Then, the researchers took biopsies of the men’s muscles two and five hours later to measure something called their myofibrillar protein synthetic response, or the rate at which their protein fibers repaired themselves following the small tears caused by their workout.

They discovered that the whole egg consumption sparked significantly greater protein fiber repair and recovery than eating the egg whites did. And that’s important, since that process is key to building bigger and stronger muscles, explains study author Nicholas A. Burd, Ph.D., an exercise physiologist at the University of Illinois at Urbana-Champaign.

The researchers haven’t been able to pinpoint exactly what it was about the whole egg that triggered a greater muscle-building response, Burd says. But it may have to do with “food synergy,” or the theory that food components work together to elicit a greater protein synthesis response than simply eating protein alone.

Some possibilities in the whole egg? The yolk contains fats, including the omega-3 fatty acid DHA, vitamins, like vitamins A, D, E, and K, and minerals, like phosphorus and iron. (The egg whites, while matched in protein, lacked the nutrients of the whole egg).

“All of these non-protein food components may be helping dietary amino acids to support the post-workout muscle building response,” says Burd.

So what does this mean for you? Well, you already know that you should eat protein after your workout. But these findings suggest you might be better off eating real food than simply chugging a protein shake afterwards, since they tend to lack the other nutrients that can make up a whole-foods source of protein.