Urinary Iodine, Perchlorate, and Thiocyanate Concentrations in U.S. Lactating Women.

BACKGROUND: Iodine is an essential micronutrient for thyroid hormone production. Adequate iodine intake and normal thyroid function are important during early development, and breastfed infants rely on maternal iodine excreted in breast milk for their iodine nutrition. The proportion of women in the United States of childbearing age with urinary iodine concentration (UIC) <50 µg/L has been increasing, and a subset of lactating women may have inadequate iodine intake. UIC may also be influenced by environmental exposure to perchlorate and thiocyanate, competitive inhibitors of iodine transport into thyroid, and lactating mammary glands. Data regarding UIC in U.S. lactating women are limited. To adequately assess the iodine sufficiency of lactating women and potential associations with environmental perchlorate and thiocyanate exposure, we conducted a multicenter, cross-sectional study of urinary iodine, perchlorate, and thiocyanate concentrations in healthy U.S. lactating women. METHODS: Lactating women ≥18 years of age were recruited from three U.S. geographic regions: California, Massachusetts, and Ohio/Illinois from November 2008 to June 2016. Demographic information and multivitamin supplements use were obtained. Iodine, perchlorate, and thiocyanate levels were measured from spot urine samples. Correlations between urinary iodine, perchlorate, and thiocyanate levels were determined using Spearman's rank correlation. Multivariable regression models were used to assess predictors of urinary iodine, perchlorate, and thiocyanate levels, and UIC <100 µg/L. RESULTS: A total of 376 subjects (≥125 from each geographic region) were included in the final analyses [mean (SD) age 31.1 (5.6) years, 37% white, 31% black, and 11% Hispanic]. Seventy-seven percent used multivitamin supplements, 5% reported active cigarette smoking, and 45% were exclusively breastfeeding. Median urinary iodine, perchlorate, and thiocyanate concentrations were 143 µg/L, 3.1 µg/L, and 514 µg/L, respectively. One-third of women had UIC <100 µg/L. Spot urinary iodine, perchlorate, and thiocyanate levels all significantly positively correlated to each other. No significant predictors of UIC, UIC <100 µg/L, or urinary perchlorate levels were identified. Smoking, race/ethnicity, and marital status were significant predictors of urinary thiocyanate levels. CONCLUSION: Lactating women in three U.S. geographic regions are iodine sufficient with an overall median UIC of 143 µg/L. Given ubiquitous exposure to perchlorate and thiocyanate, adequate iodine nutrition should be emphasized, along with consideration to decrease these exposures in lactating women to protect developing infants.

Maternal iodine status during lactation and infant weight and length in Henan Province, China.

BACKGROUND: Infants are very sensitive to iodine deficiency. Breastfed infants are dependent on maternal iodine intake. The aim of this study was to evaluate the relationship between maternal iodine status during lactation and infant weight and length. METHODS: A cross-sectional survey was conducted to investigate maternal iodine status and infant anthropometric measures in Henan Province, China. Only exclusive breastfeeding mothers and their infants < 6 months of age (n = 747) were included in our final analysis. Urine samples were collected from all the mothers and infants. Infant weight and length were measured and converted into weight-for-age Z-score (WAZ) and height-for-age Z-score (HAZ) using the World Health Organization (WHO) AnthroPlus software. RESULTS: The median urinary iodine concentration (UIC) in lactating women was significant lower than that in their infants (177.4 vs 261.1 µg/L, P < 0.001). A positive correlation was found between maternal and infant urinary iodine concentration (r = 0.203, P < 0.01). The mean HAZ and WAZ values were lowest in the infants whose mothers had UIC below 50 µg/L (n = 41). Infant WAZ with maternal UIC below 50 µg/L was significantly lower than those with maternal UIC of 50 µg/L or above (P = 0.043). After adjusting for confounding factors, there were significant differences in infant WAZ between maternal UIC groups. CONCLUSIONS: The present study suggests that maternal iodine status during lactation may be related to their infant anthropometric index. Appropriate iodine intake of lactating women is beneficial for their infants.

Choline intakes exceeding recommendations during human lactation improve breast milk choline content by increasing PEMT pathway metabolites.

