HOME HELP FEEDBACK SUBSCRIPTIONS ARCHIVE SEARCH TABLE OF CONTENTS		QUICK SEARCH:   [advanced] Author: Keyword(s): Year:  Vol:  Page:

This Article Full Text Full Text (PDF) Purchase Article View Shopping Cart Alert me when this article is cited Alert me if a correction is posted Citation Map Services Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via HighWire Citing Articles via Google Scholar Google Scholar Articles by Zwart, S. R Articles by Smith, S. M Search for Related Content PubMed PubMed Citation Articles by Zwart, S. R Articles by Smith, S. M Agricola Articles by Zwart, S. R Articles by Smith, S. M

The ratio of animal protein intake to potassium intake is a predictor of bone resorption in space flight analogues and in ambulatory subjects^1,2,3

¹ From the Human Adaptation and Countermeasures Office, NASA Lyndon B Johnson Space Center, Houston (SRZ and SMS), and the Department of Orthopaedic Surgery, University of California, San Diego, UCSD Medical Center, San Diego (ARH).

Background: 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.

Key Words: Food intake • dietary protein • dietary potassium • bones • collagen cross-links • bone markers • calcium • humans

This article has been cited by other articles:

				S. R. Zwart, J. E. Davis-Street, D. Paddon-Jones, A. A. Ferrando, R. R. Wolfe, and S. M. Smith Amino acid supplementation alters bone metabolism during simulated weightlessness J Appl Physiol, July 1, 2005; 99(1): 134 - 140. [Abstract] [Full Text] [PDF]