Does soy affect the absorption of thyroid medication?

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Permalink Reply by Whole_Body_Healer on April 7, 2008 at 1:37pm

What I have read is that soy can suppress thyroid function, which presumably means the production of thyroid hormones. I don't know how that effects things if it's been removed, but there are lots of other reasons to not consume soy (see the previous discussion on Soy for more info).

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Permalink Reply by Sherry on April 7, 2008 at 2:01pm

Hey Lauren,

I had my thyroid removed in December 2006 and have been taking the synthetics ever since with no problems. My doctors (oncologists) did tell me that some soy products inhibit the absorption of the medication....and I was surprised to hear it as well. I've since done some research and have discovered that natural food soy (such as tempe) is not as bad as the soy in milk, or the additives used in alot of foods we csc girls and guys try to avoid anyway. You could switch to either Almond or Rice Milk too.

As WBH stated, they are other reasons to avoid soy including the build up of mucoid plaque in your intestines which inhibits the elimination process. Clint and Bav are my experts of choice here - they are extremely knowledgeable - and we have had similar blogs/posts on this too (check out the poop group for discussions). Hope this helps...let me know what your endo says, I'm definitely interested.

Hope you're doing well. Sherry

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Permalink Reply by David and Katrina Rainoshek on April 7, 2008 at 2:36pm

Soy:

SOY is a low-mineral food that contains phytin, which robs the body of minerals by chelating essential minerals such as iron, zinc, magnesium etc. out of the body before they can be absorbed. Soy is often genetically modified, and it is one of the top 7 allergens. In 2003, a study was done comparing the bodily IGF-1 increase promoted by 40 grams of soy (the amount in one soy candy bar and a soy shake, or 4 soy patties) vs. 40 grams of milk protein. Soy was found to be almost twice as powerful as milk protein in increasing IGF-1 levels (36% for milk, 69% for soy). This new IGF-1 data potentially places soy in the category of a powerful cancer promoter of the breast, prostate, lung, and colon. The implications are first that this establishes soy as a very kaphagenic food, as IGF-1 is the end product of growth hormone stimulation. Although it is controversial, there are many in the medical world that feel that excessive IGF-1 could stimulate the aforementioned cancers if they are already present. This is why Canada does not allow rBGH milk from the U.S. because it is so much higher in IGF-1. In essence, this is still at the level of theoretical speculation but that we feel merits a preventative attention. Our sense is that one should have at best a minimum of soy in the diet if including any cooked food as part of an 80% live, 20% cooked food cuisine.

While in the last 40 years soy has occupied an important place in the transition from an unhealthy meat-based diet to vegetarian and vegan cuisine, it is time for us to upgrade our food choice to one having more benefits, and fewer negative possibilities. In the 1980s, Stuart Berger, MD, labeled soy one of the seven top allergens—one of the "sinister seven." At the time, most experts listed soy around tenth or eleventh. Bad enough, but way behind peanuts, tree nuts, milk, eggs, shellfish, fin fish and wheat. Today soy, which is at least 90% genetically engineered, is widely accepted as one of "the big eight" that cause immediate hypersensitivity reactions. Scientists are not completely certain which components of soy cause allergic reactions. They have found at least 16 allergenic proteins, and some researchers pinpoint as many as 25 to 30.

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Permalink Reply by Whole_Body_Healer on April 7, 2008 at 3:29pm

David, lots of helpful info. IGF-1 is also thought to effect Ovarian Cancer as well, although since it is not one of the "biggees" (in terms of numbers), it is less studied. All of the cancers you mentioned have an estrogenic component as well, which suggests that the interplay of hormonal balance in our systems is VERY important. We consume things, from food (both directly & indirectly) and thru our environment (plastics, pesticides, etc), & really have very little understanding how this effects us.

Do you have any info on the interplay of our various hormonal systems with each other, by chance? Thanks.

