The good & bad of kale

As in most things, balance is needed. Kale & related foods are nutritious & many reduce the risk of cancer.

http://commonhealth.wbur.org/2014/01/the-dark-side-of-kale-and-how-to-eat-around-it

January 10, 2014 | 2:36 PM | Rachel Zimmerman

-----

Writing for The Times, Jennifer Berman reports on the dark side of kale, and how the health-infused, veggie Eden she’d carefully built over years began to crumble:

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.

My first reaction: Berman must be misguided, mistaken. Can kale possibly be bad?

Well, yes, possibly. Here’s the science-y low-down on the kale-thyroid connection from the Oregon State University Micronutrient Information site:

Very high intakes of cruciferous vegetables…have been found to cause hypothyroidism (insufficient thyroid hormone) in animals (68). There has been one case report of an 88-year-old woman developing severe hypothyroidism and coma following consumption of an estimated 1.0 to 1.5 kg/day of raw bok choy for several months. Two mechanisms have been identified to explain this effect. The hydrolysis of some glucosinolates found in cruciferous vegetables (e.g., progoitrin) may yield a compound known as goitrin, which has been found to interfere with thyroid hormone synthesis. The hydrolysis of another class of glucosinolates, known as indole glucosinolates, results in the release of thiocyanate ions, which can compete with iodine for uptake by the thyroid gland. Increased exposure to thiocyanate ions from cruciferous vegetable consumption or, more commonly, from cigarette smoking, does not appear to increase the risk of hypothyroidism unless accompanied by iodine deficiency. One study in humans found that the consumption of 150 g/day (5 oz/day) of cooked Brussels sprouts for four weeks had no adverse effects on thyroid function.

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, confirms the kale-thyroid link. But, she says, “normal, reasonable amounts of eating should not be a problem. A regular person [with no thyroid issues] who eats several servings of cruciferous vegetables a week should not have problems.”

Fung adds: “It’s the dose that makes a poison. 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.”