Impact of restricted phosphorus, calcium-adjusted diet on musculoskeletal and mental health in Hypophosphatasia

Context

Impairments in musculoskeletal and mental health are common in adults with Hypophosphatasia (HPP). Restricted phosphorus intake has been suggested to positively affect symptoms in HPP, but there is lack of interventional evidence.
Objective

To evaluate the impact of a phosphorus-restricted, calcium-adjusted diet on musculoskeletal and mental health in HPP.
Design

Prospective, non-controlled, single-center interventional study (NuSTEPS II).
Setting

Outpatients at the Osteology Department, University of Wuerzburg, Germany.
Participants

26 adults with established HPP diagnosis.
Intervention

Standardized diet with defined daily intake of phosphorus (1160-1240 mg/d) and calcium (870-930 mg/d) over 8 weeks.
Main Outcome Measures

Functional testing and patient-reported outcome measures.
Results

At 8 weeks, significant improvements were observed in usual gait speed (p=.028) and the chair-rise test (p=.019) while no significant changes were seen in the 6-minute walk test (p=.468) and the timed up-and-go test (p=.230). Pain was not significantly reduced according to visual analogue scale (VAS) (p=.061), pain subscale of the 36-Item Short-Form Health Survey (SF-36) (p=.346) and Pain Disability Index (p=.686). Further, there was a significant improvement in the SF-36 vitality subscale (p=.022) while all other subscales as well as the Lower Extremity Functional Scale (p=.670) and the Fatigue Assessment Scale (p=.392) did not change significantly. Adjustments of mineral intake were not associated with relevant alterations regarding the intake of energy and energy-supplying nutrients or body composition.
Conclusion

Adjusting phosphorus and calcium intake may positively affect individual symptoms in adults with HPP, but overall clinical effectiveness regarding major issues like pain and endurance appears limited.