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This post was updated on Jan. 29, 2014.

[My Essential Thyroid Cookbook features a chapter called “The Myth of ‘Goitrogens’ ”.]

‘Tis the season! Farmers’ markets are hoppin’ all across the country, and the CSA boxes are being delivered in droves. Some of the healthiest vegetables around are making their appearances in markets now – those dark, leafy greens, kohlrabi, broccoli, and cabbage, to name a few.

Without question, leafy greens and cruciferous vegetables are some of the most health-giving foods on the planet. So it’s a no-brainer that we should load up on as many as we can, right? Even if we have Hashimoto’s? A resounding “yes.”

For those of us with Hashimoto’s and non-autoimmune hypothyroidism, the “goitrogenic” compounds in these foods have made adding these nutritional powerhouses to our diets complicated and confusing, particularly given the onslaught of warnings about goitrogens that you may hear or read from folks who haven’t stayed abreast of the science.

What are goitrogens?
Goitrogens are naturally-occurring compounds found in many whole foods, to varying degrees. Some research – on animals – has suggested that they may suppress thyroid function by interfering with iodine uptake, in essence, slowing the thyroid’s absorption of iodine. This, in turn, could cause a goiter, or so it’s claimed.

A goiter is an enlargement of the thyroid (hence the name). Many of us have been told that goitrogens may also inhibit the production of thyroid hormone. For those of us who have trouble producing thyroid hormone, we certainly don’t want anything hampering thyroid function, true. But goitrogenic foods have been vilified and it’s time to set the record straight.

In describing goitrogenic compounds in scientific detail, The World’s Healthiest Foods writes:

“Over the past 50 years…researchers [of goitrogenic compounds] have determined that there are no such ‘negative’ substances in food, but only health-supportive nutrients that are not a good match for certain individuals because oftheir unique health history and health status. Five decades of research has also determined that certain nutrients – like tyrosine, iodine, and selenium – play a unique role in thyroid health. What has emerged from this scientific work on diet and health is a shift from a focus on ‘negative’ foods that might be ‘bad’ for the thyroid to a new focus on the need to create a right fit between each person’s diet and the nutrients needed by his or her thyroid for optimal function.”

Cruciferous vegetables and soy-based foods generally have the highest levels of so-called “goitrogenic” compounds:

Bok choy
Broccoli
Broccolini
Brussels sprouts
Cabbage
Canola
Cauliflower
Chinese cabbage
Choy sum
Collard greens
Horseradish
Kai-lan (Chinese broccoli)
Kale
Kohlrabi
Mizuna
Mustard greens
Radishes
Rapeseed (yu choy)
Rapini
Rutabagas (swedes)
Tatsoi
Turnips
Tempeh
Tofu
Edamame

The following other foods likely have mild amounts of so-called “goitrogens”:

Peanuts
Strawberries
Flax
Peaches
Millet
Sweet potatoes
Pears
Spinach
Pine nuts
Bamboo shoots

Conflicting information
Because of their potential to affect iodine absorption, those of us with hypothyroidism may be inclined to avoid the foods listed above, but that would be a big mistake. Many leaders in the functional medicine community caution against throwing the baby out with the bathwater. In other words, these foods contain too many beneficial nutrients and are far too beneficial to the immune system (i.e. beneficial to those with Hashimoto’s) to eliminate them from our diets (the primary exception is soy, which we discuss below). The evidence that such goitrogenic compounds pose significant risk to thyroid function is greatly suspect.

Dr. Datis Kharrazian states, “Any practitioner giving people lists of these foods and telling them not to eat them is outdated.”   

Dr. Joel Fuhrman clarified the research in a recent blog post:

“Concerns about potential effects of cruciferous vegetables on thyroid function arose from animal studies, followed by findings suggesting that certain breakdown products of glucosinolates could interfere with thyroid hormone synthesis or compete with iodine for uptake by the thyroid. However, this is only a hypothetical issue. The scientific consensus is that cruciferous vegetables could only be detrimental to thyroid function in cases of iodine deficiency or insufficient iodine intake.”

