The answer: Bone!
"Cooking with the bone in has at least one advantage—besides the meat, you’ll also be eating the marrow in the bone cavity," says The Paleo Diet author Loren Cordain, Ph.D., of Colorado State University.
And this is a good thing because...? “About 70% of bone marrow’s calories are healthy monounsaturated fatty acids that can lower cholesterol and reduce the risk for heart disease,” says Cordain. And, she adds, while meat alone contains no vitamin A, which is needed for healthy vision, a strong immune system, and cell health, marrow’s packed with it.
As for how the marrow actually gets into the dish, it depends on what you’re making, Cordain says. “If the marrow’s exposed”—e.g., if you break the bone before you cook the meat—“its juices can flow into the dish.” Some people also make broth by roasting bones and then simmering them in a pot with vegetables. Yum.