How We Grade Supplement Evidence (A–U)

“Studies show…” is doing a lot of heavy lifting on most supplement pages. But a test-tube experiment and a large human trial are not the same evidence: and a study on an ingredient is not proof that a product containing it works. So every claim we make carries an explicit evidence grade. Here’s the scale, and why it matters.

Why a grading system

Two honesty problems plague supplement reviews: treating weak evidence as strong, and treating ingredient research as product proof. A visible A–U grade forces us, and lets you, to separate what an ingredient can do in general from what this specific product has been shown to do. It’s the same principle behind medical evidence hierarchies, adapted for supplements.

The A–U scale

• Grade A: Finished-formula evidence. An independent human trial tested the exact product, at its actual dose. Strongest. Rare in this industry.
• Grade B: Matching ingredient & dose. Human research on the same ingredient form at a comparable dose to what the product discloses. Solid, when the dose is visible.
• Grade C: Ingredient research, uncertain applicability. The ingredient has human research, but the product’s form, dose, or combination makes it unclear whether that research applies. Most proprietary-blend products live here.
• Grade D: Mechanistic, cell, or animal only. A plausible mechanism, not proof of a result in people.
• Grade U: Unverifiable. We couldn’t confirm the claim from credible sources.

How grades map to the 5-Point Filter

Grades feed directly into our 5-Point Quality Filter. A product can only earn a full Recommended when its key actives reach Grade A or B: which requires disclosed, clinically-relevant doses. When the doses are hidden in a proprietary blend, the actives can’t rise above Grade C for that product, so the dosing check can’t pass and the product gets a Conditional verdict, not a recommendation.

Why most supplements are Grade C

It isn’t cynicism, it’s structure. Most direct-response supplements combine several ingredients in a proprietary blend and have never funded an independent trial of the finished formula. That caps them at Grade C by definition. You can see exactly how this plays out in our Nagano Lean Body Tonic review and Java Burn review, both are Grade C at the product level, and both are Conditional. Products that do disclose full, studied doses can reach Grade B and a genuine recommendation, those are the ones we highlight as top picks.

The bottom line

A grade is a promise about certainty, not a verdict on an ingredient. When you see Grade C on our pages, read it as: “there’s real research on this ingredient, but we can’t confirm it applies to this product as sold.” That honesty is the whole point: and it’s why you can trust the reviews that do say “recommended.”

Educational content only, not medical advice.

References

• Google Search, Write high-quality product reviews, developers.google.com
• NIH Office of Dietary Supplements: ods.od.nih.gov
• PubMed: pubmed.ncbi.nlm.nih.gov