An umbrella review (review of reviews) on dietary interventions for cardiovascular disease is a fantastic and much-needed undertaking! It will provide a high-level synthesis of existing evidence.

Here's a comprehensive guide to help you search for existing systematic reviews and meta-analyses on your topic:

1. Deconstruct Your Research Question & Identify Key Concepts

Before you start searching, break down your topic into its core components. This will help you identify appropriate keywords and controlled vocabulary terms.

Core Concepts:

• Study Design: Systematic Review OR Meta-analysis (crucial for an umbrella review)


• Intervention: Dietary Interventions (e.g., specific diets, food groups, nutrients, supplements)


• Outcome/Population: Cardiovascular Disease (CVD) or its risk factors/precursors

2. Identify Relevant Databases

You'll need to search multiple databases to ensure comprehensive coverage.

Primary Databases (Essential):

• PubMed / MEDLINE: Excellent for biomedical literature, uses MeSH (Medical Subject Headings).


• Embase: Broader coverage than PubMed, especially for European literature, pharmaceuticals, and conference abstracts. Uses Emtree.


• Cochrane Library: Specifically focuses on systematic reviews of healthcare interventions. Crucial for SRs/MAs.


• Cochrane Database of Systematic Reviews (CDSR): Contains full Cochrane Reviews.


• CENTRAL (Cochrane Central Register of Controlled Trials): While primarily for RCTs, it can sometimes point to included studies within reviews, or review protocols.


• Web of Science (Core Collection): Interdisciplinary, good for citation tracking and finding highly cited reviews.


• Scopus: Similar to Web of Science, very broad, good for citation tracking.

• Google Scholar: Useful for identifying reviews not indexed in traditional databases, "grey literature," or reviews from less conventional publishers. Be prepared for a lot of noise.


• PROSPERO (International Prospective Register of Systematic Reviews): Crucial for finding registered protocols of systematic reviews. This helps identify ongoing reviews and avoid duplication. While it won't give you published reviews, it's good to check for reviews that will be published soon.

3. Develop Your Keyword Strategy

For each core concept, brainstorm a wide range of keywords, including synonyms, broader terms, narrower terms, and controlled vocabulary (MeSH for PubMed, Emtree for Embase).

Concept 1: Study Design (Systematic Review / Meta-analysis)

This is the most critical filter for an umbrella review.

• Free-text keywords:


• "systematic review" (truncation covers "review", "reviews", "reviewer")


• "meta-analys*" (covers "analysis", "analyses")


• "review of reviews"


• "overview of reviews"


• "umbrella review" (might find other umbrella reviews, good for cross-referencing)


• "evidence synthesis" (broader, might capture some but less precise)


• Controlled Vocabulary (e.g., MeSH in PubMed):


• "Systematic Review" [Publication Type]


• "Meta-Analysis" [Publication Type]

Concept 2: Dietary Interventions

This needs to be broad initially to capture all relevant types, then you can refine.

• General terms:


• "diet*"


• "nutrition*"


• "food*"


• "eating"


• "meal*"


• "dietary intervention*"


• "nutritional intervention*"


• Specific Dietary Patterns/Diets:


• "Mediterranean diet"


• "DASH diet"


• "vegan diet"


• "vegetarian diet"


• "plant-based diet"


• "low carbohydrate diet" OR "low carb diet" OR "ketogenic diet"


• "low fat diet" OR "low-fat diet"


• "high fat diet" OR "high-fat diet"


• "paleo diet" OR "paleolithic diet"


• "gluten-free diet"


• "fasting" OR "intermittent fasting"


• Food Groups/Components:


• "fruits and vegetables" OR "fruit and vegetable*"


• "whole grains"


• "legumes" OR "beans" OR "lentils"


• "nuts" OR "seeds"


• "fish" OR "seafood"


• "red meat" OR "processed meat"


• "dairy" OR "milk" OR "cheese" OR "yogurt"


• "sugar" OR "sugary drink*"


• "salt" OR "sodium"


• Nutrients/Supplements:


• "omega-3 fatty acid" OR "fish oil" OR "EPA" OR "DHA"


• "fiber" OR "fibre"


• "protein*"


• "carbohydrate*"


