Dietary Reference Intakes for Calcium and Vitamin D

BOX 4-1

AHRQ Critical Appraisal and Grading of Evidence

Grading system used by AHRQ-Ottawa:

Basic Jadad score is assessed based on the answer to five questions listed below. Questions that are answered with a “yes” gain 1 point; questions answered with a “no” receive 0 points; the maximum score is 5. A score of 0 to 2 points is considered “low” quality, and a score of 3 to 5 points is considered “high” quality.

Was the study described as random?
Was the randomization scheme described and appropriate?
Was the study described as double-blind?
Was the method of double-blinding appropriate? (Were both the patient and the assessor appropriately blinded?)
Was there a description of dropouts and withdrawals?

Grading system used by AHRQ-Tufts (based on criteria below):

A = highest quality

Studies have the least bias and results are considered valid. These studies adhere mostly to the commonly held concepts of high quality, including the following: a formal study design; clear description of the population, setting, interventions, and comparison groups; appropriate measurement of outcomes; appropriate statistical and analytical methods and reporting; no reporting errors; less than 20 percent dropout; clear reporting of dropouts; and no obvious bias. Studies must provide valid estimation of nutrient exposure from dietary assessments and/or biomarkers with reasonable ranges of measurement errors and justifications for approaches to control for confounding in their design and analyses.

B = medium quality

Studies are susceptible to some bias, but not sufficient to invalidate the results. They do not meet all the criteria in category “A”; they have some deficiencies, but none likely to cause major bias. The study may be missing information, making it difficult to assess limitations and potential problems.

C = low quality

Studies have significant bias that may invalidate the results. These studies have serious errors in design, analysis, or reporting; there are large amounts of missing information or discrepancies in reporting.

SOURCES: Jadad et al., 1996; Cranney et al., 2007; Chung et al., 2009.

Table of Contents

Front Matter R1-R16

Summary 1-14

1 Introduction 15-34

2 Overview of Calcium 35-74

3 Overview of Vitamin D 75-124

4 Review of Potential Indicators of Adequacy and Selection of Indicators: Calcium and Vitamin D 125-344

5 Dietary Reference Intakes for Adequacy: Calcium and Vitamin D 345-402

6 Tolerable Upper Intake Levels: Calcium and Vitamin D 403-456

7 Dietary Intake Assessment 457-478

8 Implications and Special Concerns 479-512

9 Information Gaps and Research Needs 513-522

Appendix A: Acronyms, Abbreviations, and Glossary 523-536

Appendix B: Issues and Interests Identified by Study Sponsors 537-538

Appendix C: Methods and Results from the AHRQ-Ottawa Evidence-Based Report on Effectiveness and Safety of Vitamin D in Relation to Bone Health 539-724

Appendix D: Methods and Results from the AHRQ-Tufts Evidence-Based Report on Vitamin D and Calcium 725-1012

Appendix E: Literature Search Strategy 1013-1018

Appendix F: Evidence Maps 1019-1024

Appendix G: Cases Studies of Vitamin D Toxicity 1025-1034

Appendix H: Estimated Intakes of Calcium and Vitamin D from National Surveys 1035-1044

Appendix I: Proportion of the Population Above and Below 40 nmol/L Serum 25-Hydroxyvitamin D Concentrations and Cumulative Distribution of Serum 25-Hydroxyvitamin D Concentrations: United States and Canada 1045-1058

Appendix J: Workshop Agenda and Open Session Agendas 1059-1064

Appendix K: Biographical Sketches of Committee Members 1065-1074

Index 1075-1102

Summary Tables: Dietary Reference Intakes 1103-1116