Demand for the vital nutrient choline is high during lactation; however, few studies have examined choline metabolism and requirements in this reproductive state. The present study sought to discern the effects of lactation and varied choline intake on maternal biomarkers of choline metabolism and breast milk choline content. Lactating (n=28) and control (n=21) women were randomized to 480 or 930 mg choline/day for 10-12 weeks as part of a controlled feeding study. During the last 4-6 weeks, 20% of the total choline intake was provided as an isotopically labeled choline tracer (methyl-d9-choline). Blood, urine and breast milk samples were collected for choline metabolite quantification, enrichment measurements, and gene expression analysis of choline metabolic genes. Lactating (vs. control) women exhibited higher (P < .001) plasma choline concentrations but lower (P ≤ .002) urinary excretion of choline metabolites, decreased use of choline as a methyl donor (e.g., lower enrichment of d6-dimethylglycine, P ≤ .08) and lower (P ≤ .02) leukocyte expression of most choline-metabolizing genes. A higher choline intake during lactation differentially influenced breast milk d9- vs. d3-choline metabolite enrichment. Increases (P ≤ .03) were detected among the d3-metabolites, which are generated endogenously via the hepatic phosphatidylethanolamine N-methyltransferase (PEMT), but not among the d9-metabolites generated from intact exogenous choline. These data suggest that lactation induces metabolic adaptations that increase the supply of intact choline to the mammary epithelium, and that extra maternal choline enhances breast milk choline content by increasing supply of PEMT-derived choline metabolites. This trial was registered at clinicaltrials.gov as NCT01127022.

Folate-status response to a controlled folate intake in nonpregnant, pregnant, and lactating women.

BACKGROUND: Folate dose-response studies in women of childbearing age who consumed a folic acid (FA)-containing multivitamin in the era of FA fortification are lacking. OBJECTIVE: We sought to investigate folate-status response to a known folate dose comprising an FA-containing prenatal supplement (750 µg/d) plus natural food folate (400 µg/d) in third-trimester pregnant women, lactating women 5-15 wk postpartum, and nonpregnant women. DESIGN: Pregnant (n = 26), lactating (n = 28), and nonpregnant (n = 21) women consumed the study folate dose under controlled intake conditions for 10-12 wk. Blood, urine, and breast milk were collected at baseline, study midpoint, and study end. RESULTS: Study-end serum total folate concentrations averaged ~30 ng/mL and did not differ by physiologic group (P = 0.876). Study-end urinary folate excretion represented ~9-43% of total folate intake and ranged from 100 to 500 µg/d. Third-trimester pregnant women excreted less urinary folate than did lactating (P = 0.075) and nonpregnant (P < 0.001) women. Lactating women excreted less (P < 0.001) urinary FA than did nonpregnant women. Breast-milk total folate concentrations remained constant (P = 0.244; 61.8 ng/mL at study end), whereas breast-milk FA concentrations increased (P = 0.003) to 24.1 ng/mL at study end. CONCLUSIONS: The consumption of the study folate dose yielded a supranutritional folate status regardless of the physiologic state. Based on urinary folate excretion, folate use was greatest to least: pregnant > lactating > nonpregnant women. Breast-milk folate species were responsive to maternal folate intake, and FA made up ~40% of breast-milk total folate at study end. These findings warrant revisiting prenatal supplement FA formulation in populations exposed to FA-fortification programs.

Iodine status and thyroid function of pregnant, lactating women and infants (0-1 yr) residing in areas with an effective Universal Salt Iodization program.

OBJECTIVE: To assess the iodine nutrition and thyroid function of pregnant women, lactating women and infants residing in areas where the Universal Salt Iodization program is in place. METHODS: Pregnant women, lactating women and infants were selected randomly in the regions where iodized salt coverage rate is more than 90% since 2000. Urine iodine levels of pregnant woman, lactating woman and infants, milk iodine of lactating woman, thyroid-stimulating hormone (TSH) and free T4 of women were tested respectively. RESULTS: Median Urinary Iodine (MUI) of infants, three groups of pregnant women (first, second and third trimester) and two groups lactating women (breastfeeding less than or more than six months) were 233, 174, 180, 147, 126 and 145 microg/L, respectively. Median milk iodine of lactating women was 163 microg/L. Percentage of milk iodine < 150 microg/L of early lactating women was 40% less than that of late lactating women (p < 0.01).There was a positive correlation between urine iodine of infants and milk iodine of lactating women (r = 0.526, p = 0.000). T4 of two women were above or below the reference range. Total 15.4% women's TSH were abnormal. Most of these women's urinary iodine were lower than 150 microg/L. CONCLUSION: Iodine status of most of the target population for Universal Salt Iodization program is adequate, but iodine deficiency still existed in some. To assure every new life's brain not be damaged by iodine deficiency, iodine status of targeted populations should be monitored and supplements provided according to the monitoring outcomes.

