/m2) is compared to overweight/obesity (OW/OB, BMI ≥ 25.0 kg/m2). The milk iodine concentration was determined by inductively coupled plasma mass spectrometry. We evaluated the associations between iodine content at 2 weeks and infant anthropometrics over the first year of life using multivariable linear mixed modeling. Iodine concentrations generally decreased from 2 weeks to 2 months. We observed no significant difference in iodine based on maternal weight. A higher iodine concentration at 2 weeks was associated with a larger increase in infant weight-for-age and weight-for-length Z-score change per month from 2 weeks to 1 year. This pilot study shows that early iodine intake may influence infant growth trajectory independent of maternal pre-pregnancy weight status.

Excess iodine intake: sources, assessment, and effects on thyroid function

Iodine is essential for thyroid hormone synthesis. High iodine intakes are well tolerated by most healthy individuals, but in some people, excess iodine intakes may precipitate hyperthyroidism, hypothyroidism, goiter, and/or thyroid autoimmunity. Individuals with preexisting thyroid disease or those previously exposed to iodine deficiency may be more susceptible to thyroid disorders due to an increase in iodine intake, in some cases at intakes only slightly above physiological needs. Thyroid dysfunction due to excess iodine intake is usually mild and transient, but iodine-induced hyperthyroidism can be life-threatening in some individuals. At the population level, excess iodine intakes may arise from consumption of overiodized salt, drinking water, animal milk rich in iodine, certain seaweeds, iodine-containing dietary supplements, and from a combination of these sources. The median urinary iodine concentration (UIC) of a population reflects the total iodine intake from all sources and can accurately identify populations with excessive iodine intakes. Our review describes the association between excess iodine intake and thyroid function. We outline potential sources of excess iodine intake and the physiological responses and consequences of excess iodine intakes. We provide guidance on choice of biomarkers to assess iodine intake, with an emphasis on the UIC and thyroglobulin.

High Urinary Iodine Concentration Among Breastfed Infants and the Factors Associated with Iodine Content in Breast Milk

Iodine deficiency in infants leads to delayed growth and development. Some studies have reported iodine deficiency among infants and lactating women. We assessed iodine status in infants and lactating women, as well as the iodine content in breast milk. A cross-sectional study enrolled mother-infant pairs (infants aged 4-6 months), who visited Well Child Clinic at Ramathibodi Hospital, Bangkok, Thailand. Infants were classified by feeding type as breastfed (BF), mixed breastfed and formula-fed (MF), and formula-fed (FF). Demographic and perinatal data were collected. The urinary iodine concentration (UIC) of infants and lactating women, and breast milk iodine concentration (BMIC) were analyzed. Seventy-one infants were enrolled. The median UIC of infants was 282 mcg/L. Breastfed infants had higher median UIC than formula-fed infants (553 vs. 192 mcg/L; p = 0.002). Forty-eight percent of infants had a UIC more than 300 mcg/L. The median UIC and BMIC of lactating women were 149 and 255 mcg/L, respectively. Among the BF group, the infant UIC was correlated with maternal UIC (r_s = 0.857, p = 0.014). Multiple linear regression showed the BMIC to be associated with maternal UIC (β = 4.03, 95% CI [1.34, 6.71]) and maternal weight (β = 8.26, 95%CI [2.76, 13.77]). Iodine nutrition among our study population was adequate. The median UIC of infants and lactating mothers were 282 and 149 mcg/L, respectively. Breastfed infants had a significantly higher median UIC than formula-fed infants. The BMIC was associated with maternal UIC and maternal weight.

Nutrition during pregnancy and early development (NuPED) in urban South Africa: a study protocol for a prospective cohort

BACKGROUND

Adequate nutrition during pregnancy is important to ensure optimal birth outcomes, maternal health and offspring development. However, little is known about the dietary intake and nutritional status of pregnant women residing in urban South Africa. Therefore, the Nutrition during Pregnancy and Early Development (NuPED) cohort study was initiated to assess early nutrition-related exposures predictive of early childhood development in urban South Africa.

