Iodine status of pregnant women living in urban Johannesburg, South Africa.

Adequate intake of iodine is important during pregnancy because of its essential role in foetal growth and neurodevelopment. Data on iodine status of South African pregnant women are scarce, and the salt reduction policy implemented in 2016 may decrease iodine intake of South Africans. This cross-sectional study assessed the iodine status of pregnant women residing in urban Johannesburg, South Africa. A total of 250 pregnant women were enrolled into the 'Nutrition during Pregnancy and Early Development' (NuPED) study and 312 pregnant women into the 'Assessment of dried blood spot thyroglobulin in pregnant women to redefine the range of median urinary iodine concentration that indicates adequate iodine intake, South Africa' (STRIPE-SA) study and were included in this analysis. Urinary iodine concentration (UIC) was analysed in a spot urine sample. Thyroglobulin (Tg) was measured in serum, and thyroid-stimulating hormone (TSH) and total thyroxine (tT4) were measured in dried blood spots. The median [interquartile range (IQR)] UIC of pregnant women was 144 (84-234) µg/L. Women in the first (n = 99), second (n = 262) and third (n = 174) trimester had a median UIC of 133 (81-316), 145 (84-236) and 156 (89-245) µg/L, respectively (p = 0.419). Median TSH, tT4 and Tg were 2.7 (2.3-3.2) mU/L, 202 (163-236) nmol/L and 9.2 (5.4-17.9) µg/L, respectively. Based on the median UIC, pregnant women residing in urban Johannesburg may be borderline iodine deficient. These findings highlight the need for ongoing monitoring of iodine status among vulnerable pregnant women, especially considering the recently introduced salt reduction policy in South Africa.

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.

Breast milk and erythrocyte fatty acid composition of lactating women residing in a peri­urban 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 peri­urban township. The mean age of the lactating women was 27.8 ±â€¯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 peri­urban 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.