(Photo by Patrycja Jadach on Unsplash+)
Swapping butter for plant oils could cut death risk by 17%
In a nutshell
- People who consume more butter have a 15% higher risk of death, while those who use more plant oils have a 16% lower mortality risk, according to a 33-year Harvard study.
- Simply replacing about 2 teaspoons of butter with plant oils daily could reduce your risk of death by 17%, with olive, soybean, and canola oils showing the strongest benefits.
- While butter used in baking showed no significant risks, butter spread directly on foods was linked to higher mortality — suggesting where and how you use butter matters.
BOSTON — Butter may make everything better—except, perhaps, your lifespan. A massive study by Harvard University and Mass General Brigham researchers tracking more than 220,000 Americans for 33 years shows that butter enthusiasts face a 15% higher risk of early death compared to those who used it sparingly. Meanwhile, plant oil aficionados enjoyed a 16% reduced risk of mortality. The battle of the fats has a clear winner, and it’s not the dairy option.
The study, published in JAMA Internal Medicine, brings some clarity to a long-standing dietary debate: does it matter whether you reach for butter or plant-based oils in your kitchen? The answer appears to be yes—and the difference could impact how long you live. Simply swapping about two teaspoons of butter with an equivalent amount of plant oil could reduce mortality risk by roughly 17%.
“It is well established that substituting saturated fatty acids with unsaturated fatty acids and eliminating trans fatty acids confers substantial health benefits, particularly in the prevention of cardiovascular disease,” the researchers write. But they also note that while “butter has been traditionally linked to adverse health outcomes, especially cardiovascular risk, recent studies have yielded mixed results on butter consumption and mortality.”
Butter vs. Plant Oils
This Harvard team analyzed detailed dietary information across three major studies—the Nurses’ Health Study, Nurses’ Health Study II, and the Health Professionals Follow-up Study—creating one of the most thorough examinations of fat consumption and mortality ever done.
The study tracked how much butter (both for spreading and cooking) and various plant oils (including olive, canola, soybean, corn, and safflower) participants consumed. Researchers collected this information using food surveys every four years, then calculated averages to better capture long-term eating patterns.
During the follow-up period, nearly 51,000 deaths occurred, including about 12,200 from cancer and 11,200 from heart disease. After accounting for factors like age, weight, physical activity, smoking, alcohol use, and overall diet quality, a clear pattern emerged: more butter linked to higher death rates, more plant oils linked to lower ones.
Not all plant oils performed equally. Olive, soybean, and canola oils were all linked to lower death risk, while corn and safflower oils didn’t show significant benefits.
Breaking Down the Health Impacts
For specific health outcomes, the research revealed that increasing plant oil consumption by about two tablespoons daily was linked to an 11% lower risk of cancer death and a 6% lower risk of heart disease death. Higher butter intake, meanwhile, was associated with a 12% increase in cancer death risk, though surprisingly, it didn’t show a significant connection to heart disease deaths.
One key insight is that dietary substitutions matter. It’s not just about eating less of certain foods but what you replace them with. The different health effects likely stem from the foods’ fat compositions. Butter contains mostly saturated fats, which can increase harmful cholesterol levels and promote inflammation. Plant oils, especially olive, canola, and soybean varieties, contain mostly unsaturated fats that can improve cholesterol levels and reduce inflammation.
What does this mean for everyday eating? The researchers suggest that “replacing 3 small pats of butter (approximately 15 g) with 1 tablespoon of plant-based oil (approximately 15 g) in the daily diet could contribute to lowering the risk of premature mortality.”
This doesn’t necessarily mean eliminating all butter. Interestingly, the study found that “butter used for baking and frying wasn’t significantly associated with mortality risk”—possibly because people use smaller amounts or consume it less frequently. The stronger association was with butter spread directly on foods or bread.
Making Simple Changes for Better Health
The good news is that making this switch doesn’t mean sacrificing flavor. Many plant oils, particularly olive oil, can enhance food taste while providing health benefits. For cooking, canola and soybean oils work well and offer beneficial fat profiles.
The findings help clarify sometimes confusing dietary advice about fats. Some recent reports have suggested butter might not be as harmful as once thought, while others have continued to recommend limiting saturated fat.
“Even cutting back butter a little and incorporating more plant-based oils into your daily diet can have meaningful long-term health benefits,” said Dr. Daniel Wang, an assistant professor in the Department of Nutrition at Harvard, in a statement. “
So the next time you reach for something to spread on toast or use in cooking, remember that this simple choice could affect your health more than you might think.