• "vitamin*" (e.g., "vitamin D", "vitamin B")


• "mineral*" (e.g., "magnesium", "potassium", "calcium")


• "antioxidant*"


• "polyphenol" OR "flavonoid"


• "probiotic" OR "prebiotic"


• "dietary supplement" OR "nutritional supplement"


• "herbal supplement*"


• Controlled Vocabulary (e.g., MeSH):


• "Diet*" [MeSH]


• "Nutrition*" [MeSH]


• "Diet Therapy" [MeSH]


• "Food" [MeSH]


• "Nutrients" [MeSH]


• "Dietary Supplements" [MeSH]


• Specific diet terms like "Diet, Mediterranean" [MeSH], "Diet, DASH" [MeSH], "Vegetarian Diet" [MeSH], "Vegan Diet" [MeSH].


• Specific nutrient terms like "Fatty Acids, Omega-3" [MeSH], "Vitamins" [MeSH].

Concept 3: Cardiovascular Disease (CVD)

• General terms:


• "cardiovascular disease*"


• "heart disease*"


• "cardiac disease*"


• "vascular disease*"


• "atherosclerosis"


• Specific CVDs/Conditions:


• "coronary artery disease" OR "CAD"


• "ischemic heart disease"


• "myocardial infarction" OR "heart attack"


• "stroke" OR "cerebrovascular disease*"


• "heart failure"


• "atrial fibrillation"


• "peripheral artery disease" OR "PAD"


• CVD Risk Factors (if your scope includes prevention via risk factor modification):


• "hypertension" OR "high blood pressure"


• "dyslipidemia" OR "hyperlipidemia" OR "cholesterol" OR "triglycerides"


• "diabetes mellitus" OR "type 2 diabetes"


• "metabolic syndrome"


• "obesity" OR "overweight"


• "inflammation" (if linked to CVD)


• Controlled Vocabulary (e.g., MeSH):


• "Cardiovascular Diseases" [MeSH]


• "Heart Diseases" [MeSH]


• "Coronary Artery Disease" [MeSH]


• "Myocardial Infarction" [MeSH]


• "Stroke" [MeSH]


• "Cerebrovascular Disorders" [MeSH]


• "Hypertension" [MeSH]


• "Dyslipidemias" [MeSH]


• "Diabetes Mellitus" [MeSH]

4. Construct Your Search Strings (Examples)

Combine your keywords using Boolean operators (AND, OR) and phrase searching (""). Remember that specific syntax varies slightly between databases.

General Structure:

(Concept 1: Study Design) AND (Concept 2: Dietary Interventions) AND (Concept 3: Cardiovascular Disease)

Example for PubMed/MEDLINE:

(Note: Always combine MeSH terms with free-text terms for maximum sensitivity)

(
  ("systematic review"[Publication Type] OR "meta-analysis"[Publication Type])
  OR (systematic review* [tiab] OR meta-analys* [tiab] OR "overview of reviews" [tiab])
)
AND
(
  ("Diet"[MeSH] OR "Nutrition"[MeSH] OR "Dietary Supplements"[MeSH] OR "Diet Therapy"[MeSH] OR "Food"[MeSH] OR "Nutrients"[MeSH] OR "Diet, Mediterranean"[MeSH] OR "Diet, DASH"[MeSH] OR "Vegetarian Diet"[MeSH] OR "Vegan Diet"[MeSH] OR "Fatty Acids, Omega-3"[MeSH] OR "Vitamins"[MeSH])
  OR (diet* [tiab] OR nutritio* [tiab] OR food* [tiab] OR "Mediterranean diet" [tiab] OR "DASH diet" [tiab] OR vegan [tiab] OR vegetarian [tiab] OR "plant-based" [tiab] OR "low carb" [tiab] OR "ketogenic diet" [tiab] OR "low fat" [tiab] OR "high fat" [tiab] OR "paleo diet" [tiab] OR "intermittent fasting" [tiab] OR "whole grains" [tiab] OR legumes [tiab] OR nuts [tiab] OR fish [tiab] OR "red meat" [tiab] OR dairy [tiab] OR sugar [tiab] OR salt [tiab] OR sodium [tiab] OR omega-3 [tiab] OR fiber [tiab] OR protein [tiab] OR carbohydrate [tiab] OR vitamin* [tiab] OR mineral* [tiab] OR antioxidant* [tiab] OR polyphenol* [tiab] OR probiotic* [tiab] OR supplement* [tiab])
)
AND
(
  ("Cardiovascular Diseases"[MeSH] OR "Heart Diseases"[MeSH] OR "Coronary Artery Disease"[MeSH] OR "Myocardial Infarction"[MeSH] OR "Stroke"[MeSH] OR "Cerebrovascular Disorders"[MeSH] OR "Hypertension"[MeSH] OR "Dyslipidemias"[MeSH] OR "Diabetes Mellitus"[MeSH])
  OR (cardiovascular disease* [tiab] OR heart disease* [tiab] OR cardiac disease* [tiab] OR vascular disease* [tiab] OR atherosclerosis [tiab] OR "coronary artery disease" [tiab] OR "ischemic heart disease" [tiab] OR "myocardial infarction" [tiab] OR stroke [tiab] OR "heart failure" [tiab] OR hypertension [tiab] OR dyslipidemia [tiab] OR diabetes [tiab] OR "metabolic syndrome" [tiab] OR obesity [tiab])
)

