Breast milk cyanide

Cyanide is metabolized by rhodanese in the liver to thiocyanate (Hall and Rumack, 1986). Thiocyanate is excreted mainly in the urine. Without administration of an antidote, the half-fife for tfie metabolism of cyanide to thiocyanate is 20 min to 1 h (Feldstein and Klendshoj, 1954). Cyanide can be excreted in breast milk (Soto-Blancoand Gomiak, 2003). 

Large amounts of thioq anate are generated in people with a high intake of cyanide from tobacco smoking, from cyanide in food, or from industrial pollution of the environment with cyanide. Thiocyanate may also be directly consumed with certain foods. Thiocyanate is a competitive inhibitor of the sodium iodide symporter (NIS) at thiocyanate levels normally found in blood. Thereby, it worsens iodine deficiency by inhibition of thyroidal iodide accumulation and by inhibition of iodide transport into breast milk for infant nutrition. Cessation of smoking, reduction of industrial pollution and improved diet will reduce the role of thiocyanate in thyroid disease. In individuals exposed to high levels of thiocyanate, adverse effects may be prevented by an increase in iodine intake. 

No studies of humans have demonstrated inhibition of iodide transport into breast milk of mothers from thiocyanate in diet. In many countries the most important determinant of thiocyanate levels in blood is tobacco smoking, as discussed above, and smoking is associated with similar increases in thiocyanate in blood as may be found from diets with high cyanide content. We therefore investigated the effect of maternal smoking on iodine transfer to the breast-fed neonate. 

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