Harvard Health Letter

Where the worst type of fat is hiding in supermarket foods

Trans fats are undeniably bad for health, and they're still in many foods.

nutrition label grocery shopping fat
Image: GPointsStudio/Thinkstock

Lurking on supermarket shelves, within colorful, seemingly harmless packages, is something that can cause serious harm to your health: trans fat. "No amount of trans fat is acceptable, from a health standpoint," says registered dietitian Kathy McManus, director of the Department of Nutrition at Harvard-affiliated Brigham and Women's Hospital.

About trans fat

Trans fats in the diet come mostly from partially hydrogenated oils. They're made by a process that uses hydrogen gas to turn vegetable oils into solids. This new form of fat extends a food's shelf life and improves flavor and texture. It's been a mainstay in processed foods—such as pastries, crackers, margarine, and corn chips—for decades.

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