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Soy and Your Thyroid

If you have any sort of thyroid disorder, you should pay attention to how much soy you are getting in your diet.  Research shows that people are consuming more soy than ever in the U.S. It’s cheap and is often considered healthier than meat, although that is not the case for people with thyroid problems!

soy, tofu,Most people are aware of the obvious sources of soy, such as tofu, edamame, soy milk and veggie burgers. Less apparent are the protein bars, high-protein cereals, protein powders and meat “extenders” or “analogs” used to make fake everything from chicken nuggets to cheese and bacon bits. Vegans, in particular, may be getting more soy than they suspect.  Soy can be labeled in processed foods as textured vegetable protein (TVP), hydrolyzed plant protein (HPP) or soy protein isolate.

Although soy does have some health benefits, it has a big negative when it comes to your thyroid. Two components of soy, both isoflavones, genistein and equol, a metabolite of daidzen, inhibit an enzyme, thyroid peroxidase, used in the thyroid gland to make both T4 and T3. Diets high in soy can produce goiter (thyroid enlargement) and autoimmune thyroiditis such as Hashimoto’s.  Being low in iodine, a nutrient essential for proper thyroid function, multiplies soy’s negative effects on the thyroid.  Soy can also interfere with you body’s ability to use thyroid replacement hormones.

Research suggests that the thyroid-toxic effects of soy are most often seen at levels above 30 mg of soy isoflavones per day. There are estimates suggesting that Asians consume some 10 to 30 milligrams of isoflavones from soy a day at most — and it’s soy in traditional food form that is not processed or genetically modified. In the U.S., however, some people are getting as much as 80 to 100 milligrams of soy isoflavones a day, by consuming soy milk, soy nuts, soy protein shakes, soy candy bars, soy cereal, and foods enriched with soy, as well as soy supplements.

I’d suggest you avoid soy if you have had problems with your thyroid. If you must have some, limit to two to three servings a week. Do not eat soy foods within three to four hours of taking your thyroid hormone replacement medication, to avoid any interference with your thyroid medication. Do not use soy or isoflavone supplements, which are marketed over-the-counter for hot flashes and other symptoms of menopause.

REFERENCES

de Souza Dos Santos MC, Gonçalves CF, Vaisman M, et. al. Impact of flavonoids on thyroid function. Food Chem Toxicol. 2011 Oct;49(10):2495-502. doi: 10.1016/j.fct.2011.06.074. Epub 2011 Jul 2.

Divi RL, Chang HC, Doerge DR. “Anti-thyroid isoflavones from soybean: isolation, characterization, and mechanisms of action.” Biochem Pharmacol. 1997 Nov 15;54(10):1087-96.

Doerge DR, Sheehan DM. “Goitrogenic and estrogenic activity of soy isoflavones.” Environ Health Perspect. 2002 Jun;110 Suppl 3:349-53. 

 

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8 Comments

  1. Rose August 25, 2013 at 4:20 pm - Reply

    I have hypothyroidism. I take thyroid medication. Why hasn’t my doctor told me about this. I was trying to be healthier and eat more soy. I am guessing that it is why I have not been feeling good for the last 4 year.

  2. Mike August 26, 2013 at 1:46 am - Reply

    @ Rose, because this article is pretty incorrect.
    The whole soy-is-unhealthy-for-the-thyroid (and for many other things) is a pretty huge myth. (Possibly introduced in this world by anti-soy groups like the meat industry).

    Want some soy-thyroid research? Here:
    http://www.ncbi.nlm.nih.gov/pubmed/17316115?ordinalpos=14&itool=EntrezSystem2.PEntrez.Pubmed.Pubmed_ResultsPanel.Pubmed_DefaultReportP%E2%80%8Banel.Pubmed_RVDocSum
    Conclusion: no effect/link.

    By the way, you may also wanna read these great posts (MUST READS actually!):
    http://medcapsules.com/forum/showthread.php?tid=2772
    http://medcapsules.com/forum/showthread.php?tid=2777
    http://medcapsules.com/forum/showthread.php?tid=2784 (thyroid discussion)

  3. Dr. Denis Wilson August 26, 2013 at 5:28 am - Reply

    I do agree that research can be greatly influenced by who’s paying for it. May be best to weigh the evidence and see what works best for the individual.

  4. Linda August 27, 2013 at 6:03 am - Reply

    I do not agree that this is a myth – If you are trying to dispute the article about how soy can negatively affect Thyroid, you have failed with the study you list here. You only have to read a few WORDS of it to see that this study was done using young males. A study using persons with Hypothyroidism might be more telling,

  5. Dawn September 2, 2013 at 7:13 am - Reply

    SOY is the #1 most genetically modified food on the planet and I would not touch it ! Made by Monsanto – it is in everything from tofu to salad dressings.
    It is sold to us as a “healthy” food – but that couldn’t be farther from the truth. I have no doubt it would impair Thyroid function.

  6. Marilyn September 11, 2013 at 6:17 am - Reply

    I have taken this Wilson low temperature program for two months. My pulse skyrocketed and I had severe heart palpitations. None of my symptoms are gone, including weight gain. Why?

    • Dr. Denis Wilson September 11, 2013 at 8:18 am - Reply

      Hi Marilyn, It’s true that some people don’t tolerate T3 therapy well. The people that have a history of palpitations are the ones that are more likely to experience palpitations on T3. There are many possible reasons your pulse could go up and many ways to avoid it as well. I’d be happy to discuss your case with your doctor at 800 420 5801. Cheers.

  7. Marilyn September 11, 2013 at 6:18 am - Reply

    Oh, and my blood work is in the normal range. I am not producing antibodies against it either.

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