Can cruciferous vegetables, like broccoli, cauliflower, kale and cabbage, damage your thyroid?
Many people regard them as really healthy foods in terms of the many plant nutrients that they contain.
However, some health advocates will warn you against the eating of cruciferous vegetables if you have any thyroid issues.
So what exactly is the truth with regards to the relationship between cruciferous vegetable and thyroid conditions?
What are cruciferous vegetables?
Cruciferous vegetables contain substances known as glucosinolates which actually help protect against certain forms of cancer, including breast, prostate, bladder and lung cancers. (1)
In addition, these vegetables are a great source of vitamins, minerals and phytonutrients, which support bodily health.
At the same time, these vegetables also contain goitrogens. These can actually prevent the body from absorbing iodine which is needed for healthy thyroid functioning.
Generally speaking, if you have thyroid issues, such as hypo or hyper thyroidism, you will hear that you should not consume these vegetables.
Unethical studies were done using animals and feeding them with large amounts of cruciferous vegetables and their thyroid function slowed down. (2)
But then again, can these studies be applied to humans beings as we do not live in laboratories? We are, of course, not biologically exactly the same as other animals.
Another study had people eating 150 grams of cooked Brussels sprouts every day for a month with no sign of any negative health effects on their thyroid. (3)
Studies with humans have revealed no signs of any inability by the human body to absorb iodine when these veggies are consumed, unless they are consumed in huge amounts.
There was one reported case of an 88-year old woman who was eating over a 1-1 ½ kilos of raw bok choy every day for months and has developed hypothyroidism. (4)
But other than that woman, how many people can eat this amount of raw bok choy day in and day out for months? We certainly couldn’t and we don’t know many people who could.
In short, studies have indicated that cruciferous vegetables and thyroid conditions are not related in any significant way.
So the much trumpeted advice about needing to avoid consuming cruciferous veggies for those who are suffering with thyroid issues does not hold stand up to scrutiny.
So if you do enjoy eating your kale, cauliflower, Brussel sprouts, broccoli and other cabbages, the evidence shows that there is no need for you to worry about experiencing unwanted side effects, even if you do have a thyroid issue.
And with regards to iodine – if you are not getting adequate amounts of this vital nutrient from your diet (and many people don’t), then you should consider supplementing your diet with this nutrient.
What are your thoughts and experiences regarding cruciferous veggies and your thyroid health? Please share below!
(2) Higdon J, Drake VJ: Cruciferous Vegetables. In An Evidence-based Approach to Phytochemicals and Other Dietary Factors 2nd edition: Thieme; 2013
(3) McMillan M, Spinks EA, Fenwick GR: Preliminary observations on the effect of dietary brussels sprouts on thyroid function. Hum Toxicol 1986;5:15-19.
(4) Liu X, Lv K: Cruciferous vegetables intake is inversely associated with risk of breast cancer: A meta-analysis. Breast2012.
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