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The ratio of animal protein intake to potassium intake is a predictor of bone resorption in space flight analogues and in ambulatory subjectsBACKGROUND: Bone loss is a critical concern for space travelers, and a dietary countermeasure would be of great benefit. Dietary protein and potassium-associated bicarbonate precursors may have opposing effects on the acid-base balance in the body and therefore on bone loss. OBJECTIVE: In 2 studies, we examined the ability of dietary protein and potassium to predict markers of bone metabolism. DESIGN: In the first study, 8 pairs of male identical twins were assigned to 1 of 2 groups: bed rest (sedentary, or SED, group) or bed rest with supine treadmill exercise in a lower-body negative pressure chamber (EX group). In a second study, groups of 4 subjects lived in a closed chamber for 60 or 91 d, and dietary data were collected for two or three 5-d sessions. Urinary calcium, N-telopeptide, and pyridinium cross-links were measured before bed rest; on bed rest days 5-6, 12-13, 19-20, and 26-27; and daily during the chamber studies. Data were analyzed by Pearson's correlation (P < 0.05). RESULTS: The ratio of animal protein intake to potassium intake was significantly correlated with N-telopeptide in the SED group during bed rest weeks 3 and 4 (r = 0.77 and 0.80) and during the 91-d chamber study (r = 0.75). The ratio of animal protein intake to potassium intake was positively correlated with pyridinium cross-links before bed rest in the EX group (r = 0.83), in the EX group during bed rest week 1 (r = 0.84), and in the SED group during bed rest week 2 (r = 0.72) but not during either chamber study. In both studies, these relations were not significant with the ratio of vegetable protein intake to potassium intake. CONCLUSIONS: The ratio of animal protein intake to potassium intake may affect bone in ambulatory and bed-rest subjects. Changing this ratio may help to prevent bone loss on Earth and during space flight.
Document ID
20050150052
Acquisition Source
Legacy CDMS
Document Type
Reprint (Version printed in journal)
Authors
Zwart, Sara R.
(NASA Johnson Space Center Houston, TX United States)
Hargens, Alan R.
Smith, Scott M.
Date Acquired
August 23, 2013
Publication Date
October 1, 2004
Publication Information
Publication: The American journal of clinical nutrition
Volume: 80
Issue: 4
ISSN: 0002-9165
Subject Category
Aerospace Medicine
Funding Number(s)
CONTRACT_GRANT: M01-RR00827
Distribution Limits
Public
Copyright
Other
Keywords
Clinical Trial
Twin Study
Randomized Controlled Trial

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