How they build muscle: Not from being hurled by the dozen at your boss’s house. The protein in eggs has the highest biological value—a measure of how well it supports your body’s protein needs—of any food, including our beloved beef. “Calorie for calorie, you need less protein from eggs than you do from other sources to achieve the same muscle-building benefits,” says Volek.
But you have to eat the yolk. In addition to protein, it also contains vitamin B12, which is necessary for fat breakdown and muscle contraction. (And no, eating a few eggs a day won’t increase your risk of heart disease.)
How they keep you healthy: Eggs are vitamins and minerals over easy; they’re packed with riboflavin, folate, vitamins B6, B12, D, and E, and iron, phosphorus, and zinc.