A moderate serving of high-quality protein maximally stimulates skeletal muscle protein synthesis in young and elderly subjects.
Level 2 - randomized trial
Randomized controlled trial evaluating acute postprandial muscle protein synthesis responses.
PubMed 19699838 · doi:10.1016/j.jada.2009.06.369
What was done
Healthy young (n=17, age 34±3 years) and elderly (n=17, age 68±2 years) subjects consumed either a moderate serving (113 g; 220 kcal; 30 g protein) or a large serving (340 g; 660 kcal; 90 g protein) of 90% lean beef. Mixed muscle fractional synthesis rate was measured from vastus lateralis biopsy and venous blood samples during a primed, constant infusion of L-[ring-13C6] phenylalanine over a 3-hour postabsorptive baseline and 5 hours postprandially.
What was found
A 113 g serving of lean beef increased muscle protein synthesis by approximately 50% in both young and older volunteers. Despite a threefold increase in protein and energy content, ingestion of 340 g lean beef produced no further increase in muscle protein synthesis in either group.
Why it matters
These findings suggest that approximately 30 g of high-quality protein maximally stimulates acute skeletal muscle protein synthesis in a single meal, with no additive acute anabolic response from tripling the portion size.
Limits
Small sample size (n=34 total across two age groups). The study only assessed acute 5-hour mixed muscle protein synthesis after a single meal type (lean beef), without evaluating doses between 30 g and 90 g, whole-body protein breakdown, or long-term muscle mass and functional outcomes.
Cited by
- contradicts Consuming 30 grams of beef protein alone stimulates more muscle protein synthesis than consuming 70 grams of beef protein as part of a mixed meal with carbohydrates and vegetables.