What should you eat when you are diagnosed with a condition such as hypothyroidism (underactive thyroid)? Doctors rarely offer advice on this question, partly because they often have little background in nutrition themselves. Sometimes the research is very confusing, which also makes it difficult to offer sound advice.
That leaves the door wide open for exaggerated claims of either benefit or harm, occasionally from the same food. This reader was initially attracted to claims that soy is a superfood, then frightened by the possibility that it might throw her thyroid gland further out of balance. Is either claim true?
Is Soy Milk a Wonder Food?
Q. I read that soy would prevent heart disease and osteoporosis, so I switched from cow’s milk to soy milk. I put it on my cereal and in my coffee every morning and drink a glass at lunchtime as well. I also started using soy sausages and burgers instead of meat.
Then I heard that soy is bad for the thyroid gland. I am hypothyroid. Can you tell me anything more about this connection? Should I give up my soy milk?
What Are the Hazards of Soy Milk or Soy Burgers?
A. The answer to this question is surprisingly complicated. Rodent research suggests that compounds in soy may indeed disrupt thyroid function (Experimental Biology and Medicine, June, 2013; Toxicology and Applied Pharmacology, Jul. 15, 2014).
But research in monkeys shows soy does not seem to interfere with thyroid gland activity (Menopause, Oct., 2014). Since people are presumably more similar to monkeys than to rats and mice, we are left with big questions.
In humans, experiments have been inconsistent (Alternative Therapies in Health and Medicine, Feb., 2014). There are cases of newborn babies whose thyroid conditions worsened when they were fed soy formula (Pediatrics, Sept., 2012). Whether adults are equally susceptible is unknown.
Our Guide to Thyroid Hormones goes into much more detail on diet, diagnosis and treatment of hypothyroidism. This 25-page booklet is available only online ($3.99).
Moderating soy consumption might be prudent. Most experts we have asked, such as Mary Shomon [http://thyroid.about.com] and Ridha Arem, MD, author of The Thyroid Solution Diet, have responded that it is reasonably safe to consume soy products a few times a week, but relying on soy as heavily as you are might put too much strain on the system.