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The "Willner Window" Radio Show. Your source of nutritional supplement information and interviews, weekly, for 18 years. Listen to archived mp3 audio files.

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Soy and Thyroid Problems: A Misunderstanding

Soy Lecithin or Soy Isoflavones? --Undue Alarm!

The following is an excerpt from The Willner Window radio program, which can be heard every Sunday afternoon, from 2 to 4 pm, on WOR Radio (710 AM) or over the internet at
Arnie: Good afternoon everyone, this is .... Welcome to The Willner Window. For those of you who might be first-time listeners, the focus of this show is nutritional supplements–vitamins, herbs, homeopathic remedies–and their proper usage. With me this afternoon is . .
Don, did you want to start things off today?  
Don:  Yes, Arnie, thanks.
I had a call from a customer last week who heard something on the morning news that made him worry about a supplement his wife was taking. I’ll give you the details in a moment, but the reason I want to talk about it is that he made a common mistake. He heard the name of a supplement, or nutrient, and because he didn’t really know exactly what he was taking–or in this case, what his wife was taking–he became alarmed.
He didn’t have to be.  
Sam:  Apparently, somebody on one of the morning talk shows cautioned that there might be some interaction between soy and thyroid function.
Now we didn’t hear it, but this is nothing new. It has been known for some time that soy isoflavones have been reported to slightly reduce thyroid function in some people. If you look on our web site,, you will find information on this. In Healthnotes, they provide several references, and the results are not conclusive–some show a slight decrease in thyroid function, some show a slight increase, and some show no change.
Bottom line, if you are taking thyroid medication, you should be cautious about suddenly switching to a high soy intake without notifying your physician.  
Don:  But here is the thing. His wife was taking soy lecithin granules. He heard the word soy, and thought that it was related to her supplement. But it’s not. Soy lecithin granules is derived from soy, but does not contain soy. He had no reason to be concerned. Lecithin, actually, is derived from soybean oil. And the lecithin granules have been concentrated to the point that they don’t even contain hardly any soy oil–it is 95% phospholipids, which are the active constituents of lecithin–things like phosphatidyl choline. They achieve this by removing most of the oil.  
Sam:  Liquid lecithin, by the way, which you can buy in bottles or soft gel capsules, contains about 62% phospholipids. The rest is soy oil.  
Don:  So he made a common mistake, and I

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