The Cruciferous Concern

Post by Paula Jahn, Registered dietitian and Co-owner at Nourish Northwest

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As a dietitian and cooking instructor, I sing the praises of cruciferous vegetables both for their nutritional benefits as well as for their flavor and culinary uses. The family of vegetables that includes broccoli, cauliflower, kale, collard greens, bok choy, cabbage, rutabaga, Brussels sprouts, and kohlrabi has many redeeming (I’ll get to that justification in a minute) qualities such as anti-cancer benefits, a vegetarian source of  calcium, and many vitamins and minerals.
The question of these vegetables being safe, in terms of thyroid function, has come up recently with individual clients and in cooking classes. With the kale craze showing no signs of decline, I feel the need to address this issue and give my perspective.

We are cruciferous. Please cook.
We are cruciferous. Please cook.

The thyroid is a gland responsible for secreting hormones that regulate metabolism, growth, and development. Raw cruciferous vegetables, in large quantities, may contribute to low thyroid function in those with a family history of thyroid dysfunction or for people with iodine deficiency. Cruciferous vegetables, especially in their raw form, can interfere with thyroid hormone synthesis or a compound found in the vegetables may compete for iodine uptake, an essential mineral for thyroid hormone synthesis. The combination of the kale frenzy and the popularity of high powered blenders can make for a potential problem. A fancy blender can make bunches of raw cruciferous vegetables into a convenient, slurpable beverage. If you’re gulping bunches of raw kale every day, you may be putting yourself at risk. However, according to most experts, the risk is small. Look here for a Q and A with endocrinologist and thyroid expert, Dr. Jeffrey Garber. My rule of thumb is to think, “Is this a reasonable amount to consume? Could I physically eat this quantity in one sitting?” If the answer is “No,” perhaps reconsider the composition of your SuperSmoothie.

If you are in a high-risk category for hypothyroidism, read below for some ways to mitigate the potential damage of these nutritious vegetables.

1. Apply heat. Just a quick blanch, roast, sauté, bake, grill, boil (etc.) diminishes the impact on the thyroid to almost nothing. In my opinion, raw cauliflower and broccoli are unappetizing anyway. Plus, they can wreak havoc on the digestive system. Cook ’em. They taste better that way.

2. Eat extra iodine. In some studies, problems with cruciferous vegetables are only seen in the presence of iodine deficiency. We are at low risk of iodine deficiency in the United States since our salt is iodized. However, those who follow a minimally processed vegan diet may consider adding sea vegetables to their diet. Try Vegan “Tuna” Salad or Miso Soup for a natural dose of iodine.

2. Diversify! This is my number one nutritional principle. With variety, you lessen the potential toxic effects of any one substance while adding nutrients from other foodstuffs that your body needs. Cruciferous vegetables are at their peak this time of year, but so are winter squashes, sweet potatoes, beets, parsnips, celery root…Switch it up. Eat it all. Kale is not the enemy.

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