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How to read this

The grading scale, the four failure categories, and the one number that explains why this publication exists at all.

The number this whole text is built around

A In the most recent umbrella review of dietary patterns and inflammatory markers, 60 meta-analyses were assessed for certainty under GRADE. Two per cent reached high certainty. Moderate: 52%. Low: 30%. Very low: 15%. Among the 61 narrative syntheses in the same review, high certainty: zero (Reyneke 2026, PMID 40657695, p. 1180).

Methodological quality of the 30 included reviews, assessed with AMSTAR-2: high 30%, moderate 33%, low 27%, critically low 10%.

Read that twice. It does not say the field is worthless. It says that when somebody states a claim from this field at full confidence, there is a 98% chance the underlying evidence does not support that tone. The gap between how firm a claim sounds and how firm it is — that gap is what this publication measures.

The scale

Grades describe the strength of the evidence behind a statement. They say nothing about how large the effect is, how often the claim is repeated, or how plausible the mechanism sounds.

A Several independent syntheses agree; high-to-moderate GRADE certainty.

B One good meta-analysis, or consistent randomised trials; moderate certainty.

C Observational or mechanistic evidence only; low certainty.

D Weak, contradicted, or without controlled human evidence.

Where a source reports its own GRADE assessment, that assessment is used rather than a re-derived one, and the source is named. Where a statement sits between two grades, it is recorded at the lower one.