Brussel sprouts, broccoli, cabbage, turnips, radishes, among others are vegetables that belong to a family of plants called Cruciferae, typically called cruciferous. Cruciferous vegetables have long been presented as a nutritious group of sulfur containing vegetables that may reduce the risk of mortality from cardiovascular disease and be protective against some types of cancer. (1)(2)
The 2015-2020 Dietary Guidelines for Americans recommend for those eating 1400-2200 calories per day they should consume 1-2 cups per week of dark green vegetables. (3) Many of those beautiful dark green vegetables we are supposed to eat belong to a class of sulfur containing vegetables called cruciferous. So, when I read that people with an underactive thyroid also know, as hypothyroidism should avoid cruciferous vegetables I almost passed out. I have hypothyroidism and I am a cruciferous veggie aficionado.
I had to get to the bottom of this advice to see if it was true. Cruciferous vegetables contain bioactive substances that in animal and human tests have shown to reduce production of thyroid hormone. However, a study involving cooked Brussels sprouts showed that participants who ate approximately ½ cup per day for four weeks had no reduction in thyroid hormone production. (4)
A few reasons why cruciferous vegetables pose no risk to a person with hypothyroidism are:
- A person would have to consume large amounts to have any negative affect. (5)
- Cooking reduces the bioactive substances that are implicated in reducing thyroid hormone production.
- As long as a person has adequate iodine stores there has been no evidence that eating cruciferous vegetables has any negative impact on thyroid hormone production. Additionally, the median iodine stores of Americans are adequate and supplementing with increased amounts of iodine can exacerbate the thyroid condition and is not advised. (6)(7)
Cruciferous veggies provide vitamins, minerals, fiber and the phytonutrients necessary to a healthful diet. Go ahead and roast some Brussels sprouts, eat some cauliflower rice, garnish with sauerkraut and dip a floret of broccoli.
- Zhang X, Shu XO, Xiang YB, et al. Cruciferous vegetable consumption is associated with a reduced risk of total and cardiovascular disease mortality. Am J Clin Nutr. 2011;94(1):240-246.
- Egner PA, Chen JG, Zarth AT, et al. Rapid and sustainable detoxication of airborne pollutants by broccoli sprout beverage: results of a randomized clinical trial in China. Cancer Prev Res (Phila). 2014;7(8):813-823.
- US Department of Health and Human Services and US Department of Agriculture. 2015-2020 Dietary Guidelines for Americans. 8th ed.; 2015.
- McMillan M, Spinks EA, Fenwick GR. Preliminary observations on the effect of dietary brussels sprouts on thyroid function. Hum Toxicol. 1986;5(1):15-19.
- Chu, M., & Seltzer, T. F. (2010). Myxedema Coma Induced by Ingestion of Raw Bok Choy. New England Journal of Medicine, 362(20), 1945-1946. doi:10.1056/nejmc0911005
- Mahan, L. K., & Raymond, J. L. (2017). Krauses food & the nutrition care process. St. Louis, MO: Elsevier.
- Kathleen L. Caldwell, Graylin A. Miller, Richard Y. Wang, Ram B. Jain, and Robert L. Jones. Thyroid. November 2008, 18(11): 1207-1214. https://doi.org/10.1089/thy.2008.0161