Kale Smoothie Lovers: your smoothie may be harming you

Do you frequently make smoothies or juice with raw vegetables? If you have hypothyroidism this could be a concern.

Very high intakes of some raw vegetables can interfere with your thyroid function. Raw kale, cabbage, Brussels sprouts, cauliflower, spinach, broccoli, collard greens, kohlrabi, rutabaga, turnips, bok choy and Chinese cabbage, arugula, mustard greens, horseradish, radish, wasabi and watercress contain glucosinolates and naturally release a compound called goitrin when they are  broken down. Goitrin can interfere with thyroid hormone synthesis and contribute to an enlarged thyroid (called goiter). Heating these vegetables negates much or all of this potential goitrogenic effect.

And it’s not just the veggies that can increase the risk of thyroid problems. It’s a combination of factors including potential iodine deficiency. (One of the most common causes of goiters is iodine deficiency.) So make sure you are getting adequate iodine either by purchasing and using iodized salt instead of non-iodized.

In addition to the above mentioned vegetables, if you have thyroid disease its best to limit intake of, peanuts, linseed, pine nuts, and millet.  Some research indicates that soy should also be avoided if you have hypothyroidism. Recent studies suggest that it is safe and definitive conclusions have not been reached.

What to do?
Cook the vegetables I have mentioned and vary the vegetables you do eat. There are many other nutritious vegetables that aren’t goitrogenic such as carrots, bell peppers, romaine lettuce, asparagus, zucchini, beets, for example.

Fenwick GR, Heaney RK, Mullin WJ. Glucosinolates and their breakdown products in food and food plants. Crit Rev Food Sci Nutr. 1983;18(2):123-201.  (PubMed)

Cléro É, Doyon F, Chungue V, Rachédi F, Boissin JL, Sebbag J, Shan L, Rubino C, de Vathaire F.Dietary patterns, goitrogenic food, and thyroid cancer: a case-control study in French Polynesia.Nutr Cancer. 2012;64(7):929-36. doi: 10.1080/01635581.2012.713538.
Alissa EM, AlShali K, Ferns GA.Iodine deficiency among hypothyroid patients living in Jeddah. Biol Trace Elem Res. 2009 Sep;130(3):193-203. doi: 10.1007/s12011-009-8329-6. Epub 2009 Feb 5.

Milerová J, Cerovská J, Zamrazil V, Bílek R, Lapcík O, Hampl R.Actual levels of soy phytoestrogens in children correlate with thyroid laboratory parameters. Clin Chem Lab Med. 2006;44(2):171-4.

Marini H, Polito F, Adamo EB, Bitto A, Squadrito F, Benvenga S.Update on genistein and thyroid: an overall message of safety. Front Endocrinol (Lausanne). 2012 Jul 31;3:94. doi: 10.3389/fendo.2012.00094. eCollection 2012.


Linus Pauling Institute

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