Spontaneous combustion, vampires, and goitrogens

What do the following have in common:

Lima beans

They are all classified as goitrogens, or foods that have been shown to trigger goiter, or thyroid gland enlargement. Most of them do this either by blocking iodine uptake in the thyroid gland or by blocking the enzyme, thyroid peroxidase. This effect can lead to reduction in thyroid hormone output by the thyroid gland, which then triggers increased thyroid stimulating hormone (TSH) by the pituitary; increased TSH acts as a growth factor on the thyroid, thus goiter.

Add to this list of goitrogens the flavonoid, quercertin, found in abundance in red wine, grapes, apples, capers, tomatoes, cherries, raspberries, teas, and onions. Most of us obtain around 30 mg per day from our diet. Quercetin, often touted as a healthy flavonoid alongside resveratrol (e.g., Yang JY et al 2008), has been shown to be associated with reduced risk for heart disease and cancer. Many people even take quercetin as a nutritional supplement.

Quercetin has also been identified as a goitrogen (Giuliani C et al 2008).

What to make of all this?

Most of these observations have been made in in vitro ("test tube") preparations or in mice. Rabbits who consume a cabbage-only diet can develop goiter.

How about humans? The few trials conducted in humans have shown little or no effect. In most instances, the adverse effects of goitrogens have been eliminated with supplemental iodine. In other words, goitrogens seem to exert their ill thyroid effects when iodine deficiency is present. Restore iodine . . . no more goitrogens (with rare exceptions).

Should we as humans adopt a diet that avoids apples, grapes, tomatoes, red wine, tea, onions, soy etc. on the small chance that we will develop goiter?

I believe that we should avoid these common food-sourced goitrogens with as much enthusiasm as we should be worried about spontaneous combustion of humans or the appearance of vampires on our front porches. We are as likely to suffer low thyroid activity from quercetin or other "goitrogens" as we are to experience the "mitochondrial explosions" that are purported to set innocent people afire.

Comments (17) -

  • Lena

    5/27/2009 12:12:26 AM |

    The advice given by thyroid docs, at least the kind that understand more about it than average and are willing to prescribe Armour, etc, is that you should reduce goitrogen intake while you are first starting treatment for hypothyroidism and/or iodine deficiency, then they're OK to have more of in your diet. The goitrogenic effect of most of them is minimised or negated by cooking anyway. Mine did advise that soy could be a bit more problematic and you should avoid consuming any within four hours of taking your thyroid medication, if you swallow the medication instead of taking it sublingually.

  • maxthedog

    5/27/2009 6:19:28 PM |

    Very interesting!  I was hoping you would follow up your iodine/goiter posts with something about goitrogens.  I'd like to read up on the human trials, if there's anything more than abstracts available.  Any urls handy?  Also, just wanted to say I really appreciate your blog, and thank you.

  • flit

    5/28/2009 2:34:37 AM |

    I have Hashimoto's thyroiditis and my endocrinologist (who is fantastic; she titrates my dose to my symptoms, and has me on Armor) has suggested that I want to take the following two precautions around goitrogens:

    a) Don't eat the "biggies" such as soy within four hours of taking my thyroid medication.

    b) Eat them moderately and fairly steadily; a serious pig-out on raw broccoli or edamame after weeks without may cause a swing, but a normal diet that includes them is no big deal.  This means that I actively want to include these things in my diet (which is good, because I both like them and they are good for me.)  If I keep the amount steady then we can just balance my dose against any goitrogenic effect they might have.

  • pooti

    5/28/2009 12:59:23 PM |

    My understanding of the cruciferous vegetable family is that their goitrogenic effect is negated or at least minimized by cooking or fermentation.

  • Anonymous

    5/28/2009 6:22:31 PM |

    Hi Dr Davis,

    FYI - in case you are not aware, the home testing kit shopping area is not working.  At least I've tried ordering with two different computers with out luck.

  • Dr. William Davis

    5/29/2009 1:24:18 AM |


    Thanks for your comments.

    I like option "b", the most practical and logical.

  • Dr. William Davis

    5/29/2009 1:26:01 AM |


    I believe that the lab test area should be working now.

    We are in the process of transferring all files over to a new website and servers. There may therefore be momentary glitches that shouldn't last more than a few minutes while the programmers make the switch.

    On the bright side, the new website will be more user-friendly.