What’s more, according to Dr. Fuhrman – and this is a biggie – “No human study has demonstrated a deficiency in thyroid function from consuming cruciferous vegetables.” 

Dr. Alan Christianson, a Phoenix, AZ-based naturopath who specializes in thyroid disorders, agrees. He argues that if an individual’s hypothyroidism is NOT caused by iodine deficiency – which is the case for about 95% of hypothyroid sufferers – there’s no need to worry about the potential for slower iodine absorption. 

Chris Kresser, acupuncturist and integrative medicine practitioner, reports that in countries where iodine has been added to table salt, the incidence of autoimmune thyroid disease has increased, “[b]ecause increased iodine intake, especially in supplement form, increases the autoimmune attack on the thyroid.” If this holds true, mild inhibition of iodine absorption may actually prove beneficial for Hashimoto’s patients. 

Furthermore, if there is a potential risk to thyroid function by consuming cruciferous vegetables containing goitrogenic compounds, it may be outweighed by the benefits those same vegetables can provide. For example, many foods containing goitrogens help the body produce glutathione, a powerful antioxidant (“the master antioxidant”) that’s one of the pillars of fighting Hashimoto’s, as it modulates and regulates the immune system, dampens autoimmune flare-ups, and protects and heals thyroid tissue. And it detoxifies the liver to boot. Cruciferous vegetables also help protect against thyroid cancer.

As Dr. Fuhrman says, “Eating cruciferous vegetables is not optional.”

How to protect your thyroid
So, where does all of this information leave us?

Dr. Fuhrman sums it up:

“The fear (circulating the internet by some authors) of eating cruciferous vegetables or that those with hypothyroidism should reduce or avoid the consumption of kale or other cruciferous vegetables is unfounded and does a disservice to the community. Whether you have normal thyroid function or hypothyroidism, there is no benefit for you to avoid or restrict your intake of cruciferous vegetables.”

Many of the foods containing goitrogenic compounds are simply too beneficial to our digestive, skeletal, cardiovascular, and immune systems to eliminate them from our diets. These foods can and should have their places on our plates. But if you’re one of the 5% who has non-autoimmune hypothyroidism (as a result of iodine deficiency, NOT Hashimoto’s), keep a couple of things in mind.

First, cooking inactivates most goitrogenic compounds. In other words, any potential harm to your thyroid exists only when the foods are eaten raw. So roast, steam, sauté, or blanch these foods, and then enjoy to your heart’s desire. 

If you love to add fresh greens to your morning smoothies, try blanching the greens and then freezing them in single-serving portions, like in an ice cube tray. They’ll be as easy to add to the blender as your frozen fruit. 

Also, experiment with cooking foods that are traditionally eaten raw, like strawberries and radishes. We’ve included a few recipes (below) to get your creative juices flowing.

Remember that for soy-based foods, goitrogens are not the only health concern. Soy can have an estrogenic effect in the body, and again, many of us with thyroid issues find that we are prone to estrogen-dominance. So, as we’ve advised before, choose fermented soy foods, and eat them only occasionally.

Second, for those foods that are best eaten raw (or if you have a hankerin’ for crunchy, raw broccoli or homemade coleslaw), as with most things in life, moderation is key. As Dr. Fuhrman describes, “A person would have to consume an insane amount of raw cruciferous vegetables to have a negative effect on thyroid function.”

So, during the spring and summer, when you want to revel in the bounty of arugula salads and big bowls of fresh strawberries, know that a few servings a week of these foods are not likely to do your thyroid any real harm. Enjoy the variety of produce the season has to offer, rotating what you choose so you’re not eating too much of the same thing. (This is good advice for everyone, regardless of whether you have thyroid issues. A critical component of a healthy, holistic diet is moderation and variety, whenever possible. It’s the best way to ensure we’re getting the right amounts of everything our bodies need.)

So as you head off to the market, don’t fear the crucifers. Just use your common sense and your stove. Your thyroid won’t mind, and the rest of your body will thank you.

