The Study
Bone mineral density in French adults with early-treated phenylketonuria.
This study looked at a group of adults with PKU and noticed that those who stayed on their special diet longer tended to have weaker bones. But it didn’t change anyone’s diet to see what would happen — it just observed what was already going on. So we can’t say the diet made their bones weak — just that the two things happened together.
Analysis score
Maximum 44 for a cross-sectional study.
Where the score came from
People with PKU must eat a special low-protein diet and take amino acid supplements to stay healthy. But this study found that those who stayed on this diet their whole life sometimes ended up with weaker bones.
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 544 / 100
Quality score
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.
Key takeaways
Summary
Based on the study abstract and findings.
- 1Yes — 1 in 9 adults with PKU had bone density low enough to increase fracture risk, and it was tied to modern lifelong diet recommendations.
- 211.4% of adults had very low bone density (Z-score ≤ -2).
- 3Those with weak bones had lower body weight and ate more amino acid supplements (0.80 g/kg/day vs.
- 40.53 g/kg/day).
- 5People born after 1990 who never stopped the diet had 4.7 times higher risk.
Score breakdown, methodology, conflicts of interest, evidence analysis & raw study data
Publication
Journal
Molecular genetics and metabolism
Year
2025
Authors
Elisa Dybal, F. Maillot, F. Feillet, Alain Fouilhoux, Leonardo Astudillo, Christian Lavigne, J. Arnoux, S. Odent, Claire Gay, Manuel Schiff, K. Mazodier, Alice Kuster, Vincent Rigalleau, Christel Thauvin-Robinet, V. Leguy-Seguin, Claire Douillard, Sybil Charrière
Related Content
Claims (6)
People who consume more dietary protein, including from animal sources, have higher bone mineral density.
Among French adults with early-treated phenylketonuria, those with low bone mineral density have a lower body mass index and consume more amino acid supplements daily than those with normal bone mineral density.
French adults with phenylketonuria who followed a low-protein diet their entire lives after 1990 have lower bone mineral density than those who stopped the diet.
In French adults who were treated early for phenylketonuria, the average bone density is below the normal range for their age, and about 1 in 9 have bone density low enough to be considered clinically significant.
In French adults with early-treated phenylketonuria, consuming more total protein, especially from amino acid supplements, is linked to lower bone mineral density.
In French adults with early-treated phenylketonuria, long-term use of a low-protein diet with amino acid supplements is linked to a 4.7 times higher risk of low bone mineral density, affecting 11.4% of patients, with those affected consuming more amino acid supplements than those without low bone density.
Not medical advice. For informational purposes only. Always consult a qualified healthcare professional before making health decisions.