The best choice of protein source for building muscle is, without question, a hot topic in Sport Nutrition. Sport scientists, dieticians and nutritionists alike are often posed the following two questions:
Do proteins from dairy, meat, and plant sources differ in their capacity to promote muscle growth during resistance exercise training?
And if so, which is best?
Before we answer these questions let's discuss the best approach to tackling these questions.
A look inside the laboratory
The best science behind the most effective protein source for building muscle is based on data generated from carefully controlled and somewhat sophisticated laboratory studies. These studies usually involve strength-trained volunteers ingesting a single source of protein soon after a one-off weight-lifting workout. Simultaneously, skilled researchers apply what is called “stable isotopic tracer methodology”. This technique involves slowly pumping labelled (or “heavy”) isotopes consisting of synthetic amino acids directly into one forearm vein, serial blood sampling from the other and the collection of muscle biopsies, usually from the easily accessible vastus lateralis muscle. With access to specialized analytical instruments, not to mention technical expertise, this laboratory approach allows for the determination of muscle protein synthesis (MPS) — the “gold standard” for measuring the muscle building response to a given protein source.
What does the science tell us?
Animal sources of protein are often touted as more effective for muscle building than plant proteins. Consistent with this idea, laboratory studies have reported a greater post workout response of MPS when strength-trained young men consumed either skimmed milk or whey protein vs. a matched dose of soy protein [1, 2]. As further proof that animal proteins trump plant proteins, a study in middle-aged men revealed a greater stimulation of MPS at rest after ingesting a 100g (4 oz) lean beef steak vs. a soy protein marketed and sold as a bona-fide replacement for beef. Plus, in healthy older adults, ingesting 35 grams of micellar casein protein stimulated a greater MPS response compared with a matched dose of the cereal protein, wheat. So, what makes the dairy proteins and beef more potent than soy and wheat in terms of stimulating MPS? And is it all bad news for the vegetarian/vegan strength-based athlete?