No Yolks, No Ham, Sam-I-Am
Back in the 1990's, the sewers ran yellow with discarded egg yolks. The specter of high, artery-clogging cholesterol had risen above the land and health-conscious citizens everywhere began discarding their yolks. Restaurants quickly caught on and started featuring so-called "power breakfasts" on their menus that were devoid of cholesterol and, ipso facto, nutrients, color, and flavor.
Bodybuilders adopted the habit, too, but they were more afraid of what the egg yolks could supposedly do to their abs rather than their hearts. The thinking was that eating fat made you fat, and egg yolks contain a substantial amount of it.
We know better today about the alleged drawbacks of eggs, but despite that tens of thousands of bodybuilders and fitness people still discard their egg yolks and restaurants still feature those stupid power breakfasts. Fitness people don't know why they do it, and if you ask them they'll no doubt mutter something about health, the same way anti-gluten people do when you ask them about that particular lemming-inspired dietary restriction.
Maybe fitness people need another reason to stop the egg-white madness. Thanks to researchers the University of Illinois and the University of Toronto, they now have one. Eating whole eggs – the yolk plus the white – leads to far greater protein synthesis than eating just the whites.
The scientists recruited 10 weight-trained men that were all 21 years old, give or take a year. Each of them received a continuous infusion of chemically labeled amino acids (to measure amino acid kinetics) while doing a short workout consisting of 4 sets of 10 reps on leg presses and leg extensions.
After the workout, the lifters received either whole eggs (also containing labeled amino acids) or egg whites. The whole eggs contained 18 grams of protein and 17 grams of fat, while the egg whites contained 18 grams of protein and 0 grams of fat.
The study involved a crossover trial, meaning all 10 men participated in both tests (whole eggs and egg whites post workout).
Blood samples and muscle biopsies revealed that the amino acid leucine got into the blood faster after eating egg whites, but overall the levels of leucine were the same in both groups during most of the 5-hour post-meal period.
However, the whole egg group experienced a greater surge in mTOR, which is probably the most important cell-signaling complex for muscle growth. The higher the levels of mTOR, the greater the synthesis of protein. (Three things generally stimulate mTOR naturally: mechanical stress, growth factors like IGF, growth hormone, insulin, etc., and amino acids.)
Most importantly, eating whole eggs increased post-exercise muscle protein synthesis about 45% more than plain egg whites.
While the researchers weren't sure why the whole eggs were so much more effective in growing muscle than just plain egg whites, they assumed it had something to do with the "extra nutritional food constituents" contained in whole eggs.
What this means is that there are most likely vitamins, minerals, phytonutrients, phenols, fats, etc., in whole eggs that are lacking in egg whites, and that all of them do a body good and result in additional muscle protein synthesis.
So stop plopping your egg yolks down the garbage disposal.
- van Vliet 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. 2017 Dec;106(6):1401-1412. PubMed.