O-71 - Serum beta-carotene shows a strong protective mortality association in cohorts (RR 0.69) that randomized trials exclude
A referenced fact resting on no data of the Viewpoint’s own. Discriminating value: even when dietary measurement error is bypassed with a biochemical assay, the cohort association failed to replicate in randomized trials — evidence that the confounding/selection problem, not just measurement error, drives nutritional-cohort associations.
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Why this is evidence
A strong protective cohort mortality association (RR 0.69), measured with an objective biomarker (so not measurement error), is fully excluded by RCTs — a template for a protective observational signal being healthy-user/selection confounding rather than causal. This raises H-7 (the Asian inverse is confounding) and H-50 (artefact) relative to H-22 (a real protective regional effect).