Study analysis · Current Developments in Nutrition · 2025
Eating more protein won't make your shin bones stronger—here's what actually does.
Endurance athletes who eat more animal protein like meat and dairy have bigger calf muscles and slightly stronger spine bones, but not stronger leg bones.
Overview
What the study found
The study in plain English — the bottom line, every takeaway we extracted, and what to do with them.
In simple terms
This study looked at a group of runners and saw that those who ate more protein from meat and dairy tended to have slightly stronger bones and bigger muscles—but it didn’t change what they ate to see if that caused the difference. So it’s like noticing that people who wear running shoes often run faster—you can’t say the shoes make them faster, just that they often go together.
What’s the bottom line?
This study looked at runners and triathletes to see if eating more protein, especially from meat and dairy, helps their bones and muscles get stronger.
How strong is this study?
The researchers used good tools to measure bones and what people ate, which is great. But they only checked everyone once, didn’t change anyone’s diet, and didn’t have a big enough group to be super sure about their results. So while the study gives us a hint, we can’t trust it fully—it’s like guessing the weather from one cloudy day instead of checking the forecast for a whole week.
40 / 100
- COI disclosure+40/40
- Data availabilitydata not shared
- Code availabilitycode not shared
6 / 100
- Randomizationnot randomized
- Blindingblinding unclear
- Control groupno control group
- Sample size (n=50)+4.4/20
- Follow-upno follow-up reported
100 / 100
77 / 100
- P-values+15/15
- Effect size+20/20
- Confidence intervals+15/15
- Pre-registrationnot pre-registered
Each component is scored out of 100 and then capped by the study design — a case series cannot reach the ceiling a randomised trial can, however well it is reported.
Where it sits
RCT reviewsReviews of RCTs (Meta-analyses)
Max 100Randomized TrialsRandomized Trials
Max 90Reviews of Cohort StudiesReviews of Cohort Studies
Max 85Cohort StudiesCohort Studies
Max 72Reviews of Case-Control StudiesReviews of Case-Control Studies
Max 63Case-Control StudiesCase-Control Studies
Max 58Cross-Sectional & Case SeriesCross-Sectional & Case Series
Max 50Expert OpinionExpert Opinion
Max 544 / 100
Probability of being correct
Snapshots of a population at a single point in time, or descriptions of small groups. Can identify correlations and prevalence, but cannot determine cause and effect.
This design cannot establish causation — the findings describe an association, not a cause. This is a cross-sectional observational study with no randomization, no control group, and no manipulation of variables. It measures associations at a single point in time, making it impossible to determine if dietary protein causes changes in bone or muscle outcomes or if other factors (like overall diet, training, or genetics) are responsible.
No Conflicts
No conflicts of interest identified
No conflicts of interest or funding statements were disclosed in the study text. No industry ties, employment relationships, or funder involvement were identified.
The study was conducted at McGill University with ethics approval, but no funding sources, author affiliations with industry, or conflicts of interest were disclosed. The absence of a COI or funding statement limits transparency, but no evidence of bias or industry influence was found in the methodology or results.
Key takeaways
- 01
People who ate more animal protein had stronger shin bones (SSIp) and bigger calf muscles.
- 02
Total protein intake was linked to slightly higher spine bone density, but not to shin bone density or muscle strength.
- 03
The bone and muscle differences were small and likely due to bigger muscles from protein, not protein directly strengthening bones.
Surprising findings
- Total dietary protein showed no link to tibial bone strength (SSIp) or volumetric bone density, despite the tibia being the most loaded bone in runners.Everyone assumes more protein = stronger bones everywhere—but this study found zero correlation in the exact bone most vulnerable to stress fractures in endurance athletes.
- Animal protein correlated with higher cortical vBMD at the 66% tibia site (r = -0.34, p = 0.02)—but the sign was negative, suggesting a complex, possibly confounded relationship.A negative correlation with cortical density is counterintuitive—usually higher density is better. This hints that animal protein might be linked to structural changes we don’t fully understand yet.
Practical takeaways
Endurance athletes aiming to boost calf muscle size and spine bone density should prioritize animal protein sources like eggs, dairy, meat, and fish—especially if training over 40km/week.
