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).