In nutrition science, individual nutrients are often recognized for their specific roles in physiology. We know that calcium is critical for bone health, choline is important for brain development and a lack of vitamin C will result in scurvy. However, whole foods are complex and contain numerous compounds, often leading to effects that extend beyond the sum of their parts.
This was seen in a recent study published in The American Journal of Clinical Nutrition. Researchers examined the effects of whole egg consumption compared to an isonitrogenous amount of egg whites in healthy young men following exercise. They found that, despite containing the same amount of protein (16 grams), whole eggs resulted in significantly greater muscle protein synthesis versus egg whites.
Egg whites have long been a favorite of athletes and fitness professionals due to their high-quality protein content. The white fraction of one large egg contains 3.6 grams of protein and 17 calories. However, the overwhelming majority of essential vitamins and minerals reside in the yolk, including choline, selenium, and the antioxidants lutein and zeaxanthin. Egg yolks also contain 4.5 grams of fat per large egg, most of which is unsaturated. In addition to the traditional nutrition components, there are a number of bioactive compounds in the yolk, many of which have yet to be characterized.
Which or how many of these components are important in stimulating muscle protein synthesis remains to be determined. As is always the case with nutrition science, more research is needed.
Reference: Vilet S, et al. Consumption of whole eggs promotes greater stimulation of postexercise muscle protein synthesis than consumption of isonitrogenous amounts of egg whites in young men. Am J Clin Nutr. E-pub ahead of print.