B
Is Serum Gamma Glutamyltransferase a Marker of Oxidative Stress?
Lee DH, Blomhoff R, Jacobs DR • Free Radic Res • 2004
GGT is a marker of oxidative stress, not just liver disease
oxidative stressCardiovascular
Scientific References
The research behind Metabolicum's evidence-based approach
How We Evaluate Evidence
Not all research is equal. We assign confidence grades to each source based on study design, sample size, replication status, and methodology. This helps you understand how confident you can be in each finding.
Grade A
High Confidence
Replicated findings across multiple well-designed studies
Grade B
Good Confidence
Well-designed single studies with strong methodology
Grade C
Moderate Confidence
Observational data with consistent patterns
Grade D
Emerging Evidence
Mechanistic or theoretical - interpret cautiously
Grade E
Clinical Consensus
Practitioner experience without formal trials
Understanding the Reproducibility Crisis
Why are we so careful about evidence grading? Because a significant portion of published research fails to replicate.
| Study | Finding | Grade |
|---|---|---|
| Begley & Ellis, 2012 | Only 21% of landmark cancer studies could be replicated | A |
| Open Science Collaboration, 2015 | Only 36% of psychology studies replicated | A |
| Ioannidis, 2005 | Theoretical framework explaining why most findings are false | A |
This doesn't mean you should distrust all research. It means:
- •Single studies warrant caution — Replication matters
- •Peer review is necessary but not sufficient — Many peer-reviewed findings are later overturned
- •Effect size matters more than p-values — Statistical significance ≠ practical importance
- •Longer studies are generally more reliable — Short-term biomarker changes may not reflect long-term outcomes
We grade evidence honestly so you can calibrate your confidence appropriately.
Research Library
In-depth analysis of foundational studies with translated summaries
Showing studies cited on: GGT Guide
Showing 10 studies
Review Article
A
Gamma-Glutamyltransferase as a Risk Factor for Cardiovascular Disease Mortality
Ruttmann E, Brant LJ, Concin H, et al. • Circulation • 2005
Upper-normal GGT increases cardiovascular mortality by 64% in men
Cardiovascularmortality
A
Gamma Glutamyl Transferase: Comprehensive Review
Whitfield JB • Crit Rev Clin Lab Sci • 2001
Established GGT as a key marker beyond alcohol detection
Liver Healthalcohol
A
Gamma Glutamyl Transferase and Metabolic Syndrome, Cardiovascular Disease, and Mortality Risk
Lee DS, Evans JC, Robins SJ, et al. • Arterioscler Thromb Vasc Biol • 2007
GGT independently predicts metabolic syndrome and CVD risk
Metabolic SyndromeCardiovascular
B
Prognostic Value of Serum Gamma-Glutamyl Transferase After Myocardial Infarction
Emdin M, Passino C, Michelassi C, et al. • Eur Heart J • 2001
Elevated GGT after MI predicts worse cardiac outcomes
Cardiovascular
A
The Value of Gamma-Glutamyltransferase in Cardiovascular Risk Prediction
Wannamethee SG, Lennon L, Shaper AG • Atherosclerosis • 2008
GGT adds predictive value beyond traditional CVD risk factors
Cardiovascularrisk prediction
B
Gamma-Glutamyltransferase: A Predictive Biomarker of Cellular Antioxidant Inadequacy and Disease Risk
Koenig G, Seneff S • Dis Markers • 2015
Framingham: highest GGT quartile HR 1.67 for CVD, HR 2.54 for MetS; Austrian study: GGT >56 U/L men/>36 U/L women = 100% increased mortality risk
Liver HealthCardiovascularInflammation
A
Coffee and Tea Consumption Are Associated with Lower Incidence of Chronic Liver Disease
Ruhl CE, Everhart JE • Gastroenterology • 2005
2+ cups of coffee daily associated with lower GGT and liver disease risk
Liver Healthlifestyle
B
Contribution of Hepatitis B Virus Infection to Liver Cancer Risk
Loomba R, Yang HI, Su J, et al. • Gastroenterology • 2013
HBV infection significantly increases liver cancer risk
Liver Healthcancer
A
Gamma-Glutamyltransferase Is Associated with Incident Vascular Events
Fraser A, Harris R, Sattar N, et al. • Circulation • 2007
GGT predicts vascular events in women independently of traditional risk factors
Cardiovascularvascular
How We Use References
In Calculators
Primary thresholds come from Grade A sources. When Grade A evidence suggests a range rather than a single value, we present the range with context.
In Educational Content
We draw on Grades A-C for educational claims, clearly labeling evidence quality. Grade D and E content is marked as theoretical or practitioner-derived.
In Paradigm Frameworks
- Standard Medical: Grade A (established guidelines)
- Research Consensus: Grade A-B (outcome research)
- Metabolic Optimization: Grade B-E (intervention research + clinical consensus)
Related Pages
Evidence Grades
Grade A: High ConfidenceReplicated findings across multiple studiesGrade B: Good ConfidenceWell-designed single studiesGrade C: Moderate ConfidenceObservational data with consistent patternsGrade D: Emerging EvidenceMechanistic or theoreticalGrade E: Clinical ConsensusPractitioner consensus
Other Pages
This bibliography contains the research supporting Metabolicum's evidence-based approach.
Last comprehensive review: December 2025