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Iodine and the Body

 

Pregnancy

 

Dorea

 

Maternal exposure to endocrine-active substances and breastfeeding.

Dorea JG.

Am J Perinatol. 2006 Jul;23(5):305-12. Epub 2006 Jun 23

[abstract only]

 

"Women pass on low levels of hazardous environmental contaminants and naturally occurring substances during pregnancy and nursing. In addition to estrogenic activity, these substances exhibit antiestrogenic, antiandrogenic, and androgenic actions, and because they can affect thyroid metabolism, they are described as endocrine-active substances (EAS). Specific topics related to EAS metabolism by mothers, fetuses, and infants are discussed. There is strong evidence that the assumed risk of EAS in early human development is exacerbated by interrupting neonatal priming provided by breastfeeding. The benefits of breastfeeding are fundamental to attenuate possible EAS effects on infants due to long-term intrauterine exposure. Breastfeeding is a guarantor of health benefits, whereas its alternative (infant formula) is a predictor of some health limitations. Mothers concerned with exposure to environmental contaminants should be advised of the proven benefits of breastfeeding and the possible health limitations of formula feeding."

 

 

Early (in uterus and infant) exposure to mercury and lead.

Dorea JG, Donangelo CM.

Clin Nutr. 2006 Jun;25(3):369-76. Epub 2005 Nov 22.

[abstract only]

 

"Mercury and lead are toxic metals widely spread in the environment with bio-accumulative features that raises public health concerns. Both metals are equally dispersed in the human food chain but exposure and risk of toxicity during early human development are modulated by the diet and nutritional status. Understanding how Hg and Pb occur and interact with nutrients is fundamental to establish guidelines for diminishing exposure and the risk of toxicity. The risk of fetal and infant exposure to Hg can be influenced by maternal amalgam filling (inorganic Hg) and fish consumption (monomethyl Hg), whereas the risk of exposure to Pb is complex: maternal absorption depends on nutrient interactions (Ca and P); and maternal body Pb accumulation responds to all factors known to interact with bone and calcium metabolism. Maternal exposure to Hg and Pb is more important during fetal development than during breastfeeding. Moreover, these metals (especially Pb) are frequently higher in infant formulas which do not carry the nutritional and psychological advantages and protection of breastfeeding. Infant's reference dose is lower for Hg than for Pb, but risk of Pb contamination for fetuses and infant (breast- or formula-fed) is higher and lasts longer than Hg. Breastfeeding is essential to complete infant development. Interruption or suppression of breast-feeding with cow's milk-based formulas is not an option to environmental pollution."
 

 

Breast-milk mercury concentrations and amalgam surface in mothers from Brasilia, Brazil.

da Costa SL, Malm O, Dorea JG.

Biol Trace Elem Res. 2005 Aug;106(2):145-51.

[abstract only]

 

"Human milk is the best source of nourishment for the newborn because of its incomparable balanced nutrition and psychological benefits to the infant's development. Dental fillings containing metallic Hg are the primary source of inorganic Hg contamination of humans. We studied Hg concentrations in the breast milk of mothers during the first month (7-30 d) postnatal in relation to the number of amalgam surfaces. The concentration of total Hg was determined in 23 samples of human milk collected from lactating mothers with a varied number of amalgam dental restorations. The average number of amalgam surfaces was 6.87 (5.81, SD) with a range of 0 to 20. The mean concentration of total Hg in breast milk was 5.73 ng/g (range: 0-23.07). The Pearson correlation coefficient was significant (r = 0.6087, p = 0.0057) between breast-milk Hg and number of amalgam surfaces. In 56.5% of low-fish-eating mothers, the amount of Hg likely to be ingested by breast-fed infants is above the World Health Organization reference."
 

 

Maternal thiocyanate and thyroid status during breast-feeding.

Dorea JG.

J Am Coll Nutr. 2004 Apr;23(2):97-101. Review.

