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Causal assessment of dietary acid load and bone disease: a systematic review & meta-analysis applying Hill's epidemiologic criteria for causality.

Abstract

BACKGROUND

Modern diets have been suggested to increase systemic acid load and net acid excretion. In response, alkaline diets and products are marketed to avoid or counteract this acid, help the body regulate its pH to prevent and cure disease. The objective of this systematic review was to evaluate causal relationships between dietary acid load and osteoporosis using Hill's criteria.

METHODS

Systematic review and meta-analysis. We systematically searched published literature for randomized intervention trials, prospective cohort studies, and meta-analyses of the acid-ash or acid-base diet hypothesis with bone-related outcomes, in which the diet acid load was altered, or an alkaline diet or alkaline salts were provided, to healthy human adults. Cellular mechanism studies were also systematically examined.

RESULTS

Fifty-five of 238 studies met the inclusion criteria: 22 randomized interventions, 2 meta-analyses, and 11 prospective observational studies of bone health outcomes including: urine calcium excretion, calcium balance or retention, changes of bone mineral density, or fractures, among healthy adults in which acid and/or alkaline intakes were manipulated or observed through foods or supplements; and 19 in vitro cell studies which examined the hypothesized mechanism. Urine calcium excretion rates were consistent with osteoporosis development; however calcium balance studies did not demonstrate loss of whole body calcium with higher net acid excretion. Several weaknesses regarding the acid-ash hypothesis were uncovered: No intervention studies provided direct evidence of osteoporosis progression (fragility fractures, or bone strength as measured using biopsy). The supporting prospective cohort studies were not controlled regarding important osteoporosis risk factors including: weight loss during follow-up, family history of osteoporosis, baseline bone mineral density, and estrogen status. No study revealed a biologic mechanism functioning at physiological pH. Finally, randomized studies did not provide evidence for an adverse role of phosphate, milk, and grain foods in osteoporosis.

CONCLUSIONS

A causal association between dietary acid load and osteoporotic bone disease is not supported by evidence and there is no evidence that an alkaline diet is protective of bone health.

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  • Authors+Show Affiliations

    ,

    Department of Community Health Sciences, University of Calgary, Calgary, AB, Canada. tanisfenton@shaw.ca

    , , ,

    Source

    Nutrition journal 10: 2011 Apr 30 pg 41

    MeSH

    Adult
    Animals
    Bone Resorption
    Calcium
    Causality
    Diet
    Dietary Proteins
    Guidelines as Topic
    Humans
    Models, Animal
    Osteoporosis
    Phosphates
    Potassium
    Randomized Controlled Trials as Topic

    Pub Type(s)

    Journal Article
    Meta-Analysis
    Research Support, Non-U.S. Gov't
    Review
    Systematic Review

    Language

    eng

    PubMed ID

    21529374

    Citation

    Fenton, Tanis R., et al. "Causal Assessment of Dietary Acid Load and Bone Disease: a Systematic Review & Meta-analysis Applying Hill's Epidemiologic Criteria for Causality." Nutrition Journal, vol. 10, 2011, p. 41.
    Fenton TR, Tough SC, Lyon AW, et al. Causal assessment of dietary acid load and bone disease: a systematic review & meta-analysis applying Hill's epidemiologic criteria for causality. Nutr J. 2011;10:41.
    Fenton, T. R., Tough, S. C., Lyon, A. W., Eliasziw, M., & Hanley, D. A. (2011). Causal assessment of dietary acid load and bone disease: a systematic review & meta-analysis applying Hill's epidemiologic criteria for causality. Nutrition Journal, 10, p. 41. doi:10.1186/1475-2891-10-41.
    Fenton TR, et al. Causal Assessment of Dietary Acid Load and Bone Disease: a Systematic Review & Meta-analysis Applying Hill's Epidemiologic Criteria for Causality. Nutr J. 2011 Apr 30;10:41. PubMed PMID: 21529374.
    * Article titles in AMA citation format should be in sentence-case
    TY - JOUR T1 - Causal assessment of dietary acid load and bone disease: a systematic review & meta-analysis applying Hill's epidemiologic criteria for causality. AU - Fenton,Tanis R, AU - Tough,Suzanne C, AU - Lyon,Andrew W, AU - Eliasziw,Misha, AU - Hanley,David A, Y1 - 2011/04/30/ PY - 2010/08/11/received PY - 2011/04/30/accepted PY - 2011/5/3/entrez PY - 2011/5/3/pubmed PY - 2011/9/16/medline SP - 41 EP - 41 JF - Nutrition journal JO - Nutr J VL - 10 N2 - BACKGROUND: Modern diets have been suggested to increase systemic acid load and net acid excretion. In response, alkaline diets and products are marketed to avoid or counteract this acid, help the body regulate its pH to prevent and cure disease. The objective of this systematic review was to evaluate causal relationships between dietary acid load and osteoporosis using Hill's criteria. METHODS: Systematic review and meta-analysis. We systematically searched published literature for randomized intervention trials, prospective cohort studies, and meta-analyses of the acid-ash or acid-base diet hypothesis with bone-related outcomes, in which the diet acid load was altered, or an alkaline diet or alkaline salts were provided, to healthy human adults. Cellular mechanism studies were also systematically examined. RESULTS: Fifty-five of 238 studies met the inclusion criteria: 22 randomized interventions, 2 meta-analyses, and 11 prospective observational studies of bone health outcomes including: urine calcium excretion, calcium balance or retention, changes of bone mineral density, or fractures, among healthy adults in which acid and/or alkaline intakes were manipulated or observed through foods or supplements; and 19 in vitro cell studies which examined the hypothesized mechanism. Urine calcium excretion rates were consistent with osteoporosis development; however calcium balance studies did not demonstrate loss of whole body calcium with higher net acid excretion. Several weaknesses regarding the acid-ash hypothesis were uncovered: No intervention studies provided direct evidence of osteoporosis progression (fragility fractures, or bone strength as measured using biopsy). The supporting prospective cohort studies were not controlled regarding important osteoporosis risk factors including: weight loss during follow-up, family history of osteoporosis, baseline bone mineral density, and estrogen status. No study revealed a biologic mechanism functioning at physiological pH. Finally, randomized studies did not provide evidence for an adverse role of phosphate, milk, and grain foods in osteoporosis. CONCLUSIONS: A causal association between dietary acid load and osteoporotic bone disease is not supported by evidence and there is no evidence that an alkaline diet is protective of bone health. SN - 1475-2891 UR - https://www.unboundmedicine.com/medline/citation/21529374/full_citation L2 - https://nutritionj.biomedcentral.com/articles/10.1186/1475-2891-10-41 DB - PRIME DP - Unbound Medicine ER -