Paper Summary
Methodology
This research used data from three major studies: the Nurses’ Health Study (1990-2023), the Nurses’ Health Study II (1991-2023), and the Health Professionals Follow-up Study (1990-2023). The participants included women and men who didn’t have cancer, heart disease, diabetes, or neurodegenerative disease when the study began. In total, 221,054 adults participated, with average ages at the start ranging from 36.1 years (NHSII) to 56.3 years (HPFS). Researchers assessed participants’ diets using detailed food questionnaires every four years. These surveys asked about how often and how much people ate specific foods, what types of fats and oils they used, and what brands or types of oils they used for cooking and at the table. To capture long-term eating patterns and reduce measurement errors, researchers calculated average intakes of butter and plant oils across all dietary assessments during each 4-year period. Participants were followed for up to 33 years, with deaths identified through the National Death Index and other sources. Doctors classified causes of death based on death certificates and medical records.
Results
Over more than 5.4 million person-years of follow-up, researchers documented 50,932 deaths, including 12,241 from cancer and 11,240 from heart disease. After adjusting for various factors, participants who ate the most butter had a 15% higher risk of total mortality compared to those who ate the least. In contrast, those who consumed the most plant-based oils had a 16% lower mortality risk compared to those who consumed the least. When examining specific plant oils, higher intakes of canola, soybean, and olive oils were all linked to lower total mortality. Looking at specific causes of death, every 10-gram daily increase in plant oil consumption was associated with an 11% lower risk of cancer mortality and a 6% lower risk of heart disease mortality. Higher butter intake was associated with a 12% increase in cancer mortality but showed no significant association with heart disease mortality. In substitution analyses, replacing 10 grams of butter daily with an equivalent amount of plant oils was associated with a 17% reduction in total mortality and a 17% reduction in cancer mortality.
Limitations
Despite its strengths, the study has some limitations. First, dietary information from food questionnaires can contain measurement errors, which typically weaken associations rather than strengthen them. While researchers used averages over time to reduce short-term variations, some misreporting is inevitable. Second, reverse causation could occur—people might change their diets after developing health problems. Researchers addressed this by excluding participants with major chronic diseases at the start and stopping dietary updates after diagnoses of diabetes, stroke, or cancer. They also ran analyses using an 8-year lag and baseline diet only, which produced similar results. Third, participants might have confused margarine with butter due to their similar appearance. Additionally, despite adjusting for many factors, some residual confounding may remain. Lastly, participants were predominantly white healthcare professionals, which may limit how broadly the findings apply, though this demographic homogeneity helps reduce socioeconomic confounding.
Discussion and Takeaways
This comprehensive study provides strong evidence that the type of fat we consume can significantly impact mortality risk. The positive association between butter consumption and total and cancer mortality, along with the inverse association between plant-based oil consumption and mortality, supports current dietary guidelines recommending replacing saturated fats with unsaturated fats. The substitution analyses are particularly valuable, showing that replacing butter with plant-based oils could substantially reduce mortality risk. These results align with previous research on fatty acids and health outcomes but go further by examining specific food sources of fats and their relationships with mortality. The stronger associations observed with cumulative dietary data compared to baseline data highlight the importance of sustained dietary patterns over time. The study also found differences among plant-based oils, with olive, soybean, and canola oils showing beneficial effects, while corn and safflower oils showed no significant associations. This suggests that the specific fatty acid composition and other bioactive compounds in these oils may play important roles in their health effects. The practical implication is that relatively small dietary changes, such as replacing a few teaspoons of butter with plant-based oils, could meaningfully impact health and longevity.
Funding and Disclosures
The study was supported by research grants from the National Institutes of Health (multiple grant numbers provided). Dr. Guasch-Ferré reported grants from the Novo Nordisk Foundation and the International Nut and Dried Fruit Council outside the submitted work. Dr. Willett and Dr. Stampfer reported grants from the National Institutes of Health during the conduct of the study. The National Institutes of Health had no role in the design and conduct of the study; collection, management, analysis, and interpretation of the data; preparation, review, or approval of the manuscript; and decision to submit the manuscript for publication.
Publication Information
The study, titled “Butter and Plant-Based Oils Intake and Mortality,” was published online in JAMA Internal Medicine on March 6, 2025 (doi:10.1001/jamainternmed.2025.0205). The authors include Yu Zhang, Katia S. Chadaideh, Yanping Li, Yuhan Li, Xiao Gu, Yuxi Liu, Marta Guasch-Ferré, Eric B. Rimm, Frank B. Hu, Walter C. Willett, Meir J. Stampfer, and Dong D. Wang from various departments at Harvard T.H. Chan School of Public Health, Brigham and Women’s Hospital, Harvard Medical School, and other affiliated institutions.
