Consuming whole eggs vs egg whites may increase muscle-protein synthesis

A study published in the American Journal of Clinical Nutrition suggests that people who consume 18 g of protein from whole eggs or from egg whites after engaging in resistance exercise may differ dramatically in how their muscles build protein during the post-workout period.

In the study, 10 young men engaged in a single bout of resistance exercise and then ate either whole eggs or egg whites containing 18 g of protein. The participants then received infusions of amino acids—stable-isotope-labeled leucine and phenylalanine. This allowed the scientists to maintain and precisely measure amino acid levels in participants’ blood and muscles. The eggs used for the study were also isotopically labeled with leucine. This allowed for precise tracking of where the food-derived amino acids ended up after participants ingested them.

The researchers took repeated blood and muscle biopsy samples to assess how the egg-derived amino acids were appearing in the blood and in protein synthesis in muscles before and after the resistance exercise and eating. The yolks also contain protein, along with key nutrients and other food components that are not present in egg whites.

The researchers found that eating whole egg or the egg whites resulted in about 60–70% of the amino acids being available in the blood, which would suggest that getting one’s protein from whole eggs or just egg whites makes no difference. However, when the researchers directly measured protein synthesis in the muscle, they found a very different response.

“We saw that the ingestion of whole eggs immediately after resistance exercise resulted in greater muscle-protein synthesis than the ingestion of egg whites,” said lead researchers Nicholas Burd, a University of Illinois professor of kinesiology and community health. “This work is showing that consuming egg protein in its natural matrix has a much greater benefit than getting isolated protein from the same source.”

Abstract