Preliminary observations on the effect of dietary brussels sprouts on thyroid function.

Brassica vegetables are the major source of glucosinolates in the human diet. Certain glucosinolates are readily converted into goitrogenic species, notably 5-vinyloxazolidine-2-thione and thiocyanate ion. The effect of dietary Brussels sprouts, a particularly rich source of such glucosinolates, on thyroid function has been examined. Inclusion of cooked Brussels sprouts (150 g daily for 4 weeks) into a normal diet of 10 volunteer subjects had no effect on thyroid function as determined by measurement of thyrotrophic hormone, thyroxine and tri-iodothyronine even though the sprouts contained high concentrations (220 mg/100 g) of glucosinolates. In view of the reported antithyroid activity of 5-vinyloxazolidine-2-thione it is suggested that this lack of activity of cooked Brussels sprouts is due to inactivation during cooking of myrosinase, the specific glucosinolate-degrading enzyme.