Rutabaga, swede or yellow turnip. Rutabaga's common name in Sweden is "kålrot" (cabbage root). In Norway it is also called "kålrot", but often also "kålrabi" (which in Sweden and Denmark means kohlrabi). Some claim the vegetable is native to Sweden, but others think it was introduced to Sweden, possibly from Finland or Siberia, in the early 17th century,

Excessive consumption of rutabaga (as well as cassava, maize, bamboo shoots, sweet potatoes, and lima beans) can be associated with hypothyroidism.  Some plant isoflavonoids have profound effects on thyroid hormones and on the hypothalamus-pituitary axis. Genistein and daidzein from soy (Glycine max) inhibit thyroperoxidase that catalyzes iodination and thyroid hormone biosynthesis. Other plants with hypothyroid effects include pearl millet (Pennisetum glaucum) and fonio millet (Digitaria exilis); thiocyanate is found in Brassicae plants including cabbage, cauliflower, kale, rutabaga, and kohlrabi, as well as in tropical plants such as cassava, lima beans, linseed, bamboo shoots, and sweet potatoes. These cyanoglucoside-containing foods release cyanide, which is subsequently detoxified into thiocyanate. Thiocyanate inhibits thyroid iodide transport and, at high doses, competes with iodide in the organification process within thyroid tissue. Goiters may develop when there is a dietary imbalance of thiocyanate-containing food in excess of iodine consumption,

Tobacco smoke is also a source of thiocyanate.

Roman GC.  Autism: Transient in utero hypothyroxinemia related to maternal flavonoid ingestion during pregnancy and to other environmental antithyroid agents. J Neurol Sci. 2007 Jul 23; [Epub ahead of print]