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Clinical Nutrition

This guide provides an overview of resources and search strategies for clinical nutrition research.

The Basics

Using AND, OR, NOT

Boolean logic is a building block of many computer applications and is an important concept in database searching. Using the correct Boolean operator can make all the difference in a successful search.


There are three basic Boolean search commands: AND, OR, and NOT.

  • AND finds all of the search terms. For example, searching on (dengue AND malaria AND zika) returns only results that contain all three search terms. Using AND decreases the number of results.

  • OR finds one term or the other. Searching on (dengue OR malaria OR zika) returns all items that contain any of the three search terms. Using OR increases the number of results.
  • NOT eliminates items that contain the specified term. Searching on (malaria NOT zika) returns items that are about malaria, but will specifically NOT return items that contain the word zika. This is a way to fine-tune results. NOT should only be used in specific circumstances, not as a way to decrease the number of returned results.

Using Boolean Search with Exact Phrases

If you're searching for a phrase rather than just a single word, you can group the words together with quotation marks. Searching on "dengue fever" will return only items with that exact phrase.  

When to use parentheses?

It's a lot like basic math. (2 × 4) + 1 = 9  but 2 × (4 + 1) = 10.

Think of your search in concepts, then put those concepts inside parentheses. Different databases have different rules about combining searches. To make sure you get the search you want, use parentheses - every database follows those rules.For example:

dengue OR malaria AND zika, without parentheses, can be interpreted as:

  • (dengue OR malaria) AND zika = articles about dengue or malaria, that also discuss zika. Every item returned would mention zika and either dengue or malaria. As the zika virus has only recently been a serious issue, this would limit the number of results.
  • dengue OR (malaria AND zika) = every article about dengue, or those that discuss both zika and malaria. Since dengue fever has been a concern for over 250 years, this search would yield different results. Every item about dengue would be returned, as would those that discuss both of the other two.

Translate a PubMed Search into Other Databases

A systematic review should not be written using results from just one database. This page will walk you through translating a PubMed search into various other databases.   

First finalize your search strategy in PubMed. Consult a librarian or use our PubMed guide if you need assistance with this.
-    Use MeSH terms
-    Using [tiab] is usually a good idea 
-    Use quotation marks to keep phrases together
-    Using an asterisk allows for truncation (educat* will return articles that contain educate, educated, education, etc.)

This page will use an ongoing example of a search created to find articles about distal clavicle excisions. The PubMed search string:

((distal[tiab] OR lateral[tiab]) 
AND ("Clavicle"[Mesh] OR clavic*[tiab]) 
AND (excision[tiab] OR resection[tiab] OR "Mumford procedure"[tiab]))
NOT (children OR pediatrics)

Once you have a completed, finalized search strategy in PubMed, it is HIGHLY RECOMMENDED that you paste that search string into a Word document, along with a note about how many results were returned and the date you ran it. This will allow you to re-run the search, and is necessary information for when you write your paper. 

After the PubMed search is finalized: Create a generic search string. Quotation marks and asterisks can be left in. Eliminate all MeSH terms and the tag [tiab]. The generic search string:

((distal OR lateral) 
AND (clavic*) 
AND (excision OR resection OR "Mumford procedure"))
NOT (children OR pediatrics)

You will then add whatever formatting is necessary for the databases you choose to search in. The main goal of translating a search strategy is to make sure that the string remains as consistent as possible across databases.

Which databases should I search?

Which databases you choose to search depends on a multitude of factors, including your research topic, if you're conducting a literature review following a certain set of guidelines, or any requirements of a journal you may plan on submitting to. While there are no official rules for conducting literature searches, it is generally considered good practice to search at least three databases. Additionally, many publications expect literature reviews to include at least one database that indexes MEDLINE (i.e., indexes MeSH terms). Ultimately, the decision regarding which databases are most appropriate for your research topic is up to you.

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