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Thyroid test

What you eat matters. Certain foods improve or disrupt your health. For example, iodine is an essential component of thyroxine, necessary for healthy thyroid hormone function. But thiocyanate in many common foods can override the benefits of dietary iodine.

Thiocyanate is a potent molecule that inhibits the first step of the synthesis of thyroid hormone in the thyroid gland. Since thiocyanates compete with iodine transport into the thyroid follicular cells, where thyroid hormones are synthesized, they decrease the amount of thyroxine produced by the thyroid gland, which leads to hypothyroidism.

Many commonly eaten foods, especially in a vegan diet, contain thiocyanates. Too much dietary thiocyanates will dampen thyroid hormone function. For example: if your thyroid gland is already weak, excessive amounts of kale and other thiocyanate rich foods could lead to hypothyroidism.

Foods Containing Thiocyanates:

  • African yams (White Yams)
  • Alfalfa sprouts
  • Almonds
  • Apricot
  • Bok Choy
  • Bananas
  • Black Eyed Peas
  • Broccoli
  • Brussels sprouts
  • Buckwheat
  • Butter Beans
  • Cabbage
  • Carrot
  • Cashews
  • Cassava
  • Cauliflower
  • Cherry
  • Chickpeas
  • Collard Greens
  • Flaxseeds
  • Garbanzo Beans
  • Greens
  • Horseradish
  • Kale
  • Lentils
  • Lima Beans
  • Millet
  • Mustard greens
  • Peaches
  • Peanuts
  • Plantain
  • Plums
  • Raspberry
  • Rutabaga
  • Spelt Flour
  • Strawberry
  • Turnips

Should You Be Concerned About Thiocyanate Deficiency or Toxicity?

Though Thiocyanates have a dark side, they also have positive value for those with sickle cell anemia (SCA). African-Americans are genetically prone to SCA, a type of congenital type of deficiency anemia, referred to as “thiocyanate deficiency anemia.”

A diet composed mainly of refined carbohydrates, sugar, and saturated fats, and low in thiocyanate will aggravate SCA. Researchers found that a plant-based diet, rich in yams and cassava root, prevents SCA. Since yams are exceptionally rich in thiocyanates, when it comes to SCA, it is called the “Yam vitamin.”

Yams come from a different family of plants than sweet potatoes. Yams are in the Dioscoreaceae family. Japanese mountain potato is a type of yam and often eaten raw, grated over sashimi. Chinese, Japanese, and Koreans make a kind of noodle from yams. Jinenjo, a variety of Japanese yam, is an ingredient in soba noodles.

Cassava is from the asparagus family. It is a staple food of the Latin American diet where it is called yucca or manioc. Cassava root is so high in thiocyanate that it has to be cooked to reduce toxicity. Improper preparation of cassava leads to low thyroid and can even cause severe nerve damage.

Low Thyroid Slows Metabolism

Hypothyroidism often called “low thyroid,” is a medical condition caused by insufficient thyroid hormones. Thyroxine (T4) and liothyronine (T3) are the most active thyroid hormones. Both are used to treat low thyroid.

Common Signs and Symptoms of Hypothyroidism:

  • Dry, scaly, thick, coarse hair
  • Sensitivity to cold
  • Slow pulse
  • Fatigue
  • Hoarse voice
  • Slowed speech
  • Swollen thyroid gland
  • Weight gain
  • Constipation
  • Numbness in fingers or hands
  • Confusion
  • Depression, dementia
  • Headaches
  • Menstrual problems
    • If you have hypothyroidism, your metabolism runs down, and you slow to a crawl. Eating too many foods high in thiocyanate may worsen your condition.

      Cigarette Smoke and Thiocyanate

      Smoking cigarettes, and exposure to second-hand smoke increase thiocyanate level. Testing for thiocyanate in blood, urine, or saliva is an accurate way to measure toxic exposure to cigarette smoke. Though doctors do not typically use thiocyanate testing to determine excess levels caused from dietary sources, urine or saliva self-testing may alert you to toxic levels of thiocyanate.

      Bottom Line on Thiocyanate

      Get a blood test if you suspect you might have hypothyroidism. Cut back on thiocyanate foods if you know you already have hypothyroidism. If you are concerned about thiocyanate overload, get a urine test for iodine and thiocyanate.

      Dr. J. E. Williams


      Dr. Williams is a pioneer in integrative and functional medicine, the author of six books, and a practicing clinician with over 100,000 patient visits. His areas of interest include longevity and viral immunity. Formerly from San Diego, he now resides in Sarasota, Florida and practices at the Florida Integrative Medical Center. He teaches at NOVA Southeastern University and Emperor’s College of Oriental Medicine.

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      1. Interesting article. Any advice as to what a reasonable amount of these foods might be?

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