Seasonal variation in selenium status of different classes of grazing goats in a semi-arid region of Pakistan.

The selenium status of three different classes of goats ((i) female lactating, (ii) female non-lactating, and (iii) male goats) grazing semi-arid pasture in the southern part of the Punjab province, Pakistan and that of selenium concentration of soil and dietary sources, ingested by those animals were investigated during two different seasons of the year (winter and summer). Soil, forage, feed, water from the pasture and blood plasma, urine, faeces, and (if applicable) milk from these goats were collected fortnightly. The samples were analyzed for selenium concentrations. Soil selenium showed both seasonal and sampling periods effect on its concentration while forage selenium was affected only by the seasonal changes. No significant effect of seasons or fortnights on feed selenium level was observed. In fecal samples selenium concentration in lactating and non-lactating and plasma of male goats were affected by sampling periods. While fecal selenium in male goats showed significant effect on its concentration both seasonal and within fortnights. Severe deficient level of soil selenium during both seasons and marginal deficient level of forage selenium during summer were observed. Selenium concentrations in feed slightly exceeded the requirements of ruminants in feed during both seasons of the year. Plasma selenium concentrations in all goat classes were higher in winter than that in summer showing no seasonal or fortnight variation and its concentration was slightly lower in lactating goats as compared to other classes. On the bases of these results, it is concluded that overall selenium status of the goats based on plasma selenium concentration may be considered adequate mainly due to the mineral supplement provided all over the year, since soil and forage selenium concentrations were low to deficient.

Assessment and recommendations on factors contributing to preanalytical variability of urinary pyridinoline and deoxypyridinoline.

BACKGROUND: Pyridinoline (PYD) and deoxypyridinoline (DPD) are two of the most extensively characterized biochemical bone markers, but the interpretation of results is hampered by biologic and other preanalytical variability. We reviewed factors contributing to preanalytical variation of pyridinium cross-links in urine. METHODS: We searched four databases for English-language reports on PYD and/or DPD in urine. Searches were restricted to humans, except for studies of stability, when the search was expanded to other species. The 599 identified articles were supplemented with references from those articles and with articles known to the authors. RESULTS: The mean reported within-day variability was 71% for PYD (range, 57-78%) and 67% for DPD (range, 53-75%). The mean interday variability was 16% for both DPD and PYD (range for PYD, 12-21%; range for DPD, 5-24%). The mean intersubject variabilities across studies were 26% for PYD (range, 12-63%) and 34% for DPD (range, 8-98%) for healthy premenopausal women and 36% (range, 22-61%) and 40%, (range, 27-54%) for postmenopausal women, respectively. Specimen instability and errors in creatinine measurements were additional sources of variability. CONCLUSIONS: Intra- and intersubject variability can be reduced by collecting specimens at a specific time of the day and by maintaining similar patient status at each specimen collection regarding factors such as medications and dietary supplements.

Urinary selenium and iodine during pregnancy and lactation.

The New Zealand environment is low in selenium and iodine, and is therefore ideally suited for the study of these anionic trace elements. The aim of this study was to determine urinary excretion of selenium and iodine during pregnancy and postpartum as part of an investigation of the influence of pregnancy and lactation on selenium metabolism in women of low selenium status. In a double-blind placebo-controlled study, 35 women in the earliest stages of pregnancy and 17 non-pregnant women were recruited in Dunedin, New Zealand. Eighteen pregnant women received 50 microg selenium as L-selenomethionine, while the others received a placebo daily during pregnancy and 12 months postpartum. The non-pregnant women received the supplement, serving as a positive control. Blood samples and twenty-four hour urine samples were collected monthly during pregnancy and at 3, 6, and 12 months postpartum for analysis of selenium and iodine. Selenium content in plasma and urinary excretion of selenium fell during pregnancy; however, total excretion of selenium was greater during pregnancy than postpartum. Urinary iodine excretion was much lower than reported previously in New Zealand. Due to large intra- and inter-subject variability, no trends in iodide excretion were observed. Factors which influence urinary excretion of selenium include dietary intake, but more closely, plasma concentrations of selenium (which is probably related to total selenium pool), creatinine excretion and therefore lean body mass, and glomerular filtration rate. The exact mechanism and sequence of events remains unclear and future studies incorporating new speciation techniques are necessary.

Biochemical markers of calcium and bone metabolism during 18 months of lactation in Gambian women accustomed to a low calcium intake and in those consuming a calcium supplement.

