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Nutritional Sciences and Toxicology: Lit Reviews

a library research guide to nutrition, metabolic biology, and toxicology resources.

what is

A literature review surveys scholarly articles, books and other sources (e.g. dissertations, conference proceedings) relevant to a particular issue, area of research, or theory, providing a description, summary, and critical evaluation of each work. The purpose is to offer an overview of significant literature published on a topic.
A systematic review is a review of literature focused on a research question that identifies, appraises, selects and synthesizes all quality research evidence relevant to that question. Systematic reviews of high-quality randomized controlled trials are crucial to evidence-based medicine.

An understanding of literature or systematic reviews and how to implement them in practice is important for professionals involved in research and health care. Systematic reviews are not limited to medicine and are common in other sciences where data are collected, published in the literature, and an assessment of methodological quality for a precisely defined subject would be helpful.

Steps to do a systematic or literature review

Step 1: Frame questions for a review
The problems addressed by the review should be in clear, structured questions before beginning review work. Once the review questions have been set, modifications to the protocol should be allowed only if alternative ways of defining the populations, interventions, outcomes or study designs become apparent.|

Step 2: Identify relevant work
The search for studies should be extensive. Multiple resources should be searched without language restrictions. The study selection criteria should flow directly from the review questions and be specified a priori. Reasons for inclusion and exclusion should be recorded.

Step 3: Assess the quality of studies
Study quality assessment is relevant to every step of a review. Question formulation (Step 1) and study selection criteria (Step 2) should describe the minimum acceptable level of design.
Selected studies should be subjected to a general critical appraisal and design-based quality checklists (Step 3). These detailed quality assessments will be used for exploring heterogeneity and informing decisions regarding suitability of meta-analysis (Step 4). In addition they help in assessing the strength of inferences and making recommendations for future research (Step 5).

Step 4: Summarize the evidence
Data synthesis consists of tabulation of study characteristics, quality and effects as well as use of statistical methods for exploring differences between studies and combining their effects (meta-analysis). Exploration of heterogeneity and its sources should be planned in advance (Step 3). If an overall meta-analysis cannot be done, subgroup meta-analysis may be feasible.

Step 5: Interpret the findings
Be careful of bias. Exploration for heterogeneity should help determine whether the overall summary can be trusted, and, if not, the effects observed in high-quality studies should be used for generating inferences. Any recommendations should be graded by reference to the strengths and weaknesses of the evidence.

Components

Similar to primary research, development of the literature review has four stages:

  1. Problem formulation—which topic or field is being examined and what are its component issues?
  2. Literature search—finding materials relevant to the subject being explored
  3. Data evaluation—determining which literature makes a significant contribution to the understanding of the topic
  4. Analysis and interpretation—discussing the findings and conclusions of pertinent literature

Literature reviews should include the following elements:

  • An overview of the subject, issue or theory under consideration, along with the objectives of the literature review
  • Division of works under review into categories (e.g. those in support of a particular position, those against, and those offering alternative theses entirely)
  • Explanation of how each work is similar to and how it varies from the others
  • Conclusions as to which are best considered in their argument, are most convincing of their opinions, and make the greatest contribution to the understanding and development of their area of research

In assessing each piece, consider:

  • Provenance—What are the author's credentials? Are the author's arguments supported by evidence (e.g. primary historical material, case studies, narratives, statistics, recent scientific findings)?
  • Objectivity—Is the author's perspective even-handed or prejudicial? Is contrary data considered or is certain pertinent information ignored to prove the author's point?
  • Persuasiveness—Which of the author's theses are most/least convincing?
  • Value—Are the author's arguments and conclusions convincing? Does the work ultimately contribute in any significant way to an understanding of the subject?

Definition and Use/Purpose:
A literature review may be a chapter of a thesis or dissertation, or may be a self-contained review of writings on a subject. In either case, its purpose is to:

  • Place each work in the context of its contribution to the understanding of the subject under review
  • Describe the relationship of each work to the others under consideration
  • Identify new ways to interpret, and shed light on any gaps in, previous research
  • Resolve conflicts amongst seemingly contradictory previous studies
  • Identify areas of prior scholarship to prevent duplication of effort
  • Point the way forward for further research
  • Place one's original work (in the case of theses or dissertations) in the context of existing literature

The literature review itself, however, does not present new primary scholarship.

Ten steps

What is a Literature Review?
A literature review discusses published information in a particular subject area, time period or research.  It can be a simple summary of sources but usually combines a summary and a synthesis of material.

Ten Steps for Writing a Literature Review:
1. Define a topic and audience:
     - must be interesting to you
     - an important aspect of the field
     - a well-defined issue

2. Search and Re-Search the Literature:
     - keep track of databases and search items
     - keep a list of papers and pdfs,
     - use a management system: Refworks, EndNote, Mendeley
     - define criteria for exclusion
     - use reviews

3. Take NOTES while reading

4. Choose the type of review to write:

  • Mini-review: shorter in length, cover a specific time frame, or narrow subject area
  • Full review: longer, deeper coverage includes details.
  • Descriptive: focuses on methodology, findings, interpretation
  • Integrative: attempt to find common ideas and concepts.

5. Keep the review focused, but broad interest. (could discuss other disciplines affected)

6. Be Critical and consistent: 
       A reader should have an idea of
        - The major achievements in the reviewed field.
       - The areas of debate.
       - The outstanding research questions.

7. Find a logical structure.

Try using a mind-map to draw a conceptual scheme of the review.

Image result for mind-map for nutrition literature review

http://www.tonybuzan.com/gallery/mind-maps/

8. Make use of feedback. Can be peer-reviewed or someone reading a draft.

9. Include your own relevant research but be objective.

10. Be Up-to-date, do not forget older studies.

Original by Marco Pautasso. PLOS. July 2013, vol. 9, issue 7.

AVOID these traps:

  • Trying to read everything: try to read the most relevant work instead.
  • Reading not writing: writing is a way of thinking, - write many drafts.
  • Reminder: Review papers can have abstracts and illustrations.
  • Failing to keep bibliographic information: remember that you will be writing a page entitled “References” at some point.
  • Organizing your review chronologically: Organize your paper by ideas.

Questions:  Your Librarian, Susan Koskinen, skoskine@berkeley.edu

Find Literature & Systematic Reviews

Annual Reviews
Annual Reviews critically reviews significant primary research literature. Each article provides a gateway to the essential primary research literature referenced within each topic.

BIOSIS Previews: enter your search, use limit to "Literature Types" and Review (if available).
Coverage: 1926 - present

Cochrane Database of Systematic Reviews: enter your search, limit to review.
Coverage:  date varies | Some full text |

Embase: enter your search, left menu, use limit to "Literature types"  and select reivew / apply.
Embase is a key resource for systematic reviews and researching evidence-based medicine. Coverage: dates vary

PubMed: enter your search, select filter - 'review'. Includes Systematic Reviews search limit, and peer review. (Guide: HTML | PDF).
Covers: 1946 - present

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