METHODS

The aims of this prospective cohort study are: 1) to assess dietary intake and nutritional status of urban pregnant women in Johannesburg, South Africa, and 2) to determine associations with birth outcomes, measures of maternal health, as well as measures of offspring health and development. Pregnant women (< 18 weeks' gestation) (n = 250) are being recruited from primary healthcare clinics in Johannesburg and are followed-up at a provincial hospital. Participants' dietary intake and nutrient status (focus on micronutrients and fatty acids) are assessed at < 18, 22 and 36 weeks' gestation. Additional assessments during pregnancy include anthropometric and blood pressure measurements, obstetric ultrasound screens, and assessments of food security, maternal fatigue, prenatal depression, allergy, immune function, morbidity and gestational diabetes. At birth, maternal and neonatal health is assessed and an umbilical cord blood sample collected. Maternal and offspring health is followed-up at 6 weeks, as well as at 6, ≈7.5 and 12 months after birth. Follow-up assessments of mothers include anthropometric measures, diet history, nutrient status, blood pressure, breast milk composition, and measures of postnatal depression and fatigue. Follow-up assessments of the offspring include feeding practices, nutrient status, measures of growth, psychomotor, socio-emotional and immune development, morbidity, allergy, as well as analysis of the gut microbiome and the epigenome.

DISCUSSION

Ensuring adequate nutrition during pregnancy is one of the key actions endorsed by the South African Government to promote optimal early childhood development in an effort to eradicate poverty. The results from this study may serve as a basis for the development of context-specific nutritional interventions which can improve birth outcomes and long-term quality of life of the mother and her offspring.

Iodine Status Assessment in South African Adults According to Spot Urinary Iodine Concentrations, Prediction Equations, and Measured 24-h Iodine Excretion

The iodine status of populations is conventionally assessed using spot urinary samples to obtain a median urinary iodine concentration (UIC) value, which is assessed against standard reference cut-offs. The assumption that spot UIC reflects daily iodine intake may be flawed because of high day-to-day variability and variable urinary volume outputs. This study aimed to compare iodine status in a sample of South African adults when determined by different approaches using a spot urine sample (median UIC (MUIC), predicted 24 h urinary iodine excretion (PrUIE) using different prediction equations) against measured 24 h urinary iodine excretion (mUIE). Both 24 h and spot urine samples were collected in a subsample of participants (n = 457; median age 55 year; range 18⁻90 year) in the World Health Organization Study on global AGEing and adult health (SAGE) Wave 2 in South Africa, in 2015. Kawasaki, Tanaka, and Mage equations were applied to assess PrUIE from predicted urinary creatinine (PrCr) and spot UIC values. Adequacy of iodine intake was assessed by comparing PrUIE and mUIE to the Estimated Average Requirement of 95 µg/day, while the MUIC cut-off was.

Interrelationship between iodine nutritional status of lactating mothers and their absolutely breast-fed infants in coastal districts of Gangetic West Bengal in India

Iodine nutritional status of 128 lactating mothers and their breast-fed infants (1-3 months) from iodine-replete villages during post-salt iodization period was evaluated. Mothers' urine, blood, and breast milk (BM) and infants' urine and blood were collected and analyzed for iodine and serum FT₄ and TSH estimation. Mothers' and infants' age, parity, occupation, education, and household income were recorded. Median urinary iodine concentration (UIC) of infants was 250 μg/L, indicating their iodine intake was more than adequate. Mothers' median UIC was 185 μg/L, indicating adequate iodine nutrition; however, 13.28% had mild to severe deficiency. Median breast milk iodine concentration (BMIC) was 230 μg/L, which was more than their median UIC 185 μg/L. In iodine-deficient mothers, positive correlation was found between mothers' and infants' serum FT₄ and TSH levels, and negative correlation was found between mothers' and infants' serum FT₄ and TSH levels in excessive iodine nutrition group.

