Dietary protein distribution positively influences 24-h muscle protein synthesis in healthy adults.
Level 2 - randomized trial
Individual randomized crossover metabolic feeding trial
PubMed 24477298 · doi:10.3945/jn.113.185280
What was done
Eight healthy adult men and women (age 36.9 ± 3.1 years, BMI 25.7 ± 0.8 kg/m²) participated in a 7-day crossover feeding study with a 30-day washout period. Participants received isoenergetic, isonitrogenous diets with daily protein distributed evenly across meals (EVEN: ~31.5 g at breakfast, 29.9 g at lunch, 32.7 g at dinner) or skewed toward dinner (SKEW: ~10.7 g at breakfast, 16.0 g at lunch, 63.4 g at dinner). Mixed muscle protein fractional synthesis rate (FSR) was measured over 24-hour periods on day 1 and day 7 using L-[ring-¹³C₆]phenylalanine infusion and vastus lateralis muscle biopsies.
What was found
The 24-hour mixed muscle protein fractional synthesis rate was 25% higher on the EVEN diet (0.075 ± 0.006%/h) compared to the SKEW diet (0.056 ± 0.006%/h; P = 0.003). This difference persisted after 7 days of dietary habituation (EVEN: 0.077 ± 0.006%/h vs. SKEW: 0.056 ± 0.006%/h; P = 0.001).
Why it matters
These findings indicate that consuming moderate amounts of protein (~30 g) at each meal stimulates 24-hour muscle protein synthesis more effectively than consuming the majority of daily protein at dinner.
Limits
The sample size was very small (n = 8). The trial measured acute 24-hour fractional synthesis rates over a 7-day period rather than long-term changes in muscle mass, strength, or functional outcomes. Findings in healthy young-to-middle-aged adults may not generalize to older individuals, athletes, or clinical populations.
Cited by
- supports Consuming protein across three to four evenly spaced meals containing 25 to 30 grams or more optimizes 24-hour muscle protein synthesis.
- context NHANES dietary survey data indicates that in the United States, protein intake is skewed towards the evening meal, with Americans consuming about three times as much protein at dinner compared to breakfast or lunch.