Cruciferous vegetables, namely broccoli, cauliflower, cabbage, brussels sprouts, mustard greens, turnips, and kale are often not prescribed to thyroid patients as they are believed to interfere with thyroid function. However, an Instagram page called The Nutrition Pyramid recently stated that “no one food can cause health issues” which is why, one can have cruciferous vegetables albeit with a few cooking tweaks.
“The thyroid gland is one of the body’s main powerhouses – and produces the T3 and T4 hormones that control metabolism. To make these hormones, your body uses iodine – about 80 per cent of the iodine you consume is used by your thyroid. If your diet is deficient in iodine, or you have an underactive thyroid, known as hypothyroidism, eating raw cruciferous vegetables such as cabbage, cauliflower can further suppress your thyroid hormone function,” it read.
How do cruciferous vegetables impact thyroid function?
“Goitrojens in cruciferous vegetables inhibit the ability to use iodine. In very large quantity, such vegetables can cause goitre or enlarged thyroid. Such vegetables slow down underactive thyroid which potentially causes hypothyroidism,” said Dr Shazia Khan, clinical dietician and certified diabetic educator, Jain Multispeciality Hospital.
As per the page, another good rule of thumb is to not consume more than one small bowl of cooked cruciferous vegetables each day. Agreed Dr Khan and said “moderation is the key”. “People with hypothyroidism should limit the quantity to a bowl, once a week,” she said.
How does cooking help?
The page mentioned that one need not stop eating cruciferous vegetables. “By cooking or steaming them, the goitrogenic properties (that interfere in the production of thyroid hormones by disrupting the use of iodine) are reduced significantly,” it noted.
Anam Golandaz, clinical dietician, Masina Hospital, Mumbai told indianexpress.com that cooking cruciferous vegetables lessens their goitrogenic properties or goitrogenic effect which ensures that they don’t cause any problem when consumed in normal quantities. “It is also important to keep a tab on how well your thyroid treatment is working,” she said.
Also, a study in humans found that the consumption of 150 g/day (5 oz/day) of cooked Brussels sprouts for four weeks had no adverse effects on thyroid function, as per an Oregon State University analysis. Similarly, consumption of high amounts of cruciferous vegetables has been associated with increased thyroid cancer risk only in iodine-deficient areas, it noted.
Cruciferous vegetables are a rich source of sulfur-containing compounds called glucosinolates (β-thioglucoside N-hydroxysulfates) that impart a pungent aroma and spicy (some say bitter) taste, which helps improve overall health and prevent disease, the research highlights.
According to Golandaz, if one’s thyroid level are normal, one may have more room for choices in their diet. “Don’t underestimate the nutritional value of these vegetables as they are rich sources of fibre and all kinds of vitamins, nutrients, and minerals. So always consult a dietician before making any change in your diet,” she said.