[abstract only]

 

"Cyanogenic glucosides are naturally present in plant foods especially in staple foods (cassava) consumed by millions of people in tropical countries. Most traditional processing methods are effective in detoxifying such goitrogens to safe levels of consumption. Nevertheless, residual cyanide (CN) is rapidly metabolized to thiocyanate (SCN) by existing metabolic pathways. There are concerns that goitrogens may reach the nursing infants through breast feeding or cow's milk based formulas. SCN adverse effects are commonly observed in relation to cigarette smoking. Breast-feeding is effective in protecting infants from anti-thyroid effects of eventual or habitual maternal exposure to CN exposure in food (cassava) or recreation habits (cigarette smoking). SCN goitrogenic effects occur secondary to iodine deficiency in special circumstances of high consumption of incomplete detoxified cassava and insufficient protein intake. Only during inadequate protein nutrition can SCN aggravate endemic iodine-deficient disorders (IDD)."
 

 

Maternal mercury transfer.

Dorea JG, Barbosa AC.

Environ Res. 2003 Oct;93(2):113-4.

[citation only]

 

 

Iodine nutrition and breast feeding.

Dorea JG.

J Trace Elem Med Biol. 2002;16(4):207-20. Review.

[abstract only]

 

"A survey of the databanks Medline and Web of science identified studies dealing with maternal and infant iodine nutrition during breast feeding. The iodine concentration of human milk varies widely due to maternal iodine intake. Mean breast milk iodine concentrations are reported as ranging from 5.4 to 2170 microg/L (median 62 microg/L) in worldwide studies. In the few studies that compared length of lactation, gestation length, and parity number, these factors did not significantly affect milk-iodine concentrations. In studies of maternal iodine deficiency, untreated goiter had no impact on breast milk iodine when compared with controls. Iodine in human milk responds quickly to dietary iodine intake, either supplemented or consumed in natural foods. Easily absorbable iodine from foods, supplemental sources, iodine-based medication or iodine-based antiseptic solutions used during parturition, is taken up by the maternal thyroid and mammary glands through the Na(+)/I(-) symporter system. This transmembrane carrier protein transports iodine against a high concentration gradient. Hormonal iodine in breast milk occurs mainly as T-4, but depending on maternal iodine intake, high concentrations of the inorganic form (iodide) are found. In less developed countries, where natural-food-iodine intake is low, adequate maternal iodine nutritional status depends exclusively on enforcement of food iodination. In industrialized countries, maternal iodine intake has increased as a function of increasing consumption of dairy products. The human infant is sensitive to maternal iodine nutrition during fetal development and later during breast feeding. Environmental factors, not directly related to maternal iodine intake, such as intake of selenium and organochlorine pollutants, can affect thyroid hormone homeostasis in breast-fed infants. In spite of low iodine concentrations found in milk of mothers consuming low-iodine natural foods, long lasting or even life-lasting benefits to the breast-fed infant are demonstrable."
 

 

Selenium and breast-feeding.

Dorea JG.

Br J Nutr. 2002 Nov;88(5):443-61. Review.

[abstract only]

 

"The objective of the present review is to discuss Se nutrition during breast-feeding, encompassing environmental and maternal constitutional factors affecting breast-milk-Se metabolism and secretion. A literature search of Medline and Webofscience was used to retrieve and select papers dealing with Se and breast milk. Although Se in natural foods occurs only in organic form, breast milk responds to organic and inorganic Se in supplements. Inorganic Se (selenite, selenate), which is largely used in maternal supplements, is not detectable in breast milk. The mammary-gland regulating mechanism controls the synthesis and secretion of seleno-compounds throughout lactation, with a high total Se level in colostrum that decreases as lactation progresses. Se appears in breast milk as a component of specific seleno-proteins and seleno-amino-acids in milk proteins that are well tolerated by breast-fed infants even in high amounts. Se in breast milk occurs as glutathione peroxidase (4-32 % total Se) > selenocystamine > selenocystine > selenomethionine. The wide range of breast-milk Se concentrations depends on Se consumed in natural foods, which reflects the Se content of the soils where they are grown. Se prophylaxis, either through soil Se fertilization or maternal supplements, is effective in raising breast-milk Se concentration. In spite of wide variation, the median Se concentration from studies worldwide are 26, 18, 15, and 17 microg/l in colostrum (0-5 d), transitional milk (6-21 d), mature milk (1-3 months) and late lactation (>5 months) respectively. Se recommendations for infants are presently not achieved in 30 % of the reported breast-milk Se concentrations; nevertheless Se status is greater in breast-fed than in formula-fed infants."
 

 
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