Document Detail

Meta-analysis of the quantity of calcium excretion associated with the net acid excretion of the modern diet under the acid-ash diet hypothesis.
MedLine Citation:
PMID:  18842807     Owner:  NLM     Status:  MEDLINE    
BACKGROUND: The acid-ash diet hypothesis of osteoporosis suggests that acid from the modern diet causes a demineralization of the skeleton, and mobilized bone calcium is excreted. A systematic approach has not been used to summarize the findings of the numerous studies about the hypothesis. OBJECTIVES: The purpose of this meta-analysis was to estimate the quantity of net acid excretion and calciuria associated with the modern diet, to assess the association between acid excretion and calcium excretion, and to assess the influence of urine preservatives on calcium measurement. DESIGN: We systematically searched for trials of the acid-ash hypothesis and conducted a meta-analysis. RESULTS: Twenty-five of 105 studies met the inclusion criteria. The estimated quantity of net acid excretion from the weighted average of the control diets from 11 studies was 47 mEq/d. The increase in urinary calcium with a change in renal net acid excretion depended on whether the urine was acidic or alkaline (P < 0.001). A significant linear relation was observed between net acid excretion and calcium excretion for both acidic and alkaline urine (P < 0.001). The estimated change in urine calcium associated with a change of 47 mEq of net acid excretion in acidic urine was 1.6 mmol/d (66 mg/d) of calcium. CONCLUSION: Evidence suggests a linear association between changes in calcium excretion in response to experimental changes in net acid excretion. However, this finding is not evidence that the source of the excreted calcium is bone or that this calciuria contributes to the development of osteoporosis.
Tanis R Fenton; Michael Eliasziw; Andrew W Lyon; Suzanne C Tough; David A Hanley
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Publication Detail:
Type:  Journal Article; Meta-Analysis; Research Support, Non-U.S. Gov't    
Journal Detail:
Title:  The American journal of clinical nutrition     Volume:  88     ISSN:  1938-3207     ISO Abbreviation:  Am. J. Clin. Nutr.     Publication Date:  2008 Oct 
Date Detail:
Created Date:  2008-10-09     Completed Date:  2008-11-04     Revised Date:  2009-05-15    
Medline Journal Info:
Nlm Unique ID:  0376027     Medline TA:  Am J Clin Nutr     Country:  United States    
Other Details:
Languages:  eng     Pagination:  1159-66     Citation Subset:  AIM; IM    
Department of Community Health Sciences, University of Calgary, Calgary, AB, Canada.
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MeSH Terms
Acid-Base Imbalance / chemically induced,  metabolism
Biological Markers / urine
Bone Demineralization, Pathologic / etiology,  urine*
Bone Resorption / urine*
Bone and Bones / metabolism
Calcium / metabolism,  urine*
Cross-Sectional Studies
Diet / adverse effects*
Hydrogen-Ion Concentration
Linear Models
Osteoporosis / urine
Reg. No./Substance:
0/Biological Markers; 7440-70-2/Calcium
Comment In:
Am J Clin Nutr. 2009 Mar;89(3):926-7; author reply 927   [PMID:  19158215 ]

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