Savoy Cabbage and Kale Saute

Serves 4

1 tbsp. butter
2 onions, diced
2½ cups water
6 cups washed and coarsely chopped kale, with stems removed
4 cups shredded savoy cabbage, about ¼ in. thick
Salt to taste
Umeboshi vinegar or lemon juice to taste (optional)

In a large skillet, heat butter over medium heat. Add onions and sauté for 10 to 15 minutes, until soft and translucent. Do not burn. While onions are cooking, bring 2 cups of the water to a boil in another skillet that has a tight-fitting lid.  Add kale, cover and cook for 4-5 minutes, until tender. Drain and set aside. (Save liquid for drinking, if desired.) When onions are tender, stir in savoy cabbage and remaining ½ cup water. Cover and cook for 6 to 8 minutes, stirring occasionally, until cabbage is tender but still bright in color. Stir in the cooked kale and heat through. Season to taste with salt and umeboshi or lemon juice, if desired.

From Greens Glorious Greens! by Johnna Albi & Catherine Walthers

Kohlrabi Chowder

6 strips bacon, diced
1 medium onion, chopped
1 clove garlic, minced
4 cups chicken broth
4 cups kohlrabi, peeled and cubed
4 cups potatoes, peeled and cubed
1 cup heavy cream
Salt and white pepper to taste
2 tbsp parsley, chopped

Fry bacon in heavy soup pot over medium heat until done; remove and drain on paper towels. Drain off all but about 1 tbsp. of bacon fat. Add chopped onion and sauté until glassy – do not brown. Add garlic and sauté one minute longer. Add chicken broth, kohlrabi, and potatoes. Bring to a boil and simmer, partially covered, over medium heat until potatoes and kohlrabi are soft and soup becomes thick. Stir frequently so soup does not scorch. Remove from heat. Mash or puree if a less chunky soup is desired. Add cream, salt, white pepper, and parsley. Add bacon. Reheat (do not boil) and serve. Makes 8 servings.

From Hilltop Produce Farm, in the 2005 St. Paul Farmers’ Market cookbook

Braised Red Radishes

20 plump radishes, red or multicolored
1 to 2 tbsp. butter
1 shallot, diced
1 tsp. chopped thyme or several pinches dried
Salt and freshly milled pepper

Trim the leaves from the radishes, leaving a bit of the green stems, and scrub them. If the leaves are tender and in good condition, wash them and set aside. Leave smaller radishes whole and halve or quarter larger ones.

Melt 2 to 3 tsp. butter in a small sauté pan. Add the shallot and thyme and cook for 1 minute over medium heat. Add the radishes, a little salt and pepper, and water just to cover. Simmer until the radishes are tender, 3 to 5 minutes. Add the leaves if using and cook until they’re wilted and tender, 1 minute more. Remove the radishes to a serving dish. Boil the liquid, adding a teaspoon or two more butter if you like, and until only about ¼ cup remains. Pour it over the radishes and serve.

From Vegetarian Cooking for Everyone, by Deborah Madison

Roasted Strawberries

8 ounces small to medium strawberries, hulled
2 tbsp. maple syrup
1 tbsp. extra-virgin olive oil
½ tsp. fine-grain sea salt
1 tbsp. port wine
A few drops balsamic vinegar

Preheat the oven to 350 degrees, with a rack in the middle of the oven. It’s important to use a rimmed baking sheet or large baking dish for this recipe – you don’t want the juices running off the sheet onto the floor of your oven. If you’re using a basking sheet, line it with parchment paper.

Cut each strawberry in half. If your strawberries are on the large side, cut them into quarter or sixths. Add the berries to a mixing bowl. In a separate small bowl, whisk together the maple syrup, olive oil, and salt. Pour this over the strawberries and very gently toss to coat the berries. Arrange the strawberries in a single layer on the prepared baking sheet.

Roast for about 40 minutes, just long enough for the berry juices to thicken, but not long enough for the juices to burn. Watch the edges of the pan in particular.

While still warm, scrape the berries and juices from the pan into a small bowl. Stir in the port and balsamic vinegar. Use immediately or let cool and store in the refrigerator for up to a week.

Makes about ½ cup.

From Super Natural Every Day by Heidi Swanson