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Permalink Reply by David and Katrina Rainoshek on April 7, 2008 at 2:37pm

Soy Affects the Brain via the Thyroid Gland

Tyrosine is crucial to the brain in another way. It’s needed for the body to make active thyroid hormones, which are a major physiological regulator of mammalian brain development. By affecting the rate of cell differentiation and gene expression, thyroid hormones regulate the growth and migration of neurons, including synaptic development and myelin formation in specific brain regions. Low blood levels of tyrosine are associated with an underactive thyroid gland.

It is well known that isoflavones in soy products can depress thyroid function, causing goiter (enlarged thyroid gland) and autoimmune thyroid disease. In the early 1960s, goiter and hypothyroidism were reported in infants fed soybean diets.14 Scientists at the National Center for Toxicological Research showed that the soy isoflavones genistein and daidzein "inhibit thyroid peroxidase-catalyzed reactions essential to thyroid hormone synthesis."15

Japanese researchers studied effects on the thyroid from soybeans administered to healthy subjects. They reported that consumption of as little as 30 grams (two tablespoons) of soybeans per day for only one month resulted in a significant increase in thyroid stimulating hormone (TSH), which is produced by the brain’s pituitary gland when thyroid hormones are too low. Their findings suggested that "excessive soybean ingestion for a certain duration might suppress thyroid function and cause goiters in healthy people, especially elderly subjects."16

Thyroid Hormones and Fetal Brain Development
Thyroid alterations are among the most frequently encountered autoimmune conditions in children. Researchers at Cornell University Medical College showed that the "frequency of feedings with soy-based milk formulas in early life was significantly higher in children with autoimmune thyroid disease."17 In a previous study, they found that twice as many diabetic children had received soy formula in infancy as compared to non-diabetic children.18

Recognizing the risk, Swiss health authorities recommend "very restrictive use" of soy for babies. In England and Australia, public health agencies tell parents to first seek advice from a doctor before giving their infants soy formula. The New Zealand Ministry of Health recommends that "Soy formula should only be used under the direction of a health professional for specific medical indications. . . Clinicians who are treating children with a soy-based infant formula for medical conditions should be aware of the potential interaction between soy infant formula and thyroid function."19

Thyroid hormones exert their influence during discrete windows of time during development of the infant. Inappropriate hormone levels can have a devastating effect on the developing human brain, especially during the first 12 weeks of pregnancy when the fetus depends on the mother’s thyroid hormones for brain development. After that, both maternal and fetal thyroid hormone levels affect the central nervous system.

A 1999 study published in the New England Journal of Medicine showed that pregnant women with underactive thyroids were four times more likely to have children with low IQs if the disorder were left untreated. The study found that 19 percent of the children born to mothers with thyroid deficiency had IQ scores of 85 or lower, compared with only 5 percent of those born to mothers without such problems.20

Thyroid, Brain, and Environmental Toxins
Children exposed prenatally and during infancy to common environmental toxins like dioxin and polychlorinated biphenyls (PCBs) can suffer behavioral, learning, and memory problems because these chemicals may be disrupting the normal action of thyroid hormone.21

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Permalink Reply by David and Katrina Rainoshek on April 7, 2008 at 2:41pm

Soybeans grown in the United States contain residues of the pesticide dieldrin, an organochlorine similar to DDT. Although both chemicals were banned in the 1970s, dieldrin still persists in soils and is absorbed through the roots. Today it is the most toxic residue found on domestic soybeans.22 In Silent Spring, Rachel Carson warned that dieldrin is nearly 50 times as poisonous as DDT. In addition to disrupting hormones, it can have long delayed neurological effects, ranging from loss of memory to mania.23 Chinese aphids were recently discovered in fields scattered across Wisconsin, so increased pesticide applications are likely.

Combinations of insecticides, weed killers, and artificial fertilizers--even at low levels--have measurable detrimental effects on thyroid and other hormones as well as on the brain.24 EPA scientists now want to upgrade the commonly used herbicide, atrazine, to a "likely carcinogen." In animal tests, atrazine attaches to sites on the hypothalamus, a crucial brain region involved with regulating levels of stress and sex hormones.25
Individuals newly diagnosed with Parkinson’s disease were more than twice as likely to have been exposed to insecticides in their home, compared to those without the disease.26 In September 2000, The Lancet reported that farmers and gardeners regularly exposed to pesticides may have more than five times the risk of developing mild cognitive dysfunction.