CONCLUSION

Iodine intake of breast-fed infants was at the limit of above requirement, and they are possibly at the risk of excess iodine intake. In iodine deficient and excessive iodine intake mothers, their infants' serum FT₄ and TSH are independent on their iodine nutritional status but dependent on thyroid hormone profile of their mothers but differently. What is Known: • A median urinary iodine of 100 μg/L is used to define adequate iodine intake of lactating mothers and children < 2 years. However, adequate iodine intake in terms of urinary iodine of infants of age 1-3 months is not known. What is New: • Iodine intake of absolutely breast-fed infants (1-3 months) was more than adequate, though their mother's intake was adequate as breast milk contains more iodine than urine. The infants of iodine deficient and excessive iodine intake mothers, infants' hormonal profile is independent of their iodine nutritional status but dependent on their mothers thyroid hormone profile.

Human Milk and Allergic Diseases: An Unsolved Puzzle

There is conflicting evidence on the protective role of breastfeeding in relation to the development of allergic sensitisation and allergic disease. Studies vary in methodology and definition of outcomes, which lead to considerable heterogeneity. Human milk composition varies both within and between individuals, which may partially explain conflicting data. It is known that human milk composition is very complex and contains variable levels of immune active molecules, oligosaccharides, metabolites, vitamins and other nutrients and microbial content. Existing evidence suggests that modulation of human breast milk composition has potential for preventing allergic diseases in early life. In this review, we discuss associations between breastfeeding/human milk composition and allergy development.

Suboptimal Iodine Concentration in Breastmilk and Inadequate Iodine Intake among Lactating Women in Norway

Breastfed infants depend on sufficient maternal iodine intake for optimal growth and neurological development. Despite this, few studies have assessed iodine concentrations in human milk and there is currently no published data on iodine status among lactating women in Norway. The aim of this study was to assess iodine concentrations in breast milk (BMIC) in lactating women and estimate iodine intake. Five Mother and Child Health Centres in Oslo were randomly selected during 2016, and 175 lactating women between 2nd and 28th weeks postpartum participated. Each of the women provided four breastmilk samples which were pooled and analysed for iodine concentrations. Participants also provided information on iodine intake from food and supplements covering the last 24 h and the habitual iodine intake (food frequency questionnaire). The median (p25, p75 percentiles) BMIC was 68 (45, 98) µg/L and 76% had BMIC <100 µg/L. Only 19% had taken an iodine-containing supplement during the last 24 h. The median 24 h iodine intake from food (p25, p75) was 121 (82, 162) µg/day and the total intake (food and supplements) was 134 (95, 222) µg/day. The majority of lactating women had suboptimal BMIC and inadequate intake of iodine from food and supplements.

Iodine status and associations with feeding practices and psychomotor milestone development in six-month-old South African infants

Iodine is important for normal growth and psychomotor development. While infants below 6 months of age receive iodine from breast milk or fortified infant formula, the introduction of complementary foods poses a serious risk for deteriorating iodine status. This cross-sectional analysis assessed the iodine status of six-month-old South African infants and explored its associations with feeding practices and psychomotor milestone development. Iodine concentrations were measured in infant (n = 386) and maternal (n = 371) urine (urinary iodine concentration [UIC]), and in breast milk (n = 257 [breast milk iodine concentrations]). Feeding practices and psychomotor milestone development were assessed in all infants. The median (25th-75th percentile) UIC in infants was 345 (213-596) μg/L and was significantly lower in stunted (302 [195-504] μg/L) than non-stunted (366 [225-641] μg/L) infants. Only 6.7% of infants were deficient. Maternal UIC (128 [81-216] μg/L; r_s  = 0.218, p < 0.001) and breast milk iodine concentrations (170 [110-270] μg/kg; r_s  = 0.447, p < 0.0001) were associated with infant UIC. Most infants (72%) were breastfed and tended to have higher UIC than non-breastfed infants (p = 0.074). Almost all infants (95%) consumed semi-solid or solid foods, with commercial infant cereals (60%) and jarred infant foods (20%) being the most common solid foods first introduced. Infants who reported to consume commercial infant cereals ≥4 days weekly had significantly higher UIC (372 [225-637] μg/L) than those reported to consume commercial infant cereals seldom or never (308 [200-517] μg/L; p = 0.023). No associations between infant UIC and psychomotor developmental scores were observed. Our results suggest that iodine intake in the studied six-month-old infants was adequate. Iodine in breast milk and commercial infant cereals potentially contributed to this adequate intake.