This was a small, cross-sectional study—correlation doesn’t equal causation. Muscle mass was the real driver, not protein alone.
medium confidenceDon’t obsess over total protein grams—focus on getting enough animal protein (aim for 1.8–2.0 g/kg/day) to support muscle maintenance under high training loads.
If you’re vegan or plant-based, this doesn’t mean you’re at risk—just that animal protein showed stronger associations in this specific group.
medium confidenceWhy this study matters
Animal Protein = Bigger Calves
Animal-derived protein intake was strongly correlated with increased calf muscle cross-sectional area (r = 0.57, p < 0.001), even after adjusting for lean body mass, calcium, and training volume. This suggests animal proteins may uniquely support muscle maintenance under high training loads.
Most people think total protein is what matters—but this study shows the source (animal vs. plant) might be the real key for muscle growth in endurance athletes.
Spine Bones, Not Shins
Total protein intake explained 16% of the variance in lumbar spine aBMD (β = 0.398, p = 0.009), but showed NO association with tibial bone density or strength—despite the tibia being the bone most stressed by running.
Your spine benefits from protein, but your legs—where you actually run—don't. This flips the script on where nutrition matters most for athletes.
The Muscle-Bone Connection
The link between protein and bone strength disappeared after adjusting for lean body mass—meaning muscle size, not protein itself, likely drives bone strength. SSIp (bone strength) was only predicted by muscle mass, not protein intake.
It’s not the protein you eat—it’s the muscle you build from it. Protein’s real superpower might be building muscle, which then strengthens bones indirectly.
Want the whole report?
Detailed mode opens the full scientific breakdown — every score component, the methodology, conflicts of interest, the evidence analysis behind each claim, and the raw study data.
Overview
What the study found
The study in plain English — the bottom line, every takeaway we extracted, and what to do with them.
Not medical advice. For informational purposes only. Always consult a healthcare professional. Terms
This study looked at runners and triathletes to see if eating more protein, especially from meat and dairy, helps their bones and muscles get stronger.
Research results
People who ate more animal protein had stronger shin bones (SSIp) and bigger calf muscles. Total protein intake was linked to slightly higher spine bone density, but not to shin bone density or muscle strength.
What this means - more context
The bone and muscle differences were small and likely due to bigger muscles from protein, not protein directly strengthening bones.
This study examined whether dietary protein intake is associated with bone and muscle health in endurance-trained adults using advanced imaging (pQCT and DXA).
Total dietary protein intake showed no association with tibial volumetric bone density or muscle measures, but was linked to higher lumbar spine aBMD (explaining 16% of variance). Animal-derived protein correlated with greater tibial bone strength (SSIp) at 38% and 66% sites and increased calf muscle CSA, independent of lean mass, calcium, and training volume.
Methods Used
Cross-sectional study of 50 endurance-trained adults (19 female, 31 male); dietary protein intake assessed via 3-day 24-hour recalls; bone and muscle measures obtained using pQCT (tibia) and DXA (lumbar spine, femur); adjusted regression models controlled for lean body mass, calcium intake, and physical activity.
Main Finding
Total dietary protein intake was associated with higher lumbar spine aBMD (β = 0.398, P = 0.009), explaining approximately 16% of its variance after adjustments; animal protein intake correlated with tibial SSIp (r = 0.39–0.44) and calf muscle CSA (r = 0.57), but not with pQCT bone density measures.
Confidence Level
Moderate; findings are statistically significant but limited by cross-sectional design, small sample size, and inability to infer causality; effect sizes are modest and confounded by lean body mass.
Study Flags
Red Flags
- •Cross-sectional design (cannot prove cause-effect)
- •Small sample size (n=50) with limited power for subgroup analyses
- •Dietary intake self-reported via recalls (prone to error)
Surprising Findings
Total dietary protein showed no link to tibial bone strength (SSIp) or volumetric bone density, despite the tibia being the most loaded bone in runners.
Everyone assumes more protein = stronger bones everywhere—but this study found zero correlation in the exact bone most vulnerable to stress fractures in endurance athletes.