  • Dr. William Davis

    5/29/2009 1:27:39 AM |


    The easiest way is to just go to PubMed.gov and enter the relevant search terms.

    You will find oodles of studies, many in mice or in vitro preparations, a few in humans. You can specify which--mouse vs. human, for instance, in your choice of search terms.

  • kris

    5/29/2009 12:59:49 PM |

    The researchers claim that the findings provide little evidence that "in euthyroid, iodine-replete individuals, soy foods, or isoflavones adversely affect thyroid function."
    The researchers also stated that "there remains a theoretical concern based on in vitro and animal data that in individuals with compromised thyroid function and/or whose iodine intake is marginal soy foods may increase risk of developing clinical hypothyroidism. Therefore, it is important for soy food consumers to make sure their intake of iodine is adequate." They also claim that "some evidence suggests that soy foods, by inhibiting absorption, may increase the dose of thyroid hormone required by hypothyroid patients."

    This study is suggesting that soy is safe -- unless you have a thyroid condition, or iodine deficiency. It also suggests that soy foods can inhibit absorption of thyroid medication.
    The study doesn't address the fact that it's estimated that as much as one-fourth of the U.S. population is now iodine deficient, and that the number is on the rise. At the same time, many millions of Americans also have undiagnosed autoimmune thyroid disease. At minimum, if you accept the premise of this study, that means that more than 75 million Americans with iodine deficiency may be at risk of thyroid problems from soy consumption. If you include the up to 60 million Americans who have a diagnosed or undiagnosed thyroid condition, almost half of all Americans could be at risk of soy-related thyroid problems.

    It's also troubling to note that the author of this study -- and several other recent studies claiming soy is not a danger to the thyroid, is Mark Messina, PhD. Messina, though not a medical doctor, also goes by the name "Dr. Soy." Messina had been in charge of grant funding at the National Institutes of Health (NIH), where he oversaw a $3 million grant for soy studies. Soon after he left NIH, he was hired to serve on the scientific advisory boards of both the United Soybean Board, and international soy agribusiness Archer Daniels Midland. He still serves on both scientific advisory boards as a paid advisor. In addition to his work on these advisory boards, Messina is a consultant to the United Soybean Board and editor of its soy-related newsletter, and serves as a paid speaker and consultant to promote the positive benefits of soy for the United Soybean Board's "Soy Connection.". Messina has also published a number of books promoting soy. The "Political Friendster" website, which tracks corporate influence, has documented the close relationship between Messina and the various corporate players in the soy industry.

    the full 5 page article can be read at.

  • Anonymous

    5/30/2009 1:51:56 AM |

    Help, I am so confused!

    I have a goiter and nodules diagnosed via an ultrasound screen. I have an appt with my MD to take the next step to do lab etc. I am hoping the goiter is caused by iodine deficiency and not Hashimotos. I have been reading about supplementing with iodine but some folks say take lots (12+ mgs) others say taking more will exacerbate a hypothyroid condition. I have been taking kelp capsules 4 daily supplying 1600 mcg. I have been tempted to up the dose but don't want to mess things up. Should I wait until test results come back, then if it is negative for Hashi's go ahead and do mega doses? or should I not be afraid to supplement?

    Thanks for this blog, and thanks for all the intelligent comments through-out. I have learned so much.

    Laura in Arizona

  • Anonymous

    6/2/2009 12:49:52 PM |

    Hi again Dr Davis,

    I was the one that wrote earlier about having troubles ordering testing kits.  The system still is having trouble - at least with my computers, at home and work.  Thought you might want to know.  
    The error occurs after pressing the submit order button.  

    Below is a cut and paste of what the error says.  Hope this helps!    

    Server Error in '/' Application.
    Retrieving the COM class factory for component with CLSID {17B9BE57-09EA-11D5-897B-0010B5759DED} failed due to the following error: 80040154.
    Description: An unhandled exception occurred during the execution of the current web request. Please review the stack trace for more information about the error and where it originated in the code.

    Exception Details: System.Runtime.InteropServices.COMException: Retrieving the COM class factory for component with CLSID {17B9BE57-09EA-11D5-897B-0010B5759DED} failed due to the following error: 80040154.

