Cohort studyindependent cross-checkabstract checked★ key study I-FAT-101 in-depth review

More butter linked to higher mortality; plant oils to lower

Butter and Plant-Based Oils Intake and Mortality.

Overview

Zhang Y et al.. JAMA Intern Med 2025 · PMID 40048719 · DOI 10.1001/jamainternmed.2025.0205

Highest v lowest butter HR 1.15; swapping 10 g butter for plant oil linked to 17% lower mortality.

Does the study support the specific claim? No · Methodological quality: moderate

Study explained simply

What did the researchers want to find out?: Compare butter and plant oils with mortality.
How was the study done?: Three cohorts, 33 years.
How many people, animals or samples were studied?: 221,054 adults.
What was actually found?: Butter higher, plant oils lower mortality.
How large was the observed effect?: HR 1.15 v 0.84.
What do the results mean in everyday life?: Using plant oils instead of butter is likely healthier.
What are the study's limitations?: Observational.
What does it say about Elawady's specific claim?: Contradicts 'butter is harmless'.
Do the results apply to Germany and Europe?: US data.
What can explicitly not be concluded from this study?: Cannot prove butter causes death.

Authors: Zhang Y et al.
Journal: JAMA Intern Med
Year: 2025
Identifier: PMID 40048719 DOI 10.1001/jamainternmed.2025.0205
Verification: verified – PubMed efetch 2026-10-26
Retracted: no
Corrections: none
Extent checked: abstract only
Conflicts of interest and funding: NIH grants; one author reports grants from Novo Nordisk Foundation and the International Nut and Dried Fruit Council outside the work.

Are butter and plant-based oil intakes associated with total and cause-specific mortality?

Study design: Cohort study – Three prospective cohorts (NHS, NHSII, HPFS), FFQ every 4 years, up to 33 y follow-up
Population: US health professionals free of cancer, CVD, diabetes, neurodegenerative disease
Country: USA
Period: 1990-2023
Sample size: 221,054; 50,932 deaths
Inclusion and exclusion criteria: Free of major chronic disease at baseline

Exposure / intervention: Butter (table and cooking); plant oils (safflower, soybean, corn, canola, olive)
Comparator: Lowest quartile; substitution models
Endpoints: Total, cancer and CVD mortality
Statistical methods: Multivariable Cox; substitution analysis

Results: Highest v lowest butter: total mortality HR 1.15 (1.08-1.22); highest v lowest plant oils 0.84 (0.79-0.90). Per 5 g/d canola 0.85 (0.78-0.92), soybean 0.94 (0.91-0.96), olive 0.92 (0.91-0.94). Per 10 g/d plant oils: cancer mortality 0.89 (0.85-0.94), CVD mortality 0.94 (0.89-0.99); butter and cancer mortality 1.12 (1.04-1.20). Substituting 10 g/d butter with plant oils: total mortality 0.83 (0.79-0.86).
Absolute risks: not reported in abstract (stats/C-FAT-01_butter_ghee.py)
Authors' conclusion: Higher butter intake was associated with increased mortality, higher plant-based oil intake with lower mortality; substituting butter with plant oils may confer substantial benefits.

Moderate relative associations; consistent across oils; absolute differences not computable from abstract.

The largest recent study of butter itself associates higher butter intake with higher mortality and replacement by plant oils with lower mortality.

I-FAT-03 (near-null butter associations at modest intakes); PURE butter null (I-DRY-106).

US; ghee similar in fatty-acid profile (assumption).

Moderate observational evidence against butter being harmless at higher intakes.

Multidimensional assessment
Multidimensional assessment
Authenticity of the source	verified
Methodological quality	moderate
Risk of bias	some concerns
Precision of results	high
Directness	direct
Reproducibility	partly replicated
Consistency with the overall evidence	mixed
Regional transferability	moderate
Adequacy of the interpretation (by the archive)	not applicable

Ghee-specific data.