Cooking Oils

CATEGORY: EATING FOR HEART HEALTH

In a study that followed more than 220,000 adults for up to three decades, swapping a small daily amount of butter for plant-based oils — such as olive, soybean, or canola oil — was linked to roughly a 17% lower risk of dying during the study period. People who ate the most butter had modestly higher death rates than those who ate the least, while the pattern ran the opposite way for plant oils.¹

What the Study Found

Researchers compared people by how much butter or plant oil they usually ate. Those in the highest butter group had about 15% higher total mortality — death from any cause — than those in the lowest, while those eating the most plant-based oils had about 16% lower total mortality than those eating the least. When the researchers modeled replacing a small daily amount of butter (roughly two teaspoons) with the same amount of plant oil, that swap was associated with about 17% lower total mortality and about 17% lower death from cancer.¹

How the Study Worked

The findings pool three long-running U.S. studies — the Nurses’ Health Study, Nurses’ Health Study II, and the Health Professionals Follow-up Study — totaling 221,054 adults tracked for as long as 33 years. Every four years, participants reported their eating habits on detailed food questionnaires, and deaths were identified through the National Death Index, with causes confirmed from medical records. Because the outcome here is who lived longer over decades, that long follow-up and repeated diet check-ins are central to the result, not background detail. This was an observational study, meaning it tracks real-world patterns and can show associations but cannot prove that the fats themselves caused the difference.¹

Why the Type of Fat May Matter

Butter is high in saturated fat, which tends to raise LDL cholesterol — the “bad” cholesterol that can build up in artery walls. Plant-based oils are rich in unsaturated fats, which are generally linked to healthier cholesterol levels and lower inflammation. That biological difference is the leading explanation researchers offer for why the two types of fat lined up with such different long-term outcomes, though a single study like this cannot confirm the mechanism.¹

Keeping It in Perspective

Because this is observational, people who reached for plant oils may have differed in other ways that affect health, even though the researchers adjusted for many lifestyle factors. The links were also stronger for butter eaten as a spread or in cooking than for the smaller amounts used in baking. The takeaway is not that butter is dangerous in any single meal, but that, across many years, the kind of fat that dominates a person’s diet appears to track with meaningfully different risks.

Key Takeaways

• Over up to 33 years, higher butter intake was linked to about 15% higher risk of death, and higher plant-oil intake to about 16% lower risk.
• Modeling a small daily swap of butter for plant oils was associated with roughly 17% lower total and cancer mortality.
• Because the study is observational, it shows associations only and cannot prove cause and effect.
• If you are weighing changes to the fats in your diet — especially alongside cholesterol or heart concerns — your doctor or a registered dietitian can help you sort out what fits your health.

References

1. Zhang Y, Chadaideh KS, Li Y, et al. Butter and Plant-Based Oils Intake and Mortality. JAMA Internal Medicine. 2025;185(5):549–560. link