Example for Cochrane Library (specifically CDSR):

The Cochrane Library is already focused on systematic reviews, so you'd primarily focus on the intervention and outcome.

(diet* OR nutritio* OR food* OR "Mediterranean diet" OR "DASH diet" OR vegan OR vegetarian OR "plant-based" OR "low carb" OR "ketogenic diet" OR "omega-3" OR "whole grains" OR "fruits and vegetables" OR salt OR sodium OR sugar OR fiber OR protein OR supplement*)
AND
(cardiovascular disease* OR heart disease* OR stroke OR hypertension OR dyslipidemia OR diabetes)

5. Practical Search Strategy Steps

• Start Broad, Then Refine: Begin with a comprehensive set of keywords. It's better to capture too much initially and filter later than to miss relevant reviews.


• Translate for Each Database: The exact syntax (e.g., proximity operators like NEAR, field codes like [tiab]) will differ for each database. Consult their help guides.


• Use Filters/Limits:


• Publication Type: Most databases allow you to filter by "Systematic Review" or "Meta-Analysis." Use this in addition to your keyword strategy for robustness.


• Language: Typically "English" for most umbrella reviews, but be aware of this limitation.


• Date: Consider if you want to limit to recent reviews (e.g., last 10 years), or include all reviews. For an umbrella review, including all relevant SRs/MAs, regardless of publication date, is often preferred, but you might later choose to analyze by publication date.


• Run Pilot Searches: Test your search strings in one or two databases to see the volume of results and the relevance. Adjust your keywords if you're getting too many irrelevant hits or missing obvious ones.


• Save Your Searches: Most databases allow you to save your search strategy and alerts for new publications. This is crucial for transparency and reproducibility.


• Export Results: Export all your search results (including full citation details and abstracts) into a reference management software (e.g., EndNote, Zotero, Mendeley).


• Deduplicate: Remove duplicate records across databases using your reference management software.


• Screening:


• Title/Abstract Screening: Two independent reviewers should screen titles and abstracts against your pre-defined inclusion and exclusion criteria.


• Full-Text Screening: Retrieve the full text of potentially relevant reviews and have two independent reviewers assess them against your criteria.


• Citation Chasing / Snowballing:


• Backward Citation Chasing: Examine the reference lists of all included systematic reviews to identify any other relevant SRs/MAs that your initial search might have missed.


• Forward Citation Chasing: Use tools like Web of Science or Scopus to see which newer articles have cited your included systematic reviews. This can uncover more recent SRs/MAs on the same topic.


• Document Everything: Meticulously record every step of your search strategy, including database names, search terms, filters applied, dates of search, and number of results. This is essential for the PRISMA flow diagram and the methods section of your umbrella review.


• Register Your Protocol: Register your umbrella review protocol in PROSPERO. This enhances transparency and reduces the risk of duplication.

By following these steps, you'll be well-equipped to conduct a thorough and systematic search for existing systematic reviews and meta-analyses on dietary interventions for cardiovascular disease. Good luck!