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Types and Levels of Evidence for Nutrition/Dietetic Research

Describes different types of evidence and provides strategies for finding specific types of articles for Nutrition students

Searching for Original Research Articles

This page introduces you to various database search strategies for locating original research articles using keywords, subject headings, and filtering techniques.  First, review the chart for applicable keywords, CINAHL subject headings for searching in the CINAHL database, and MESH terms for searching in the PubMed and other medical/nutrition databases.

Then, note specific filters that you can apply in CINAHL and PubMed to find original research articles more quickly.

To access your Nutrition databases from the library homepage, click on the databases link (to the right of the OneSearch search box). Then select the subject dropdown box, Nutrition, and click search. Now, you should see a curated list of databases for Nutrition students.

Search Strategies for General, CINAHL, and PubMed

Run a keyword search (all fields or title/abstract) on your topic plus one of the following:

  • randomized controlled trial or RCT
  • clinical trial
  • cohort study
  • case-control study
  • cross-sectional study
  • intervention study
  • observational study
  • prospective study
  • retrospective study
  • pilot study
  • longitudinal study
  • survey
  • empirical study

These statistical keywords may be useful to try as an "add-on" if applicable to your research needs:

  • ANOVA or analysis of variance
  • t-test or independent samples t-test
  • chi-square test
  • regression analysis (e.g., linear regression, logistic regression, multiple regression)
  • correlation or Pearson correlation
  • confidence interval
  • p-value
  • standard deviation
  • mean difference
  • odds ratio
  • relative risk
  • hazard ratio
  • multivariate analysis
  • descriptive statistics
  • inferential statistics

This is a non-exhaustive list of CINAHL subject headings you may consider searching for when setting up your search strategy:

  • Randomized Controlled Trials
  • Clinical Trials
  • Prospective Studies
  • Case Control Studies
  • Double-Blind studies
  • Single-Blind studies
  • Triple-Blind Studies

This is a non-exhaustive list of MESH terms you may consider searching for when setting up your search strategy:

  • Randomized Controlled Trial [Publication Type]
  • Clinical Trial [Publication Type]
  • Cohort Studies
  • Case-Control Studies
  • Cross-Sectional Studies
  • Observational Study [Publication Type]
  • Prospective Studies
  • Observational Study [Publication Type]
  • Longitudinal Studies
  • Surveys and Questionnaires
  • Nutrition Surveys

CINAHL Database Filters

CINAHL utilizes filters that can help you locate original research articles more efficiently. Try using the following filters. After you run a search, below the last search box, you will see a "Filters" tab. Helpful filters are:

1. Research Article

2. Randomized Controlled Trials

See screenshot:

CINAHL database filters

PubMed Database Filters

PubMed Filters:

PubMed uses filters that may help you find original research articles faster. Try using the following filters located under Article Type:

  • Clinical Trial
  • Randomized Controlled Trial

See screenshot:

Arrows pointing to filter in Article Type section of Filters (Clinical trial and randomized control trial)

Additional Filters

Go to Article Type Filter

  • Clinical Study
  • Clinical Trial 

And many others to explore....

Visit the PubMed User Guide for an exhaustive list of Article Types.

See screenshot of Additional Filters:

Other Article Type limiters in PubMed