Q. About six months ago, I started eating large amounts of raw cruciferous vegetables, unaware that this affects thyroid levels. Yesterday, I went for an annual physical with blood work, and the doctor said it looks like my thyroid is out of whack. I may be hypothyroid.

If I stop eating broccoli, cabbage and other raw crucifers, will this make the thyroid levels return to normal?

A. Research on this question is surprisingly scarce. Although some data suggest that soy may affect thyroid function, there is almost nothing about vegetables such as broccoli, Brussels sprouts or cabbage. They have traditionally been considered to cause goiter, but it is possible that they have negative effects on thyroid only when consumed raw (Human Toxicology, Jan. 1986) or when thyroid function is already under stress (Journal of Medicinal Food, Winter, 2003).

These vegetables are prized as part of a heart-healthy, anti-cancer diet. We suspect that if your vegetable consumption is responsible for changing your thyroid hormones, it should return to normal within a few months of reducing your crucifer intake. Please let us know the results of your “experiment.”

You can learn more about how to interpret thyroid panel results, as well as approaches to treating hypothyroidism, in our Guide to Thyroid Hormones.

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  1. Lmh

    I used to eat cabbage, but about twenty years ago I started having abdominal cramping after eating it. Finally, it came to the point a few years ago that even a small amount found in my salad could send me into severe cramps, diarrhea and misery for at least two days. My doctors have never heard of a sensitivity to cabbage. Do you have any ideas about this?

  2. jkc

    I had the same problem with walnuts. I’ve been on thyroid medication for over 20 years with no problem. Then everyone, including my eye doctor, began recommending walnuts as a source of omega 3, etc. As I love nuts, I began using chopped walnuts on my breakfast cereal. I started getting symptoms, and my thyroid level suddenly went down. The next refill I got had a warning from the pharmacy to avoid soy, which had been there for ages, but, now, also avoid walnuts.
    I looked at the Mayo Clinic website for thyroid and the very first thing on the list to avoid was walnuts. I suspect that as they’re telling everyone to eat walnuts, they may be finding this out. My doctor says any change in diet can affect thyroid, as well as other medications, especially high fiber, which those vegetables also provide. I guess if you change diet, even for the healthier, you have to recheck thyroid, maybe increase the dose, which I have done.

  3. Sue

    I always steam mine and only have them raw now and again.

  4. Kathy

    I had a similar experience years ago when I was consuming raw kale regularly as a salad veggie. Things did go back to normal when I stopped.

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