Soy formulas for infants can contain other neurotoxins: aluminum, cadmium, and fluoride. Studies found that aluminum concentrations in soy-based formulas were a 100-fold greater compared to human breast milk,27 while cadmium content was 8-15 times higher than in milk-based formulas.28 In an Australian study, the fluoride content of soy-based formulas ranged from 1.08 to 2.86 parts per million. The authors concluded that "prolonged consumption (beyond 12 months of age) of infant formula reconstituted with optimally-fluoridated water could result in excessive amounts of fluoride being ingested."29 A study of Connecticut children revealed that mild to moderate fluorosis was strongly associated with soy-based infant formula use.30

In May 2000, Boston Physicians for Social Responsibility released their report, "The Toxic Threats to Child Development." In the section on neurotoxins, they concluded, "Studies in animals and human populations suggest that fluoride exposure, at levels that are experienced by a significant proportion of the population whose drinking water is fluoridated, may have adverse impacts on the developing brain."31

FOOTNOTES
14. Shepard TH, Soybean goiter. New Eng J Med 1960;262:1099-1103.
15. Divi RL, Chang HC, Doerge DR, Anti-thyroid isoflavones from soybean: isolation, characterization, mechanisms of action. Biochem Pharmacol 1997 Nov 15;54(10):1087-96.
16. Ishizuki Y, Hirooka Y, Murata Y, Togashi K, The effects on the thyroid gland of soybeans administered experimentally in healthy subjects. Nippon Naibunpi Gakkai Zasshi 1991 May 20;67(5):622-29.
17. Fort P, Moses N, Fasano M, Goldberg T, Lifshitz F, Breast and soy-formula feedings in early infancy and the prevalence of autoimmune thyroid disease in children. J Am Coll Nutr 1990 Apr;9(2):164-67.
18. Fort P, Lanes R, Dahlem S, Recker B, Weyman-Daum M, Pugliese M, Lifshitz FJ, Breast feeding and insulin-dependent diabetes mellitus in children. Am Coll Nutr 1986;5(5):439-41.
19. Regulatory Guidance in other countries: New Zealand Ministry of Health Position Statement on Soy Formulas (http://www.soyonlineservice.co.nz/regulat.htm)(Adobe Acrobat PDF file: http://www.soyonlineservice.co.nz/files/mohsoy.pdf)
20. Haddow JE, Palomaki GE, Allan WC, Williams JR, Knight GJ, Gagnon J, O’Heir CE, Mitchell ML, Hermos RJ, Waisbren SE, Faix JD, Klein RZ, Maternal thyroid deficiency during pregnancy and subsequent neuropsychological development of the child. N Engl J Med 1999 Aug 19;341(8):549-55.
21. Hauser P, McMillin JM, Bhatara VS, Resistance to thyroid hormone: implications for neurodevelopmental research on the effects of thyroid hormone disruptors. Toxicol Ind Health 1998 Jan-Apr;14(1-2):85-101.
22. Groth E, Benbrook CM, Lutz K, Update: pesticides in children’s foods, an analysis of 1998 USDA PDP data on pesticide residues, Consumers Union of U.S., Inc., May, 2000 (Adobe Acrobat PDF file).
23. Hayes WJ, The toxicity of dieldrin to man. Bull World Health Organ 1959;20:891-92.
24. Porter WP, Jaeger JW, Carlson IH, Endocrine, immune and behavioral effects of aldicarb (carbamate), atrazine (triazine) and nitrate (fertilizer) mixtures at groundwater concentrations. Toxicol Ind Health 1999 Jan-Mar;15(1-2):133-50.
25. Watson, Traci, Common herbicide likely causes cancer. USA Today, June 29, 2000.
26. Nelson L, American Academy of Neurology’s 52nd annual meeting in San Diego, CA, April 29-May 6, 2000.
27. McGraw M, Bishop N, Jameson R, Robinson MJ, O’Hara M, Hewitt CD, Day JP, Aluminium content of milk formulae and intravenous fluids used in infants.Lancet 1986 Jan 18;1(8473):157.
28. Dabeka RW, McKenzie AD, Lead, cadmium, and fluoride levels in market milk and infant formulas in Canada. J Assoc Off Anal Chem 1987;70(4):754-57.
29. Silva M, Reynolds EC, Fluoride content of infant formulae in Australia. Aust Dent J 1996 Feb;41(1):37-42.
30. Pendrys DG, Katz RV, Morse DE, Risk factors for enamel fluorosis in a fluoridated population. Am J Epidemiol 1994 Sep 1;140(5):461-71.
31. Schettler T, Stein J, Reich F, Valenti M, In Harm’s Way: Toxic Threats to Child Development. (http://www.igc.org/psr/ihw.htm) Greater Boston Physicians for Social Responsibility, May 2000.

