Chris Kresser: I believe we’re going to talk about this soon in the exposome unit, but when it comes to limiting goitrogens, there are a number of different factors to consider. One is the overall iodine status of the patient because the primary effect of goitrogens is to inhibit iodine uptake in the thyroid gland. If iodine intake is really low because the patient has Hashimoto’s and they’ve been told to avoid it, for example, then having a green smoothie with raw kale in it, which is goitrogenic, every morning is probably not a good idea. However, if the patient does have an adequate amount of iodine in their diet from food—maybe they consume sea vegetables or fish like cod or dairy products—then even with a relatively substantial intake of goitrogens, it probably won’t impact their absorption of iodine.
The second factor is whether the foods are cooked or not. Raw goitrogenic foods are higher in goitrogens because the cooking deactivates some of the goitrogens, and different cooking methods have different effects. Steaming deactivates about 30 percent of the goitrogens, and if you boil them and discard the water, which isn’t great from a nutrient density perspective for other reasons, that eliminates 90 percent of the goitrogens in food. Then there’s a range of other cooking methods in between.
We’ll be talking about this more later in the blood chem unit, but most patients I’ve seen with Hashimoto’s don’t respond negatively to iodine, contrary to conventional wisdom, if their selenium levels are adequate. So I still like to get people consuming adequate amounts of iodine because it’s an important nutrient for other reasons, including cancer prevention. I would say for a general Hashimoto’s patient, take adequate iodine if they tolerate it. Number two would be to not eat raw goitrogens every day. An occasional green smoothie with raw kale is fine, maybe two or three times a week, but not every day. Don’t eat raw broccoli every day. Then for the goitrogens that are consumed, cook them. Steam the broccoli well. Yuca/cassava is high in goitrogens, but of course, you have to cook it well in order to eat it. It’s not really edible raw. If you follow those guidelines, the patient will usually be fine. It’s actually important not to completely eliminate goitrogenic foods because many goitrogenic foods are among the most nutrient dense foods in terms of phytonutrients. I hope that helps answer the question.