Table 6Criteria for risk of bias assessment

CriteriaExperimental Controlled Trials (RCT and non-RCT)Observational Controlled StudiesUncontrolled Experimental Studies
Selection Bias
Appropriateness of participant selection*XX
Randomization sequence generationX
Allocation concealmentX
Control for important baseline/prognostic factors: restriction, similarity of groups at baseline, matching, and/or adjustment in the analysisXX
Performance Bias
Purity/standardization of dietary supplement§XXX
Blinding of subjects and providers to treatment allocationX
Attrition Bias
Completeness of outcome data (attrition and exclusions) with focus on differential loss to followup or overall high loss to followup and potential for associated confoundingXXX
Detection Bias
Blinding of outcome assessors to treatment or exposure status in experimental or cohort studies or blinding of exposure assessors to case/control status in case-control studies.XXX
Extent to which valid outcomes were describedXXX
Financial conflict of interestXXX
Criteria for assessment of harms (from the McHarm checklist130): prespecified and valid definition of harms, mode of harms collection (e.g., active or passive, standard tool)XXX



Appropriateness of participant selection included whether participants from each arm were from the same or different populations, the use of adequate definitions and measurements of exposed/nonexposed or case/control status and demonstration that outcomes were not present at beginning of prospective studies.

For RCTs only.

Important baseline/prognostic factors evaluated: age, gender, race, baseline diet/nutrient exposures for dietary substance of interest, smoking, concomitant medications/supplements, and health status, including comorbidities and LDL-C and blood pressure if these measures were not included as study outcomes.


Description of the source, methods of extraction, and constituents of the dietary supplement (e.g., quantification or quality assurance/standardization of dose/purity, stability and length of storage).

Definition and methods used to assess outcome including timing, and comparability of assessment across study arms.

Abbreviation: RCT = randomized controlled trial.

From: Methods

Cover of Dietary Supplements in Adults Taking Cardiovascular Drugs
Dietary Supplements in Adults Taking Cardiovascular Drugs [Internet].
Comparative Effectiveness Reviews, No. 51.
Seely D, Kanji S, Yazdi F, et al.

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