Dietary Intake Modifications to Protect Against Changes in Bone Metabolism

Study Overview
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Brief Summary
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Bone loss is not only a well-documented effect of spaceflight on astronauts, but also a condition that affects millions of men and women on Earth each year. Many countermeasures to bone loss have been proposed, and many have been evaluated to some degree. To date, those showing potential have focused on either exercise or pharmacological interventions, but none have targeted dietary intake alone as a factor to predict or minimize bone loss during spaceflight. The investigators proposed to document how the ratio of acid precursors to base precursors in the diet is related to directional changes in markers of bone resorption and formation during flight and recovery from flight. There is a high likelihood for success in predicting the extent of bone loss from dietary intake patterns of astronauts during spaceflight, given that this concept is strongly anchored in data obtained from ground-based experiments in our laboratory and others. The notion of manipulating diet to minimize bone loss could also have significant social and economic impacts for NASA and for the general public - especially given the increasing trends for diets that are high in animal protein and low in fruits and vegetables. The results of the proposed experiments will lead to development of a dietary countermeasure for bone loss consisting of a balanced diet with no associated risks for side effects that might be present with pharmaceuticals or supplements, no requirement for payload mass, and no additional crew time necessary during flight.

Official Title
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Dietary Intake Can Predict and Protect Against Changes in Bone Metabolism During Spaceflight and Recovery

Conditions
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Bone Resorption

Intervention / Treatment
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* Other: Preflight
* Other: In-flight


Participation Criteria
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Eligibility Criteria
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Inclusion Criteria: Astronauts flying on long-duration (3-6 months) spaceflights Exclusion Criteria: Non-astronauts
Sexes Eligible for Study
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All

Accepts Healthy Volunteers
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Accepts Healthy Volunteers

Study Plan
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How is the study designed?
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Design Details

Primary Purpose: Prevention
Allocation: Randomized
Intervention Model: Crossover Assignment
Masking: None (Open Label)


Arms and Interventions

| Participant Group/Arm | Intervention/Treatment |
| --- | --- |
| Experimental: Low Apro/K Diet<br>Subjects consume a prescribed diet for 4 days with a low ratio of animal protein to potassium (0.3-0.6 g/mEq). | Other: Preflight<br>* 4-d controlled diet sessions will occur twice before flight.<br>Other: In-flight<br>* 4-d controlled diet sessions will take place on flight days 15, 60, 120, and 180. Flight day 30 will only be monitored intakes (subject consume nominal intake)<br>|
| Experimental: High Apro/K Diet<br>Subjects consume a prescribed diet that has a high ratio of animal protein to potassium (1.0-1.3 g/mEq) for 4 days. | Other: Preflight<br>* 4-d controlled diet sessions will occur twice before flight.<br>Other: In-flight<br>* 4-d controlled diet sessions will take place on flight days 15, 60, 120, and 180. Flight day 30 will only be monitored intakes (subject consume nominal intake)<br>|

What is the study measuring?
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Primary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| Change in urinary n-telopeptide after 15 days of space flight compared to preflight | 24-h NTX will be used as an indicator of bone resorption | 15 days | 
| Change in urinary n-telopeptide after 30 days of space flight compared to preflight |  | 30 days | 
| Change in urinary n-telopeptide after 60 days of space flight compared to preflight |  | 60 days | 
| Change in urinary n-telopeptide after 120 days of space flight compared to preflight |  | 120 days | 
| Change in urinary n-telopeptide after 180 days of space flight compared to preflight |  | 180 days | 
| Change in urinary calcium after 15 days of space flight compared to preflight |  | 15 days | 
| Change in urinary calcium after 60 days of space flight compared to preflight |  | 60 days | 
| Change in urinary calcium after 120 days of space flight compared to preflight |  | 120 days | 
| Change in urinary calcium after 180 days of space flight compared to preflight |  | 180 days | 

Secondary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| Change in urinary calcium after 30 days of space flight compared to preflight | 24-h urinary calcium | 30 days | 

 Terms related to the study
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Keywords Provided by Centre Hospitalier Valida
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Bone resorption, Diet