The effect of 18 months of lactation on indexes of calcium and bone metabolism was studied in 60 Gambian women accustomed to a very low calcium intake. Half the women consumed a calcium supplement from 10 days postpartum for 52 weeks (supplement, 714 mg Ca/day; total Ca intake, 992 +/- 114 mg/day), and half consumed placebo (total Ca intake, 288 +/- 128 mg/day). Fasting blood and 24-h urine samples were collected at 1.5, 13, 52, and 78 weeks of lactation and analyzed for calciotropic hormones (intact PTH, 1,25-dihydroxyvitamin D, and calcitonin), bone turnover markers (osteocalcin, bone alkaline phosphatase, and urinary deoxypyridinoline), and plasma minerals (calcium and phosphate). The first months of lactation were associated with increased bone turnover and plasma phosphate, and decreased PTH and 1,25-dihydroxyvitamin D. These effects diminished by 52 weeks, although breast milk volumes remained high. The Gambians had higher PTH, 1,25-dihydroxyvitamin D, and bone formation than British women with a greater customary calcium intake. None of the biochemical indexes was affected by calcium supplementation, with the possible exception of bone alkaline phosphatase (-29% at 52 weeks; P = 0.015). These data demonstrate that lactation-associated changes in calcium and bone metabolism are physiological and are independent of dietary calcium supply in women with very low calcium intakes.

Urinary iodine level as an intake indicator in dairy cows.

Urinary iodine concentrations were determined in 672 dairy cows of 22 herds. Less than 20 micrograms per L, 20 to 50 micrograms per L, 50 to 100 micrograms per L and more than 100 micrograms per L were found in 27.5, 24.6, 16.8, and 31.3% of the cows, respectively. In terms of the ICCIDD grading, moderate iodine deficiency was recorded in 68.9% and normal iodine intake in 31.3% of the cows. The mean urinary iodine concentrations were 94.8 micrograms per L at the peak of the lactation period (n = 300), 82.3 micrograms per L immediately before drying off (n = 122), 92.5 micrograms per L in the cows fed summer rations (n = 267), and 79.2 micrograms per L in those fed winter rations (n = 405). The differences in mean values were nonsignificant. Urinary iodine concentrations were examined in the herd LOS in cows fed iodine-supplemented (LOS E) or nonsupplemented (LOS C) rations. Mean concentrations were 316.2 micrograms per L for LOS E (n = 46) and 52.3 micrograms per L for LOS C (n = 41). The difference was highly significant (P < 0.01). The status of the group LOS C was classified as a medium iodine deficiency. The mean iodine concentrations at the peak of the lactation period and immediately before drying off were also significantly higher (P < 0.01) in this group. The supplementation of iodine resulted in an increase of urinary iodine concentration and, in terms of ICCIDD, the increase of iodine intake to the normal range. Normal intake and moderate, medium and serious deficits were found in three, two, one, and four herds, respectively. Special attention should be paid to herds showing higher grades of iodine deficiency.

Trace mineral metabolism in non-gravid, gestating and lactating gilts fed two dietary levels of manganese.

Six pairs of littermate Landrace gilts weighing 100-110 kg were randomly assigned to one of the experimental diets; 1) Low Mn: basal corn-soya diet (10 mg/kg) or 2) High Mn: basal+supplement (84 mg/kg), and maintained in individual stainless steel metabolic cages. Consumption of the semipurified diet was restricted to 2.5 kg/d with water available at all times ad libitum. Retention of Mn, Cu, Zn, and Fe were determined using the balance technique in the non-gravid state and at 30, 60 and 100 days of gestation. Blood samples were collected at the initiation of each balance period, the day before farrowing and at the end of lactation. Colostrum and milk were collected at birth and one week after farrowing, respectively. Piglets were bled at birth and weaning. Significant differences in mineral retention were not detected between the two dietary treatments. Retention of Mn was not influenced by pregnancy and averaged 1.37 +/- 0.92 mg/d and 0.97 +/- 0.92 mg/d for the supplemented and basal treatments, respectively. Fecal Zn excretion declined (P less than 0.01) at 100 days of gestation in both treatment groups and thus tended to improve Zn retention. Plasma Mn did not reflect Mn intake, but was significantly reduced at 100 days of gestation from the non-gravid state. Colostrum and milk from supplemented dams tended to contain higher concentrations of Mn. Total litter weight at birth was significantly greater for supplemented gilts.