Should people with thyroid problems beware of soy?

This Week in the HSI Forum

An important warning appears in the HSI Forum this week, posted in a thread titled “Soy-onara” – which, not coincidentally, is also the title of Tuesday’s e-Alert about a Japanese study that examined the effects of soy and other isoflavone-rich foods on breast cancer.

An HSI member who goes by the name of Chefgirl explains that at the age of 12 she was diagnosed as hypothyroid – a condition in which the thyroid gland produces inadequate amounts of two key hormones that help regulate metabolism. She points out that soy plays havoc for people with thyroid problems such as hers because the soy isoflavones limit the cells’ ability to receive thyroid hormones.

Chefgirl writes: “In reality, soy protein is one of the worst things that I could consume, especially on a daily basis. I can’t begin to tell you the difference I felt when I stopped eating soy products, just within 2-3 days.”

What infuriates her – and rightfully so – is that she consumed soy products for 10 years, “thinking I was eating healthy and being told that was the case.”

In particular, I was concerned with one detail in Chefgirl’s posting: her comment that the isoflavones in soy are responsible for thyroid dysfunction. If soy isoflavones cause thyroid problems, wouldn’t that also be true of other sources, such as red clover (which we’ve recommended as an alternative to soy)?

A little legwork with our research sources soon turned up a comment on the Memorial Sloan-Kettering Cancer Center web site, warning that due to the estrogenic activity of red clover, it should be used with caution by patients with hormone-sensitive diseases. And that would include thyroid conditions, of course.

If you consume a high quantity of soy foods, or if you use red clover, here are some of the symptoms of hypothyroid disease that you should be aware of: low energy, slowing of the healing process, edema (swelling, usually in the feet or legs), and unusual changes in skin, nails or hair.

This serves as a perfect reminder that herbal supplements are natural medicines that can have powerful effects and should be used with care. So if you’ve been diagnosed with thyroid problems, you should probably avoid soy, red clover, and other foods or botanicals touted as high in isoflavones. And as always, consult your doctor whenever you use any nutritional or herbal remedy to address a medical condition.

Other topics being discussed on the HSI Forum this week include:

  • If you have any doubt that genetic modification of crops is a hot button issue, just visit the thread “GM Foods,” which has more than 80 postings in a very lively debate.
  • A thread titled “McDonald’s to Eliminate Using Beef” is a reaction to Wednesday’s e-Alert, “McMedicine” (see below), but Big Macs may not be as antibiotic-free as we are supposed to believe.
  • An HSI member named Lee offers a warning in “Forteo, Unsafe Drug for Osteoporosis.”