How to Read Our Evidence
What do "Strong evidence" and "9/10 effectiveness" actually mean? Here's how to interpret what you see on NutriVouch.
Is more studies always better?
Not really. In evidence-based medicine, the type and quality of studies matter much more than raw count. One well-designed meta-analysis with thousands of participants is more valuable than 50 small studies with conflicting results. We weight meta-analyses and systematic reviews much higher than individual trials because they synthesize results across the entire field.
Why do study counts vary so much?
Some substances like Vitamin D have been studied for decades — hundreds of meta-analyses and thousands of trials across many health goals. Newer compounds like NMN or Spermidine have only a handful of meta-analyses because clinical research takes years and funding. A low count doesn't mean a substance doesn't work — it means we simply don't know enough yet.
What are the confidence tiers?
Confidence Tiers
or ≥100 meta-analyses, or ≥400 RCTs
Extensively studied with strong scientific consensus. Conclusions are highly reliable and unlikely to change with new research.
Examples: Vitamin D, Omega-3, Magnesium, Melatonin, Iron, Zinc, Probiotics
or ≥30 meta-analyses, or ≥150 RCTs
Well-researched with mostly consistent findings. Effects are generally established in clinical literature but more research could refine them.
Examples: Ashwagandha, Saffron, Apigenin, Lycopene, Chromium
or at least 1 meta-analysis
Some clinical evidence available, but fewer high-level reviews. Findings show potential but need replication in larger trials.
Examples: Spermidine, Urolithin A, Lion's Mane, Apple Cider Vinegar, Shilajit
and no meta-analyses
Very limited clinical research. Substance may still work, but there isn't enough data to draw reliable conclusions yet.
Examples: King Trumpet (Mushroom) and similar early-research substances
What's the difference between Confidence Level and Effectiveness Score?
These are two separate signals — they answer different questions and you'll see both on every substance card.
Confidence Level (the colored bars) tells you HOW WELL RESEARCHED a substance is overall — how confident science is about it as a whole.
Effectiveness Score (0–10, shown next to each goal) tells you HOW EFFECTIVE the substance is FOR THAT SPECIFIC GOAL according to scientific consensus.
A substance can be "Strong" evidence overall but score 3/10 for a specific goal where the research shows it doesn't help much. Example: Melatonin has Strong confidence (763 studies), but scores 9/10 for Better Sleep and only 3/10 for Anxiety. Same molecule — completely different evidence per goal.
Effectiveness Score scale (per goal)
Gold standard
This substance IS the treatment of choice (e.g. melatonin → sleep, creatine → muscle growth)
Strong
Multiple meta-analyses support clinical use; recommended by evidence-based guidelines
Moderate
Some clinical support; works for some populations or in specific contexts
Weak
Theoretical mechanism or limited evidence; small trials with mixed results
Minimal
Marketed for the goal but evidence is very thin or non-existent
Not applicable
No plausible mechanism or zero evidence
What counts as a 'study' here?
We only include human clinical research from PubMed — the world's largest biomedical database. Animal studies, test-tube experiments, and case reports are excluded from our tier scoring. Each study must pass quality checks: clear methodology, reasonable sample size, and reported results.
Why do study types have different weights?
Not all studies are equal. The scientific community recognizes a hierarchy — meta-analyses sit at the top because they synthesize results across the entire field:
Study Hierarchy
Meta-Analysis
Combines results from many studies — strongest evidence
Systematic Review
Comprehensive analysis of all available research
Randomized Controlled Trial
Participants randomly assigned, reduces bias
Cohort Study
Observes groups over time — useful but observational
Case-Control Study
Compares groups retrospectively
Why isn't [my favorite supplement] rated higher?
Popular doesn't mean proven. Many widely-marketed supplements have weaker evidence than less famous ones. We base scores strictly on published clinical research, not marketing claims, social media trends, or testimonials. Our goal is honesty, not popularity.
The bottom line
When you see Strong evidence (50+ meta-analyses, 200+ RCTs), that's overwhelming scientific consensus. When you see Emerging evidence (a handful of trials), treat the findings as preliminary. And remember: confidence in the substance is one thing — effectiveness for YOUR specific goal is another. Check both numbers. We're here to give you the data — interpret it with appropriate caution.