If you're a daily juicer and have a habit of throwing a certain leafy green superfood in your Vitamix, you might want to put down that leaf of kale. At least until after you read this.
A recent piece in the New York Times titled, "Kale? Juicing? Trouble Ahead," has called some attention to a potential downside to eating large amounts of what's become one of the health food world's most en vogue items. As it turns out, eating (or drinking) kale on a daily basis can cause hypothyroidism, or underactive thyroid. And kale isn't the only culprit.
The article, written by Jennifer Berman, explains how a Whole Foods junkie found her health comprised by one of the very foods she thought was doing her body good:
Imagine my shock, then, at my last physical, when my doctor told me I had hypothyroidism, common in women over 40. When I got home I looked up the condition on the Internet and found a list of foods to avoid. Kale, which I juiced every morning, tops the list, followed by broccoli, cauliflower, cabbage, Brussels sprouts and collard greens -- the cruciferous vegetables I consumed in large quantities because they are thought to prevent cancer, which runs in my family. And flax -- as in the seeds -- high in omega 3's, that I sprinkled on cereal and blended in strawberry almond milk smoothies. Also forbidden: almonds and strawberries, not to mention soy, peaches, peanuts, corn, radishes, rutabaga and spinach.
And it's true, according to The Linus Pauling Institute Micronutrient Information Center, very high intakes of cruciferous vegetables (such as kale, broccoli, and brussel sprouts) can cause hypothyroidism. In one case, an 88-year-old woman developed severe hypothyroidism and coma after eating an estimated 1.0 to 1.5 kg a day of raw bok choy for several months.
Teresa Fung, Sc.D., M.S.. an adjunct professor of nutrition at the Harvard School of Public Health and a professor at Simmons College in Boston, confirmed the link between kale and hypothyroidism. But she also pointed out that normal consumption shouldn't be a problem -- as in eating several servings a week, not a day.
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"It's the dose that makes a poison," Fung told Common Health. "If people have hypothyroidism or they're taking thyroid medication, then they should check with their doctor. But even in this case, reasonable amounts shouldn't be a problem. Now, if people have a tall glass of kale juice every single day, then it gets into the unknown territory."
Symptoms of hypothyroidism include everything from fatigue, dry skin, weight gain and muscle weakness, to pain and stiffness in the joints, thinning hair, depression, and impaired memory.