STROBE-nut (STROBE Extension for Nutritional Epidemiology)

What it is

— STROBE-nut (Strengthening the Reporting of Observational Studies in Epidemiology — Nutritional Epidemiology) is a reporting-guideline extension that supplements the parent STROBE Statement with 24 nutrition-specific items (extensions and elaborations of STROBE's core 22-item checklist) for observational studies whose exposures are dietary intake, foods, nutrients, supplements, dietary patterns, or nutritional status. It was published by Lachat et al. in PLOS Medicine in 2016 and is hosted and maintained as a STROBE/EQUATOR extension within the EQUATOR Network. Its purpose is transparency, not validity scoring: it forces authors to make explicit how diet was measured (the assessment instrument and its validation), how foods/nutrients were defined and quantified (food composition tables, brand/processing detail, supplement capture), how total energy intake was handled in the analysis (the energy-adjustment model), and how missing or implausible intake data were treated — the elements that make nutritional-epidemiology results reproducible and comparable across studies but that generic STROBE does not name. STROBE-nut is a companion checklist: it is used alongside STROBE, not instead of it.

When to use

— Apply STROBE-nut when reporting a completed observational study (cohort, case-control, or cross-sectional, including secondary analyses of existing data) in which a primary exposure, mediator, or key covariate is dietary or nutritional. Typical settings: a peer-reviewed nutritional-epidemiology manuscript; the evidence base behind a dietary-guideline review; a real-world cohort linking dietary assessment to claims/EHR/registry outcomes; or a nutrition sub-study within a larger pharmacoepidemiology or HTA evidence package. Decision rule for choosing the right family member: use the core STROBE checklist for any observational study, and add STROBE-nut when nutrition is central; use RECORD (or RECORD-PE for pharmacoepidemiology) when the study is built on routinely-collected health data such as claims/EHR — and if a routinely-collected-data study also has a nutritional exposure, RECORD and STROBE-nut are complementary, addressing the data-source and the diet-measurement dimensions respectively. STROBE-nut governs reporting of a primary study; it is not a protocol checklist (use SPIRIT/HARPER/ENCePP for those) and not a systematic-review checklist (use PRISMA).

What it requires

— Layered on STROBE's title/abstract, introduction, methods, results, and discussion structure, the nutrition-specific items demand: (1) Exposure/dietary-assessment transparency — the named assessment method (FFQ, multiple 24-hour recalls, food records, biomarkers), the number and timing of measurements, and reference to its validation/reproducibility in the study population, with the recognized measurement-error structure of self-reported intake stated rather than ignored. (2) Food/nutrient definition and quantification — the food-composition database and version used, how recipes/mixed dishes/brands/fortification were handled, supplement and fortificant capture, and the units reported. (3) Energy and the analytic model for intake — explicit statement of whether and how total energy intake was adjusted for (standard, residual, energy-partition, or multivariable models), since this choice changes the estimand and the interpretation of any nutrient effect. (4) Data fitness and plausibility — handling of implausible energy intakes, under/over-reporting, and the treatment of missing dietary data. (5) Confounding and effect modification specific to diet (e.g., the entire dietary context, physical activity, total energy). Read for real-world data, these map onto familiar RWE obligations: design transparency, data-fitness-for-use, exposure/algorithm definition and validation, time-zero alignment for incident dietary exposure or follow-up, attrition/missing-data accounting, and pre-specified sensitivity analyses (e.g., excluding implausible reporters).

When NOT to use — limitations and common misapplications

— STROBE-nut is a reporting checklist, not a risk-of-bias instrument and not a quality score. Concrete failure modes: (1) Mistaking it for an appraisal tool — a STROBE-nut-complete paper can still be badly confounded or measurement-error-ridden; to appraise the study use a risk-of-bias/quality tool (e.g., the relevant JBI checklist, NOS, or for RWE-on-routine-data, ROBINS-I), not the reporting checklist. (2) Reporting ≠ causal — completing the checklist makes the methods transparent; it does not make an observational diet–outcome association causal or unconfounded. (3) Wrong extension for the design — using core STROBE alone for a nutrition-central study (omitting the diet-measurement items that determine reproducibility), or using STROBE-nut where the dominant methodological issue is the routinely-collected data source and RECORD is what is actually required. (4) Wrong study object — applying STROBE-nut to a trial (use CONSORT) or to a systematic review/meta-analysis (use PRISMA); STROBE-nut is for primary observational studies. (5) Checklist-as-theater — page-number ticking while the FFQ validation, food-composition source, or energy-adjustment model are left vague defeats the purpose; the value is the substance behind each item, not the completed table.

How it maps to this catalog

— In this repo, STROBE-nut's substantive requirements are implemented by concepts a methodologist can build and report against: - The diet-exposure definition and its validity (assessment-instrument and food/nutrient items) are implemented by algorithm-validation and, where intake is operationalized from coded data, diagnosis-phenotype-algorithm-1ip-2op-time-window-rwe and outcome-algorithm-construction-rwe. - Data-fitness-for-use (the right data to measure diet at all) is implemented by fit-for-purpose-data-assessment-rwe and database-feasibility-attrition-funnel-rwe. - Time-zero alignment for incident exposure/follow-up is implemented by time-zero-index-date-alignment-rwe and continuous-enrollment-observable-time-rwe. - Attrition and missing/implausible dietary data are implemented by attrition-and-loss-to-follow-up-rwe, missing-data-pattern-table-rwe, and missing-data-trimming-winsorization-rwe. - Confounding control and the energy-adjustment/estimand decision are implemented by dags-backdoor-criterion-drug-studies, estimands-ate-att-intercurrent-events-rwe, and the sensitivity machinery in selection-bias-sensitivity-analysis-rwe and e-value-sensitivity-analysis (e.g., excluding implausible reporters; residual-confounding bounds). - Descriptive reporting of the sample and exposure distribution is implemented by descriptive-epidemiology-rwe and baseline-characteristics-and-covariate-balance-rwe.

Applied note (claims/EHR/registry RWE)

Dietary exposure is rarely captured cleanly in routinely collected data, so a real-world nutritional study typically links a cohort with validated dietary assessment (FFQ/24-hour recall/registry diet module) to claims/EHR outcomes. STROBE-nut then forces the link to be reported honestly: name the dietary instrument and its validation in this population, state the food-composition source and energy-adjustment model, and — because the outcome side runs on claims-analysis-style routinely-collected data — report it under RECORD alongside STROBE-nut, with outcome phenotypes validated (claims-outcome-algorithm-ppv-sensitivity-rwe), time-zero aligned, and attrition/missingness on both the diet and outcome sides accounted for. STROBE-nut and RECORD are complementary, not interchangeable: one governs the diet measurement, the other the data source.