Research Library & Evidence Methodology

How We Grade Evidence

Our Evidence Grading System

Not all research is equal. HealthBase applies a structured 4-level evidence grading system to every claim, based on study quality, sample size, replication, and consistency of findings. We follow frameworks used by Cochrane Reviews, the GRADE system, and NHS Evidence Standards.

Strong (5/5)

Strong Evidence

Multiple large, well-designed RCTs with consistent findings across independent research groups. Replicated in systematic reviews or meta-analyses with low heterogeneity. Effect sizes are clinically meaningful and statistically robust.

Examples on HealthBase: Vitamin D & Immunity, Omega-3 & Triglycerides, DASH Diet & Blood Pressure, Exercise & Mortality, Iron Deficiency & Fatigue

Moderate (3/5)

Moderate Evidence

Evidence from RCTs or systematic reviews with some limitations — smaller sample sizes, variable study quality, or inconsistent findings across trials. The direction of effect is generally consistent but magnitude or applicability may vary.

Examples on HealthBase: Magnesium & Sleep, Ashwagandha & Cortisol, Creatine & Cognition, Probiotics & Mood, IBS & Low-FODMAP

Limited (2/5)

Limited Evidence

Preliminary findings from small trials, mechanistic studies, or observational data without RCT confirmation. Direction may be promising but replication is lacking. Claims are presented cautiously with explicit uncertainty acknowledged.

Applies to: Emerging supplement research, novel dietary interventions, early-phase clinical investigations not yet replicated

Emerging (1/5)

Emerging / Preliminary

Animal studies, in-vitro research, case reports, or single pilot studies without replication. Mechanistically plausible but lacking human clinical evidence. Included for completeness with clear labelling that findings should not guide clinical decisions.

Applies to: Early gut-brain axis research, novel biomarker studies, first-in-human trials

Study Type Hierarchy

How We Rank Study Types

Different study designs produce different levels of certainty. We weight evidence according to this hierarchy when grading each topic.

Tier 1 — Highest

Systematic Reviews & Meta-Analyses

Pool data from multiple RCTs to produce the most reliable overall estimate of effect size. Cochrane Reviews are the gold standard.

Tier 2

Randomized Controlled Trials (RCTs)

Participants randomly assigned to treatment or placebo. Double-blind design eliminates most bias. The backbone of supplement and intervention evidence.

Tier 3

Cohort & Prospective Studies

Follow large populations over time to observe associations. Cannot prove causation but essential for long-term and rare outcome research.

Tier 4

Cross-Sectional & Case-Control

Snapshot studies examining associations at a point in time. Useful for generating hypotheses but prone to confounding.

Tier 5

Mechanistic & Animal Studies

In-vitro or animal research explaining biological mechanisms. Provide rationale for human trials but cannot be extrapolated directly to humans.

Tier 6 — Lowest

Expert Opinion & Case Reports

Clinical experience or individual cases. Valuable for generating hypotheses and rare conditions but the weakest form of evidence for efficacy claims.

Editorial Process

How Articles Are Written & Reviewed

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1. Literature Search

PubMed, Cochrane Library, and Google Scholar searched for all relevant peer-reviewed studies on each topic.

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2. Evidence Grading

Each study assessed for design quality, sample size, blinding, conflict of interest, and replication status.

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3. Neutral Summarization

Findings presented neutrally without commercial bias. Conflicting evidence is disclosed. Effect sizes reported, not just significance.

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4. Regular Updates

Articles reviewed when significant new evidence emerges. Last-updated date displayed on every page.

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Medical Disclaimer

All content on HealthBase is for informational purposes only and is not intended as medical advice, diagnosis, or treatment. Evidence grades reflect the current state of published research and may change as new studies emerge. Always consult a qualified healthcare professional before making health decisions.

Our Evidence Grading System

How We Rank Study Types

How Articles Are Written & Reviewed

All Studies Cited on HealthBase