Thyroid, Goitrogens, and Gluten Intolerance
I have written quite a bit about the benefits of leafy green vegetables on a gluten-free diet, and am always recommending to clients, family, and friends to drink green smoothies. It is very important to note that there are substances in these nutrient filled powerhouses that aren’t so good for some of us, especially for the very high percentage of gluten intolerant people who have either some type of thyroid disorder or nutrient absorption challenge (1,2). Don’t worry, you aren’t going to read this post and feel like you have doubled the length of your “do not eat list.” Instead, you will learn how to prepare your leafy green veggies for optimal health instead of feeling you need to cut more foods out of your diet. Here is the low down on the good, the bad, and the confusing on veggies and your thyroid:
Thyroid Disorders and Goitrogens
A goitrogen is a food (or chemical) that can inhibit thyroid function. The Brassicas family (aka Cruciferous veggies) are known for their cancer-inhibiting qualities (1), but they are also goitrogenic. Cruciferous vegetables contain a thyroid hormone inhibiting enzyme in their raw state. The most consistent recommendation found in research regarding goitrogenic green veggies is simply to cook them thoroughly before consuming. Thus, the following Brassicas vegetables are not the best choices for green smoothies or raw salads but are fine eaten well-cooked in moderate portions:
Arugula, bok choy, brussel sprouts, broccoli, cabbage, cauliflower, collard greens, daikon, kale, kohlrabi, radish, rutabaga, turnips, and watercress.
There are other ways you can enjoy the health benefits of Cruciferous vegetables without worrying about their goitrogenic qualities. According to Dr. Marcelle Pick, OB/GYN, the key to thyroid health is to get enough iodine in your diet, as well as other micronutrients essential to thyroid function. She suggests pairing goitrogenic foods with the iodine-rich and micronutrient-rich foods to counter the negative effects. For a list of all the micronutrients essential to thyroid function and a list of iodine-rich foods, please see Dr. Pick’s excellent article Eating to Support Your Thyroid.
(1) Digestive Diseases and Sciences, February 2000;45:403-406. Dr. Tarcisio Not of Clinica Pediatrica, I.R.C.C.S., Trieste, Italy
(2) The Celiac/Autoimmune Thyroid Connection. Research links Celiac Sprue Gluten-Intolerance to autoimmune thyroid disease. Mary Shomon, About.com. Updated: October 17, 2008. http://thyroid.about.com/cs/latestresearch/a/celiac.htm#ref
(3) J. Biol. Chem., Vol. 278, Issue 23, 21136-21145, June 6, 2003, Plant-derived 3,3′-Diindolylmethane Is a Strong Androgen Antagonist in Human Prostate Cancer Cells, Hien T. Le, Charlene M. Schaldach, Gary L. Firestone, and Leonard F. Bjeldanes, Department of Nutritional Sciences and Toxicology and Department of Molecular and Cell Biology, The University of California, Berkeley, California 94720-3104 and Lawrence Livermore National Laboratory, Livermore, California 94550