The Study
Habituation to low or high protein intake does not modulate basal or postprandial muscle protein synthesis rates: a randomized trial.
This study gave two groups of older men different amounts of protein for two weeks, then measured how their muscles used the protein after eating. It shows that how much protein you eat regularly might change how your body absorbs it, but not how fast your muscles grow. We can't say one diet is better — just that the muscle growth was about the same.
Analysis score
Maximum 90 for a randomized controlled trial.
Where the score came from
Scientists gave older men two different protein diets for two weeks and then fed them a protein shake to see if eating less protein made their muscles respond better.
Where does this study sit?
Reviews of RCTs (Meta-analyses)
Max 100Randomized Trials
Max 90Reviews of Cohort Studies
Max 85Cohort Studies
Max 72Reviews of Case-Control Studies
Max 63Case-Control Studies
Max 58Cross-Sectional & Case Series
Max 50Expert Opinion
Max 566 / 100
Quality score
Participants are randomly assigned to treatment or control groups, minimizing bias. The gold standard for testing whether an intervention causes an effect.
Key takeaways
Summary
Based on the study abstract and findings.
- 1Even though more amino acids were available in the blood with low protein intake, muscles didn't use them to build more protein — suggesting the body can't boost muscle growth beyond a certain protein dose, even if it's more efficient at absorbing it.
- 2After eating the same 25g protein shake, men who ate less protein had 5% more amino acids in their blood, but their muscles built new protein at the same rate (0.06% per hour) as those who ate more protein.
Score breakdown, methodology, conflicts of interest, evidence analysis & raw study data
Publication
Journal
The American journal of clinical nutrition
Year
2017
Authors
S. Gorissen, A. Horstman, R. Franssen, I. W. Kouw, B. Wall, N. Burd, L. D. de Groot, L. V. van Loon
Related Content
Claims (6)
In healthy older men, consuming 25 grams of whey protein raises the rate of muscle protein synthesis from 0.035% per hour to 0.060% per hour after eating, regardless of whether they had been eating low or high amounts of protein over the previous 14 days.
Among healthy older men, consuming either 0.7 or 1.5 grams of protein per kilogram of body weight daily for two weeks results in the same baseline rate of muscle protein synthesis.
In healthy older men, eating less protein for 14 days raises the amount of amino acids in the blood after a meal by about 5 percentage points compared to eating more protein, but it does not change the rate at which muscle protein is made after consuming whey protein.
In healthy older men, consuming 25 grams of whey protein after a meal increases muscle protein synthesis at a rate of 0.025% to 0.030% per hour, and this rate does not increase even if they consumed more protein over the previous 14 days.
In healthy older men, eating 0.7 grams of protein per kilogram of body weight per day for 14 days results in higher levels of dietary phenylalanine in the blood after meals compared to eating 1.5 grams per kilogram per day.
When total calorie intake is held constant, consuming more protein leads to greater muscle protein synthesis and less fat storage compared to consuming less protein.
Not medical advice. For informational purposes only. Always consult a qualified healthcare professional before making health decisions.