When the weather service issues a winter storm warning, folks stock up on essentials. This often leads to a shortage of certain supermarket items — say, toilet paper, water, milk, bread and eggs. But in recent years, weather-worried grocery shoppers in a number of cities have reported a shortage of kale. The leafy green is so popular in places such as New York City and Portland, Ore., shoppers report that it’s nearly impossible to find the superfood even before the first snowfall.

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Kale, a cruciferous vegetable rich in polyphenols and high in fiber, has become a staple of a healthy diet (even in warmer weather). However, the hardy, healthy green has suffered a setback. This year’s report from the Environmental Working Group, author of the annual Dirty Dozen list on pesticide residue in fruits and veggies, says that after strawberries and spinach, kale has highest levels of pesticide residue of all produce sold in U.S. supermarkets.

According to the report, 92% of conventionally grown kale samples tested by the U.S. Department of Agriculture had traces of two or more pesticides. Some had as many as 18! Certain types of these pesticides have been linked to cancer, autism, attention-deficit hyperactivity disorder and Alzheimer’s disease.

If you want to keep eating kale — and you should — consider buying organic. But organic or not, thoroughly wash your produce. Some chefs and foodies recommend making an ice-water bath to soak kale leaves for a little while. Pour out the dirty water and soak them again; then give your precious greens a quick rinse! Hail kale!

Mehmet Oz, M.D., is host of “The Dr. Oz Show,” and Mike Roizen, M.D., is chief wellness officer and chairman of Wellness Institute at Cleveland Clinic.