assay grade

Part 1 of 6 · The gap

2% of the evidence is certain. The other 98% is sold as if it were.

Sixty meta-analyses of diet and inflammatory markers were rated for certainty. Two per cent reached high. That one number is the reason this publication exists.

A 2026 umbrella review gathered 30 systematic reviews of dietary patterns and inflammatory markers and rated the certainty of every one of its 60 meta-analyses under GRADE, the standard system for grading evidence.

Certainty of 60 meta-analyses
  • High2%
  • Moderate52%
  • Low30%
  • Very low15%

Source: Reyneke 2026, PMID 40657695, p. 1180

Two per cent reached high certainty. Among the 61 narrative syntheses in the same review, high certainty was zero.

That does not make the field worthless. It means that when a claim from this field is stated at full confidence, there is a 98% chance the evidence underneath does not support that tone. The distance between how firm a claim sounds and how firm it is — that distance is what this publication measures, claim by claim.

Open the chapter this comes from

Behind the paywall · part 1

The 98% is where the money goes

  • The four ways a popular claim fails
  • What a grade does not tell a reader
  • The verification rule: every figure checked against its primary record
  • Why the wording of a claim changes what a reader should do

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2% of the evidence is certain. The other 98% is sold as if it were. — Assay Grade