Old Rule: Avoid red meat.
New Rule: Beef in moderation can be healthy.
Red meat was long considered a heart attack on a plate because it's high in saturated fat. But a 2010 study from the Harvard School of Public Health found that the cardiovascular risk comes from processed varieties, such as sausage, hot dogs, and cold cuts—not from steak, hamburgers, and other nonprocessed cuts. (The real culprits may be salt and preservatives). Red meat is a good source of iron and immunity-boosting zinc—two nutrients some women don't get enough of. Beef (especially grass-fed) also contains high concentrations of conjugated linoleic acid, a type of fat that may decrease cancer risk and help reduce body fat.
"But not all red meats are created equal," says Leslie J. Bonci, director of sports nutrition at the University of Pittsburgh's Center for Sports Medicine. She recommends choosing very lean cuts and avoiding anything labeled "prime," as it will have more fat marbling. And try not to eat more than three 4- to 5-ounce servings (about the size of an iPhone) per week.