iThei mdcdaelcinfd o c elllllrllll o thec dslblohkphc dseelevated) may find that eating a lot of goitrogens may suppress some of
their own internal thyroid hormone production.
Eating too many cruciferous vegetable in the raw state can, in theory,
cause symptoms of hypothyroidism in someone with otherwise well-
controlled symptoms, but most people with Hashimoto’s should not see
this happening.
Eating cruciferous vegetables (unless a person is otherwise sensitive to
them) should not aggravate autoimmune thyroid conditions and may
even be beneficial for most people with Hashimoto’s (glucosinolates
found in raw crucifers have excellent detoxifying properties).
Those who have hypothyroidism due to iodine deficiency or experience
hypothyroidism symptoms after eating too many can still enjoy cruci-
fers as long as they are cooked or fermented.
Cruciferous vegetables are only goitrogenic when raw. Cooking or lightly
steaming deactivates the glucosinolates, as does fermenting the vegetables
(like in sauerkraut), thus diminishing the goitrogenic activity.
On the other hand, canola oil—a goitrogen found in processed foods—
should be avoided by people with Hashimoto’s.
Soy
Soy is one particular goitrogen that is especially detrimental for
Hashimoto’s patients. The isoflavones genistein, daidzein, and gly-
citein in soy reduce thyroid output by blocking activity of the TPO
enzyme.
Soy has been linked with the development of autoimmune thyroid con-
ditions, and children fed soy formula were almost three times more
likely to develop anti-thyroid antibodies as compared with breast-fed
children.
Studies of soy isoflavones in animals suggest possible adverse effects
such as augmentation of reproductive organs, modulation of endo-
crine function, and anti-thyroid effects. Anti-thyroid effects may also
be propagated by the increasing loss of circulating T4 from the blood
via bile.