Practical Takeaways
Endurance athletes aiming to boost calf muscle size and spine bone density should prioritize animal protein sources like eggs, dairy, meat, and fish—especially if training over 40km/week.
RCT reviewsReviews of RCTs (Meta-analyses)
Max 100Randomized TrialsRandomized Trials
Max 90Reviews of Cohort StudiesReviews of Cohort Studies
Max 85Cohort StudiesCohort Studies
Max 72Reviews of Case-Control StudiesReviews of Case-Control Studies
Max 63Case-Control StudiesCase-Control Studies
Max 58Cross-Sectional & Case SeriesCross-Sectional & Case Series
Max 50Expert OpinionExpert Opinion
Max 544 / 100
Probability of being correct
Snapshots of a population at a single point in time, or descriptions of small groups. Can identify correlations and prevalence, but cannot determine cause and effect.
Human Cross-Sectional
Subject
Moderate probability
on the GRADE evidence scale
This study looked at a group of runners and saw that those who ate more protein from meat and dairy tended to have slightly stronger bones and bigger muscles—but it didn’t change what they ate to see if that caused the difference. So it’s like noticing that people who wear running shoes often run faster—you can’t say the shoes make them faster, just that they often go together.
No conflicts of interest were detected in this study. No score impact.
Strengths
- Used advanced imaging (pQCT and DXA) to measure bone and muscle properties with high precision
- Used validated dietary assessment tool (ASA24) with multiple 24-hour recalls
- Adjusted analyses for key confounders (sex, lean body mass, physical activity, calcium intake)
Weaknesses
- Cross-sectional design prevents causal inference
- No randomization or control group
- Small sample size limits statistical power for subgroup analyses
Methodology
Evidence Keywords
Statistical Reporting
Not medical advice. For informational purposes only. Always consult a healthcare professional. Terms
This study looked at runners and triathletes to see if eating more protein, especially from meat and dairy, helps their bones and muscles get stronger.
Research results
People who ate more animal protein had stronger shin bones (SSIp) and bigger calf muscles. Total protein intake was linked to slightly higher spine bone density, but not to shin bone density or muscle strength.
What this means - more context
The bone and muscle differences were small and likely due to bigger muscles from protein, not protein directly strengthening bones.
This study examined whether dietary protein intake is associated with bone and muscle health in endurance-trained adults using advanced imaging (pQCT and DXA).
Total dietary protein intake showed no association with tibial volumetric bone density or muscle measures, but was linked to higher lumbar spine aBMD (explaining 16% of variance). Animal-derived protein correlated with greater tibial bone strength (SSIp) at 38% and 66% sites and increased calf muscle CSA, independent of lean mass, calcium, and training volume.
Methods Used
Cross-sectional study of 50 endurance-trained adults (19 female, 31 male); dietary protein intake assessed via 3-day 24-hour recalls; bone and muscle measures obtained using pQCT (tibia) and DXA (lumbar spine, femur); adjusted regression models controlled for lean body mass, calcium intake, and physical activity.
Main Finding
Total dietary protein intake was associated with higher lumbar spine aBMD (β = 0.398, P = 0.009), explaining approximately 16% of its variance after adjustments; animal protein intake correlated with tibial SSIp (r = 0.39–0.44) and calf muscle CSA (r = 0.57), but not with pQCT bone density measures.
Confidence Level
Moderate; findings are statistically significant but limited by cross-sectional design, small sample size, and inability to infer causality; effect sizes are modest and confounded by lean body mass.
Study Flags
Red Flags
- •Cross-sectional design (cannot prove cause-effect)
- •Small sample size (n=50) with limited power for subgroup analyses
- •Dietary intake self-reported via recalls (prone to error)
Surprising Findings
Total dietary protein showed no link to tibial bone strength (SSIp) or volumetric bone density, despite the tibia being the most loaded bone in runners.
Everyone assumes more protein = stronger bones everywhere—but this study found zero correlation in the exact bone most vulnerable to stress fractures in endurance athletes.
Practical Takeaways
Endurance athletes aiming to boost calf muscle size and spine bone density should prioritize animal protein sources like eggs, dairy, meat, and fish—especially if training over 40km/week.
