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Tea Thyroid Danger

January 5, 2011 Written by JP       [Font too small?]

Even the healthiest foods and remedies aren’t recommended for certain people. A bowl of freshly picked, organic green leafy vegetables is a wonderful addition to most diets. But it can be a veritable poison if you happen to be allergic to the greens in question. Likewise, exceedingly benign treatments such as massage therapy need to be applied in an individualized manner. Does it make any sense to give a deep tissue massage to someone with a bleeding disorder? The fact of the matter is that all natural remedies ought to be viewed subjectively. Adverse reactions are not the exclusive domain of conventional medicine. (1,2,3)

Black, green and white teas are among the top antioxidant sources in modern and traditional diets. Phytochemicals found in the leaves of Camellia sinensis yield wide ranging health benefits that impact conditions as varied as Alzheimer’s Disease and numerous forms of cancer. However, the irony is that these very same free radical fighters that protect the body can also negatively impact thyroid function. (4,5,6)

Some natural health experts claim that tea’s naturally occurring fluoride content can harm the thyroid. It’s true that some sources of tea do contain fluoride. What’s more, excess intake of fluoride from any source can lead to thyroid dysfunction. This concern is relevant enough for me to recommend asking tea manufacturers whether they test for aluminum, fluoride and other potentially toxic minerals in their products prior to buying them. Having said that, it doesn’t appear that these undesirable elements are predominantly responsible for the anti-thryoid activity in tea. (7,8,9)

The best information we currently have to work with stems from several animal studies on the topic. The latest investigation, published in the August 2010 issue of the journal Human & Experimental Toxicology, describes how green tea has greater anti-thryoidal potential than black tea because of its higher content of polyphenolic flavonoids. This finding is corroborated in other recent examinations which mostly point to select antioxidants known as catechins as the culprit. In animal models higher levels of green tea intake generally bring about dysfunction in the thyroid gland via decreased levels of serum thyroid hormones (T3 and T4), reduced activity of thyroid peroxidase and even thyroid lesions. (10,11,12,13)

Percentage of Symptoms and Signs in Clinical Hypothyroidism

Symptoms (%) Signs (%)
Fatigue 88 Dry coarse skin 90
Cold Intolerance 84 Voice Hoarseness 87
Dry skin 77 Facial Periorbital Oedema 76
Voice Hoarseness 74 Slowed Movements 73
Decreased Hearing 40 Mental Impairment 54
Sleepiness 68 Bradycardia < 60/min 10
Impaired Memory 66 Bradycardia > 60/min 90
Paresthesia 56 Weight Gain 72
Constipation 52 Hair Loss 41

Source: Hippokratia. 2010 Apr–Jun; 14(2): 82–87. (link)

Before jumping to any conclusions, I think it’s important to take a few factors into account. Firstly, the studies available have all been conducted in animal subjects. The results demonstrated in such trials often do not translate to human populations. Also, several observational studies have examined a proposed link between tea consumption and thyroid cancer. If anything, these epidemiological investigations have concluded that tea appears to afford a protective effect. This would argue against the widespread anti-thyroidal activity of tea in a real world setting. (14,15,16)

Related trials in humans have examined the impact of other goitrogenic foods. Most have not raised significant cause for concern. For instance, a recent intervention conducted at the University of South Carolina found that daily consumption of soy protein (67.5 grams/day) failed to “affect thyroid end points” in a group of 25 postmenopausal women. Ensuring adequate dietary iodine also appears to be an important part of the equation. Iodine-replete diets may afford protection against the thyroid suppressive activity of many common foods. But there’s really no sense in playing guessing games with such an important matter. If you consume large quantities of tea or other foods that may affect the thyroid (cruciferous vegetables, peanuts, soy, etc.) make sure to have your thyroid function tested – especially if you exhibit any of the symptoms associated with hypothryoidism. This will allow you and your health care team to make any necessary adjustments to your diet. (17,18,19,20,21)

Be well!

JP

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5 Comments & Updates to “Tea Thyroid Danger”

  1. ewelina Says:

    Your blog is so informative – I agree, even the best thigs for one person migt not be so good for others. It happened to me that I had heard about Endormologie as a very good way of slimming massage – and even though I had issues with my vericose and spider veins I signed up for it – I am sorry to say that the massage maybe helped me loose couple inches, but it increased vein aprearance on my legs, which at this point is irriversible. I think if I had known that I would defintely skipped it. Thank you for your post – I am tea lover but also have thyroid problem. Your post made me search deeper into the issue.

  2. JP Says:

    Thank you for your kind words and for sharing your valuable experience. I appreciate it!

    Be well!

    JP

  3. Liverock Says:

    I have taken a supplement of 400mg of green tea for years and regularly drink about 3 pints of black tea a day(I’m English!).

    A recent thyroid test showed perfect results. I think the fact that tea can prevent excessive iron absorption and is choc a block with polyphenols helps to counteract a lot of the negative aspects of any thyroid problems it may cause.

    Of course it could be I am setting myself up for Alzheimer’s with all that fluoride and aluminium in the tea. C’est la vie!

  4. JP Says:

    Liverock,

    I’m genuinely happy to hear it. Not only because I wish good things for you. But also because I hope that this proposed tea-thyroid connection doesn’t apply to any/most people.

    As for the Alzheimer’s concern, there may still be hope for you:

    http://www.spandidos-publications.com/ijmm/26/1/45

    Be well!

    JP

  5. JP Says:

    Update: Zinc supports healthy thyroid function and health …

    http://www.tandfonline.com/doi/full/10.1080/07315724.2014.926161#abstract

    J Am Coll Nutr. 2015 Mar 11:1-9.

    Effects of Zinc and Selenium Supplementation on Thyroid Function in Overweight and Obese Hypothyroid Female Patients: A Randomized Double-Blind Controlled Trial.

    OBJECTIVE: Zinc (Zn) and selenium (Se) are essential trace elements involved in thyroid hormone metabolism. This study was conducted to investigate the effects of Zn and Se supplementation on thyroid function of overweight or obese female hypothyroid patients in a double-blind, randomized controlled trial.

    METHODS: Sixty-eight female hypothyroid patients were randomly allocated to one of the 4 supplementation groups receiving Zn + Se (ZS; 30 mg Zn as zinc-gluconate and 200 μg Se as high-selenium yeast), Zn + placebo (ZP), Se + placebo (SP), or placebo + placebo (PP) for 12 weeks. Serum Zn, Se, free and total triiodothyronine (FT3 and FT4), free and total thyroxine (FT4 and TT4), thyroid-stimulating hormone (TSH), and anthropometric parameters were measured. Dietary intake was recorded using 24-hour food recall. Physical activity questionnaire was completed.

    RESULTS: No significant alterations were found in serum Zn or Se concentrations. Mean serum FT3 increased significantly in the ZS and ZP groups (p < 0.05) but this effect was significant in the ZP group compared to those in SP or PP groups (p < 0.05). Mean serum FT4 increased and TSH decreased significantly (p < 0.05) in the ZS group. TT3 and TT4 decreased significantly in the SP group (p < 0.05). Mean FT3:FT4 ratio was augmented significantly in the ZP group (p < 0.05). No significant treatment effects were found for TT3, FT4, TT4, or TSH between groups.

    CONCLUSION: This study showed some evidence of an effect of Zn alone or in combination with Se on thyroid function of overweight or obese female hypothyroid patients.

    Be well!

    JP

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