By the time you finish reading this, another person somewhere in the world will have died—statistically speaking. Maybe from heart disease. Maybe from cancer. And, if they were big fans of slathering butter on their morning toast, there’s a good chance their dietary choices played a role.

A large-scale study tracked more than 220,000 adults for up to 33 years. It clearly found that higher butter consumption is associated with increased mortality. Meanwhile, swapping it out for plant-based oils could lower your risk of dying from all causes, including cancer and heart disease. Substituting just 10 grams (0.35 ounces) of butter with plant-based oils was associated with a 17% lower risk of mortality.

“In a sane world, this study would give the butter bros and anti-seed oil brigade pause for thought,” said Sarah Berry, Professor of Nutritional Sciences, King’s College London.

Butter really is bad for you

Butter has been a culinary staple for centuries. It’s a rich, calorie-dense food that provided essential fats and energy, especially in colder climates where plant-based oils were scarce. It also has a long shelf life (when stored properly) and is versatile in cooking and baking. Plus, let’s face it, it makes a lot of things taste better.

Public health recommendations around butter changed as studies started suggesting that it’s bad for your heart. Recently, however, it’s made a comeback with keto warriors and paleo enthusiasts hailing it as a “wholesome” source of fat. But biochemically speaking, butter is still packed with saturated fat—a known culprit in cardiovascular disease.

This study adds more evidence.

The meta-analysis analyzed the dietary habits of participants in several studies. These studies monitored Americans’ health and eating habits since the ’70s and ’80s. The results showed that those in the highest tier of butter consumption (around 13 grams a day—roughly three pats), have a 15% higher risk of dying from any cause compared to those in the lowest tier (barely touching the stuff). But if you were chugging plant-based oils, your risk of death was 16% lower.

“This study covered a wider range of plant oils than previous research to find that greater consumption of rapeseed oil, soybean oil or olive oil is associated with an overall lower risk of death.  It is positive to see other plant oils being considered in this way as olive oil has been a focus of much research in the past,” notes Louise Flanagan, Head of Research for the Stroke Association, who was not involved in the study.

“The study shows that high butter consumption is linked to increased cancer and total mortality, whereas plant-based oils are linked to a lower risk of overall mortality and death due to cardiovascular disease and cancer,” added Berry.

How butter affects your body

Butter isn’t poison. It’s not like a scoop of butter will kill you on the spot. But when you indulge in butter-laden meals, a chain reaction unfolds in your body that can have serious long-term consequences.

The high levels of saturated fat in butter flood your bloodstream, leading to an increase in low-density lipoprotein (LDL) cholesterol—the so-called “bad” cholesterol. Over time, this LDL can become oxidized, which damages artery walls and triggers inflammation, driving cardiovascular disease. As plaque accumulates in the arteries, the risk of heart attacks and strokes rises. Meanwhile, chronic inflammation doesn’t just affect the heart. It may also fuel cancer growth by creating an environment that supports the uncontrolled division of abnormal cells.

While butter may enhance the flavor of a meal, it could also be laying the groundwork for serious health risks.

“The link between diets high in saturated fat, particularly animal-based fat such as butter and lard, and higher mortality has been argued for decades. I have seen American adverts from the 1960s extolling the virtues of American housewives “polyunsaturating” their husbands when they come home from work. This is a fun historical reminder of the link between the food industry and dietary health messages, as well as showing how much woman have had to fight for social progress,” notes Parveen Yaqoob, professor of nutritional science at the University of Reading.

So giving up butter is clearly a healthy option. But here’s the thing: substituting it for plant oils is even healthier.

Plant oils are healthier, some more than others

Butter intake included any amount used in any form, including cooking, baking, and spreading on bread. Meanwhile, plant-based oils were mostly used for frying, sautéing, baking, or salads.

Olive oil, soybean oil, and canola oil showed the strongest benefits. This is likely due to their high content of unsaturated fats and anti-inflammatory properties. Unlike butter, which is rich in saturated fat and linked to higher LDL cholesterol and inflammation, these plant-based oils provide heart-healthy fats that help lower bad cholesterol, improve metabolic health, and reduce overall disease risk.

In fact, the benefits reported in this study were even higher than what researchers previously noticed.

“Butter is high in saturated fat, contains some trans fatty acids but is very low in polyunsaturated fats. Whereas unhydrogenated soybean, canola and olive oils are low in saturated fatty acids but high in unsaturated fats. Replacement of butter with these vegetable oils is well documented to lower blood cholesterol, particularly that associated with low density lipoprotein (LDL) by about 10%.”

“This change in LDL cholesterol would be predicted to reduce the relative risk of death by about 3%, which is much less than what was observed in this study. It remains possible that a higher intake of polyunsaturated fatty acids (especially linoleic acid) from the vegetable oil may have played a role in reducing risk by a variety of mechanisms,” said Tom Sanders, Professor emeritus of Nutrition and Dietetics, King’s College London.”

Some questions remain, but butter is a culprit

The research is very timely, Berry adds.

“Social media is currently awash with influencers promoting butter as a health food and claiming that seed oils are deadly. This large-scale, long-term study finds the reverse. The authors produce further evidence that seed oil consumption is linked to improved health and that butter – delicious as it is – should only be consumed once in a while.”

Granted, there are limitations to the study. The first is that this is a correlation-not-causation study (although there’s a lot of science suggesting causality as well). Then, the majority of participants were white and healthcare professionals, which may limit the generalizability of the findings. Furthermore, the study didn’t analyze whether consuming butter and plant-based oils had a neutralizing or additive effect on health outcomes. This is definitely something that could be considered in future studies.

Nutritional science is messy. The food industry complicates things further, funding studies that often contradict each other. But this particular research is as solid as it gets—spanning three massive cohorts over three decades.

Sure, more studies will come along. Maybe a future paper will argue that grass-fed, organic, blessed-by-a-monk butter is actually a health elixir. But for now, the evidence overwhelmingly suggests that if you care about longevity, it’s time to cut back on butter and go all-in on plant-based oils.

Your arteries—and future self—will thank you.

“This latest research provides strong additional data to support the ‘healthier fats’ theory. The research followed a large cohort of health workers in America over many years. The use of food frequency questionnaires means that we are relying on the participants to remember what they have eaten and how much, which we know can be an unreliable indicator of actual dietary patterns,” concludes Yaqoob.

The study was published in JAMA.