Not all research is created equal. Understanding how to evaluate evidence quality is crucial for making informed decisions about supplements. This guide explains our rating system and teaches you to critically evaluate health claims.

The Evidence Pyramid

Meta-Analyses & Systematic Reviews
Randomized Controlled Trials (RCTs)
Cohort Studies
Case-Control Studies
Case Reports & Expert Opinion

Higher levels represent stronger evidence

Our Evidence Rating System

🟢 Strong Evidence

Multiple high-quality RCTs, meta-analyses, or systematic reviews with consistent results. Benefits are well-established with clear dosing guidelines.

Examples: Creatine for strength, Vitamin D for bone health, Omega-3 for triglycerides

🟡 Moderate Evidence

Several RCTs with mostly positive results, or strong observational studies. Benefits are likely but optimal dosing may vary.

Examples: Ashwagandha for stress, Magnesium for sleep, Curcumin for inflammation

🟠 Preliminary Evidence

Limited RCTs, pilot studies, or promising animal/cell studies. More research needed to confirm benefits in humans.

Examples: Lion's Mane for cognition, NMN for longevity, Berberine for glucose

🔴 Insufficient/Anecdotal

Primarily traditional use, case reports, or marketing claims. Little to no clinical evidence in humans.

Examples: Many "proprietary blends," exotic superfoods, miracle cures

Understanding Study Types

Meta-Analysis

A statistical analysis combining results from multiple studies. The gold standard when done well, as it pools data from many trials to reach more reliable conclusions.

Randomized Controlled Trial (RCT)

Participants are randomly assigned to receive either the treatment or a placebo. Double-blind RCTs (where neither participants nor researchers know who gets what) are most reliable.

Observational Studies

Researchers observe outcomes without intervention. Can show correlations but cannot prove causation. Useful for safety monitoring and generating hypotheses.

Red Flags in Research

  • Funded by supplement companies - Not disqualifying, but warrants skepticism
  • Very small sample sizes - Studies with fewer than 30 participants are less reliable
  • Short duration - 2-week trials may miss long-term effects
  • Surrogate markers only - Blood levels improved, but did health outcomes?
  • Cherry-picked outcomes - Did they measure 20 things and report only the 2 that worked?
  • Rodent studies extrapolated to humans - Mice are not little humans

How We Rate Supplements

For each benefit claim on SupplementWiki, we evaluate:

  1. Number of studies - More independent replications = stronger evidence
  2. Study quality - RCTs weighted higher than observational studies
  3. Consistency - Do most studies agree, or are results mixed?
  4. Effect size - Is the benefit meaningful or statistically weak?
  5. Study population - Results in athletes may not apply to sedentary adults

💡 Critical Thinking Tips

  • Be skeptical of "breakthrough" claims - real science advances gradually
  • Check if studies are funded by parties with financial interest
  • Look for replication - one study is interesting, five are compelling
  • Consider the source - peer-reviewed journals vs. company websites
  • Correlation ≠ causation - people who take vitamins may just be healthier overall