Butter and Mortality Risk: Striking Findings From a Study of 200 Thousand People

The Butter Debate Takes a New Turn

The public debate over butter, increasingly used in our kitchens, continues to ask: “Is butter healthy or not?” This study adds a new dimension to the discussion.

Our eating habits directly affect health, and research over the years has improved our understanding of these effects. A new study led by Yu Zhang and colleagues at the Harvard T.H. Chan School of Public Health, involving more than 200 thousand adults and published on 6 March 2025 in JAMA International Medicine , suggests that long-term butter consumption increases all-cause and cancer mortality risk, while plant-based oils may be protective.

Comparison With Previous Research

A 2016 meta-analysis found small or neutral associations between butter and cardiovascular disease, diabetes, and mortality. However, that study compared butter consumption with a Western diet, whereas the Harvard study directly compared butter with plant-based oils, offering a clearer assessment.

These findings agree with earlier research on the adverse health effects of saturated fat. Regularly repeated dietary assessments over many years allowed this study to measure the effects more accurately and clearly. What exactly does it tell us, and which findings stand out?

Study Details

The study analyzed data from 221054 adults in three large United States cohorts: the Nurses' Health Study (NHS), NHS II, and the Health Professionals Follow-up Study (HPFS). Participants initially had no cancer, cardiovascular disease, diabetes, or neurodegenerative disease.

• Dietary Habits: Participants completed food-frequency questionnaires every four years. Butter intake was calculated from amounts added to foods or used in cooking. Plant-based oil intake covered safflower, soybean, corn, canola, and olive oils.

• Main Outcome Measures: The principal outcomes analyzed were all-cause mortality, cardiovascular disease (CVD) mortality, and cancer mortality.

• Statistical Analysis: Cox regression models estimated mortality while adjusting for age, body mass index (BMI), smoking, physical activity, total energy intake, and dietary quality.

Does Butter Increase Mortality Risk?

During 33 years of follow-up, 50932 participants died, including 12241 from cancer and 11240 from cardiovascular disease.

• High Butter Consumption:

  • Participants consuming the most butter had a 15% higher all-cause mortality risk (HR: 1.15; 95% CI: 1.08-1.22; P < 0.001).

  • Cancer mortality risk increased by 12% for every additional 10 grams of daily butter intake.

• High Plant-Based Oil Consumption:

  • Participants consuming the most plant-based oils had a 16% lower all-cause mortality risk (HR: 0.84; 95% CI: 0.79-0.90; P < 0.001).

  • An additional 10 grams of plant-based oil daily reduced cancer mortality risk by 11% and cardiovascular mortality risk by 6%.

• Replacing Fats:

  • Replacing 10 grams of butter daily with plant-based oils reduced all-cause mortality risk by 17% and cancer mortality risk by 17%.

Potential Limitations and Criticisms

Although described by the researchers as well designed, the study has limitations:

• Participants were predominantly white healthcare professionals, which may limit applicability to broader, more diverse populations.

• Only mortality was assessed, so further research is needed into specific disease risks and how they develop.

• The health effects of cooking methods also require investigation. High-temperature cooking in particular may oxidize plant-based oils and generate harmful compounds.

Conclusion: Should We Choose Butter or Plant-Based Oils?

The findings support existing dietary recommendations:

• Choose unsaturated rather than saturated fats. Increase consumption of plant-based oils, particularly olive and corn oils.

• Read ingredient lists on packaged foods carefully and choose healthy fats.

• Pay attention to cooking methods. Low-temperature cooking or uncooked use may be recommended to preserve plant-based oils' nutritional properties.

In conclusion, while this study shows that long-term butter consumption increases all-cause and cancer mortality risk, it clearly identifies plant-based oils as a healthier alternative. People should therefore review their eating habits and become more informed about building a healthy, balanced diet.