    Source Error:

    Line 146:
    Line 147:    Public Function ProcessCC(ByVal PaymentObject As PaymentObjCC) As ArrayList
    Line 148:        Dim pfpro As New PFPro
    Line 149:        Dim Response As String
    Line 150:        Dim pCtlx As Integer

    Source File: E:inetpubwwwrootTYPTYP_MainApp_CodePayflowProPFProProcessor.vb    Line: 148

    Stack Trace:

    [COMException (0x80040154): Retrieving the COM class factory for component with CLSID {17B9BE57-09EA-11D5-897B-0010B5759DED} failed due to the following error: 80040154.]
       PayFlowPro.PFPro..ctor() +13
       PFProProcessor.ProcessCC(PaymentObjCC PaymentObject) in E:inetpubwwwrootTYPTYP_MainApp_CodePayflowProPFProProcessor.vb:148
       Checkout.CompleteOrderCC() in E:inetpubwwwrootTYPTYP_MainproductsCheckout.aspx.vb:970
       Checkout.btnSubmitOrder_Click(Object sender, EventArgs e) in E:inetpubwwwrootTYPTYP_MainproductsCheckout.aspx.vb:1113
       System.Web.UI.WebControls.Button.OnClick(EventArgs e) +111
       System.Web.UI.WebControls.Button.RaisePostBackEvent(String eventArgument) +110
       System.Web.UI.WebControls.Button.System.Web.UI.IPostBackEventHandler.RaisePostBackEvent(String eventArgument) +10
       System.Web.UI.Page.RaisePostBackEvent(IPostBackEventHandler sourceControl, String eventArgument) +13
       System.Web.UI.Page.RaisePostBackEvent(NameValueCollection postData) +36
       System.Web.UI.Page.ProcessRequestMain(Boolean includeStagesBeforeAsyncPoint, Boolean includeStagesAfterAsyncPoint) +1565

    Version Information: Microsoft .NET Framework Version:2.0.50727.3082; ASP.NET Version:2.0.50727.3082

  • Anonymous

    1/8/2010 6:28:02 PM |

    What a great resource!

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    11/3/2010 3:41:19 PM |

    How about humans? The few trials conducted in humans have shown little or no effect. In most instances, the adverse effects of goitrogens have been eliminated with supplemental iodine. In other words, goitrogens seem to exert their ill thyroid effects when iodine deficiency is present. Restore iodine . . . no more goitrogens (with rare exceptions).

  • Lena

    1/21/2011 6:06:50 PM |

    ABOUT THE QUESRCETIN has also been identified as a goitrogen (Giuliani C et al 2008).

    WOW, this is the most detailed information I have seen so far  online about the Resveratrol and flavonoids being goitrogenic,

    I have been searching and searching, as I just had read briefly of an experiment with rats that showed Resveratrol (red wine + grape seeds extract) was causing the thyroid gland to enlarge
    I really appreciate you posting this info

    I have hypothyroidism, I take small doses of Armour and it really works great for me, and was taking Resveratrol too, (which by the way, it seemed to help me a lot, especially with giving strength and gloss to my hair)
    So when i heard about this experiment i was shocked. Then I found out that even all kind of fruits are goitrogenic (as you point out) and tea and greens and garlic and onion and potatoes and beans, but above all, fruit and grapes.

    Is so hopeless, I in fact, by fear, suspended the resveratrol, and now, and is funny, as now I am experiencing some minor hair loss, I am sure due to that I stopped taking this amazing supplement which was helping my hair to grow strongly

    So I am so confused, my doctor as most of doctors, do not have a clue, as there is no enough info about all this and also no willingness to look into this research as well

    He told me to stop taking it
    But as you point out, then we should also stop eating then, as it seems that for one reason or another ,, all food is goitrogenic, soy, brassica greens, all greens, and veggies and fruit and also chickens and animals that seems are fed with goitrogenic grass and seeds
    So what choice do we have?
    ALSO I found this experiment on same PubMed which seems contradictory, I am not a doctor but it seems that it helps to add iodide (which is in iodine)  to the thyroid???

    IS there any MD on this site who might throw some light on this???

    or anyone here who has read more on this quercetin or Resveratrol? or knows about where to find more info about real evidence that flavonoids really work that way in humans????
    (by the way thank you for posting the Giuliani experiment, was that on humans or rats?)

    Does anyone knows of a good medical website or any that provides more information about this confusing subject?
    Please, help, let me know,
    Thank you

  • Lena

    1/21/2011 6:09:52 PM |

    about the QUERCETIN

    here is that experiment URL

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