Don't ditch those egg yolks...
Many of you have heard me go on and on about my love (or hatred) for eggs. I eat several (4 or 5) scrambled eggs every single day (at least Monday thru Friday), much to my chagrin. Growing up I absolutely hated eggs, but forced myself to tolerate them as I continually read about how heathy and beneficial they are to overall health as well as muscle building and performance. Even to this day, my kids ask me, "Why do you eat eggs if you don't like them?" Well, there should be plenty of things that you do in your life that isn't necessarily high up on your favourites list. Think of food as fuel, not always a reward...
Anyways, I am constantly encouraging everyone to try and squeeze eggs into their diet - the whole egg that is. Yolk included. A study I cam across from 2017 further backs up this notion:
Background: Protein in the diet is commonly ingested from whole foods that contain various macro- and micronutrients. However, the effect of consuming protein within its natural whole-food matrix on postprandial protein metabolism remains understudied in humans.Objective: We aimed to compare the whole-body and muscle protein metabolic responses after the consumption of whole eggs with egg whites during exercise recovery in young men.Design: In crossover trials, 10 resistance-trained men [aged 21 ± 1 y; 88 ± 3 kg; body fat: 16% ± 1% (means ± SEMs)] received primed continuous l-[ring-2H5]phenylalanine and l-[1-13C]leucine infusions and performed a single bout of resistance exercise. After exercise, participants consumed intrinsically l-[5,5,5-2H3]leucine-labeled whole eggs (18 g protein, 17 g fat) or egg whites (18 g protein, 0 g fat). Repeated blood and muscle biopsy samples were collected to assess whole-body leucine kinetics, intramuscular signaling, and myofibrillar protein synthesis.Results: Plasma appearance rates of protein-derived leucine were more rapid after the consumption of egg whites than after whole eggs (P = 0.01). Total plasma availability of leucine over the 300-min postprandial period was similar (P= 0.75) between the ingestion of whole eggs (68% ± 1%) and egg whites (66% ± 2%), with no difference in whole-body net leucine balance (P = 0.27). Both whole-egg and egg white conditions increased the phosphorylation of mammalian target of rapamycin complex 1, ribosomal protein S6 kinase 1, and eukaryotic translation initiation factor 4E-binding protein 1 during postexercise recovery (all P < 0.05). However, whole-egg ingestion increased the postexercise myofibrillar protein synthetic response to a greater extent than did the ingestion of egg whites (P= 0.04).Conclusions: We show that the ingestion of whole eggs immediately after resistance exercise resulted in greater stimulation of myofibrillar protein synthesis than did the ingestion of egg whites, despite being matched for protein content in young men. Our data indicate that the ingestion of nutrient- and protein-dense foods differentially stimulates muscle anabolism compared with protein-dense foods.
Leucine is the one word you see pop up a number of times in that abstract. Leucine is an essential amino acid - meaning our bodies cannot synthesize it, we must obtain it from our diet. But more importantly than that, Leucine is one of the most important, if not the most important amino acid for muscle protein synthesis (building muscle). Eggs certainly aren't the only source of Leucine, but they are a tremendous source of it.
Back to the study. What I found so intriguing/impressive about this study, is that the net protein ingested was standardized between both the whole-egg and egg-white groups. In other words, they both ingested the same amount of protein (18g) following their workout. Despite the same amount of protein ingested in both groups, the whole-egg group saw a greater stimulation of muscular growth when compared to the egg-white only group.
By the way, dietary cholesterol from dietary sources such as eggs is not an inherently dangerous endeavour. The research surrounding an elevation of cholesterol through dietary means is weak. In fact, our bodies produce far more cholesterol in our livers that what most people consume on a day to day basis. I get into this in far greater detail on Day 12 of my 30-Day Nutrition Bootcamp, so if you'd like to discuss this in greater detail, you can come speak to me or join the next round of the Nutrition Bootcamp when it comes up.
As with any study, there are further discussions to be had surrounding the ingestion of whole-eggs, and how or why there is a greater stimulation of muscle protein synthesis, but for now, it appears as though the research is telling you to eat the whole eggs rather than just the egg whites if your goal is to improve strength and build some muscle.
B.Sc., CSCS, CCFT