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Permalink Reply by buddhababy on April 7, 2008 at 4:44pm

I grew up eating soyfoods such as tofu, tempeh and miso. I have no doubt that they played a major role in non specific autoimmune thyroiditis which also played a role in me having had DCIS. After delving into research around 13 years ago regarding soyfoods and thyroid problems I decided to lay off all soyfoods (as well as eliminate grains from my diet) and was abler to get off Armour thyroid. I played the role of guinea pig and would as an experiment eat whole grain+ soy (such as rice) and then get my thyroid levels tested and each time no fail my TSH level would go up. EVERY SINGLE TIME!

WHile I am grateful for the information on soy as published by Sally Fallon and other WAPF related interest groups and feel thatThe Whole Soy Story is a good book and I was once involved with the WAPF, however it's push to lead people towards animal based products does the public a disservice IMHO.

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Permalink Reply by Lauren a.k.a Lau on April 7, 2008 at 5:27pm

Wow..this info is amazing. I too have thyroid cancer and Hashimoto's Thyroiditis and also LOVED my soy milk. I noticed that milk and dairy caused me to break out in horrid acne, so I cut it from my diet and replaced dairy with soy. And I was also on the pill as well for a year. Within a month of taking the pill, my breasts grew from a modest B cup to a D cup! And a month or so later, I was too big for a D! (Now I am not complaining that the girls grew- but I was alarmed at the rate they grew.) My acupuncturist also was worried. Then I found my thyroid tumor 4 months into taking the pill.

Now I know soy mimicks estrogen and probably explains how I became 'Chesty LaRue' in a matter of months... and estrogen is what fuels breast cancer. The pill, plus consuming soy products on a daily basis... I stopped the pill immediately and cut soy out as well. I drink low fat organic milk, but try to find my calcium and protein elsewhere. I also heard that soy blocks thyroid medication as well. Scary stuff..

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Permalink Reply by Caroline on April 8, 2008 at 7:20am

Well, personally I hate tofu so I am okay with the fact that it interferes with thyroid medication! However, after being on this for so long (since 1981), I am concerned that yet another product interferes with thyroid medication. It is quite a list of things... In terms of soy and breast cancer, I was told it is okay to eat soy products but not soy supplements. In other words, tofu is okay.

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Permalink Reply by Daria on April 8, 2008 at 9:21pm

Interesting, I never knew that! Ok, so so far no sugar, no soy, no meat.... Damn it!!! LOL

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Permalink Reply by Lauren a.k.a Lau on April 8, 2008 at 9:34pm

Yeah, I love meat...especially chicken and beef.
My acupuncturist says I need meat- so I only do red meat once a week and I make sure it's organic. Nothing like an organic filet cut steak on the grill! (*drool*)

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Permalink Reply by Laura on April 21, 2008 at 10:45am

I haven't heard that but my naturopathic doctor that I hired in an attempt to shrink my 2 thyroid nodules 2-yrs prior to my Feb '08 thyroidectomy, switched me from my regular soy milk to almond milk & does not include soy in my diet still, now that I'm taking Cytomel. She also does not include tofu in my diet. I will shoot her an email & ask about it. In that same kind of weird vein that you brought up, did you know that people with thyroid issues shouldn't use toothpaste that has fluoride? That of course includes all tap water as well but I'm sure we all know NO TAP WATER anyway! Thanx!

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