RCT reviewsReviews of RCTs (Meta-analyses)
Max 100Randomized TrialsRandomized Trials
Max 90Reviews of Cohort StudiesReviews of Cohort Studies
Max 85Cohort StudiesCohort Studies
Max 72Reviews of Case-Control StudiesReviews of Case-Control Studies
Max 63Case-Control StudiesCase-Control Studies
Max 58Cross-Sectional & Case SeriesCross-Sectional & Case Series
Max 50Expert OpinionExpert Opinion
Max 544 / 100
Probability of being correct
Snapshots of a population at a single point in time, or descriptions of small groups. Can identify correlations and prevalence, but cannot determine cause and effect.
Human Cross-Sectional
Subject
Moderate probability
on the GRADE evidence scale
This study looked at a group of runners and saw that those who ate more protein from meat and dairy tended to have slightly stronger bones and bigger muscles—but it didn’t change what they ate to see if that caused the difference. So it’s like noticing that people who wear running shoes often run faster—you can’t say the shoes make them faster, just that they often go together.
No conflicts of interest were detected in this study. No score impact.
Strengths
- Used advanced imaging (pQCT and DXA) to measure bone and muscle properties with high precision
- Used validated dietary assessment tool (ASA24) with multiple 24-hour recalls
- Adjusted analyses for key confounders (sex, lean body mass, physical activity, calcium intake)
Weaknesses
- Cross-sectional design prevents causal inference
- No randomization or control group
- Small sample size limits statistical power for subgroup analyses
Methodology
Evidence Keywords
Statistical Reporting
Scoring
How strong is this study?
The researchers used good tools to measure bones and what people ate, which is great. But they only checked everyone once, didn’t change anyone’s diet, and didn’t have a big enough group to be super sure about their results. So while the study gives us a hint, we can’t trust it fully—it’s like guessing the weather from one cloudy day instead of checking the forecast for a whole week.
40 / 100
- COI disclosure+40/40
- Data availabilitydata not shared
- Code availabilitycode not shared
6 / 100
- Randomizationnot randomized
- Blindingblinding unclear
- Control groupno control group
- Sample size (n=50)+4.4/20
- Follow-upno follow-up reported
100 / 100
77 / 100
- P-values+15/15
- Effect size+20/20
- Confidence intervals+15/15
- Pre-registrationnot pre-registered
Each component is scored out of 100 and then capped by the study design — a case series cannot reach the ceiling a randomised trial can, however well it is reported.
Where it sits
RCT reviewsReviews of RCTs (Meta-analyses)
Max 100Randomized TrialsRandomized Trials
Max 90Reviews of Cohort StudiesReviews of Cohort Studies
Max 85Cohort StudiesCohort Studies
Max 72Reviews of Case-Control StudiesReviews of Case-Control Studies
Max 63Case-Control StudiesCase-Control Studies
Max 58Cross-Sectional & Case SeriesCross-Sectional & Case Series
Max 50Expert OpinionExpert Opinion
Max 544 / 100
Probability of being correct
Snapshots of a population at a single point in time, or descriptions of small groups. Can identify correlations and prevalence, but cannot determine cause and effect.
This design cannot establish causation — the findings describe an association, not a cause. This is a cross-sectional observational study with no randomization, no control group, and no manipulation of variables. It measures associations at a single point in time, making it impossible to determine if dietary protein causes changes in bone or muscle outcomes or if other factors (like overall diet, training, or genetics) are responsible.
No Conflicts
No conflicts of interest identified
No conflicts of interest or funding statements were disclosed in the study text. No industry ties, employment relationships, or funder involvement were identified.
The study was conducted at McGill University with ethics approval, but no funding sources, author affiliations with industry, or conflicts of interest were disclosed. The absence of a COI or funding statement limits transparency, but no evidence of bias or industry influence was found in the methodology or results.
Standing
Who’s using this study?
The videos and claims on this site that lean on this study, and the researchers who wrote it.
1 video from Shawn Baker MD cite this study, drawing 1 claim from it.
- Very strong evidence
Randomized or controlled trials support this claim, alongside consistent supporting evidence.
Evidence
Authored by
7 researchersIf this is your work, this is how we attribute it on Fit Body Science. Silar Gardy is listed as the lead author.