Vox:

"Mars and [other chocolate companies] made a conscious decision to invest in science to transform the image of their product from a treat to a health food," said New York University nutrition researcher Marion Nestle (no relation to the chocolate maker). "You can now sit there with your [chocolate bar] and say I'm getting my flavonoids."

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But despite the industry effort to date, cocoa still has never been proven to carry any long-term health benefits. And when it's delivered with a big dose of fat and sugar, any potential health perks are very quickly outweighed by chocolate's potential harm to the waistline.