Yucca

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One word: Cyanide! This root vegetable, a staple of South American cuisine, is packed with vitamins and minerals. But it's also hiding a sneaky, potentially lethal ingredient. The leaves and roots of raw yucca contain cyanogenic glycosides, chemicals that release cyanide when eaten. Yucca is still edible, but make sure you wash it thoroughly, rinse it, peel it, and cook it before consumption.