Which is Better for Longevity: Plant-Based Oil or Butter? New Research Reveals the Answer

A new study has revealed that eating more plant oils and less butter could lower mortality risk. 

The finding comes amid a growing sentiment on social media—bolstered by comments from U.S. Secretary of Health and Human Services Robert F. Kennedy, Jr.—that seed oils, a type of plant oil, are unhealthier than butter, beef tallow, and other animal fats.

The research, published in JAMA Internal Medicine, specifically found that people who substituted plant-based oils like soybean, canola, or olive for butter had a significantly lower risk of death from any cause.

Though plenty of previous research has pointed to the healthfulness of plant oils compared to butter, study author Yu Zhang, MBBS, a researcher at the Channing Division of Network Medicine at Brigham and Women’s Hospital, told Health that the new study differs from older ones in some key ways.

“What sets our study apart is its scale and methodology,” he said.

Besides using a large sample size—over 221,000 U.S. adults—the research team periodically monitored people’s diets for over 30 years. Using this data, they were able to perform direct substitution analysis, a research technique that isolates the impact of a single dietary change.

“This design provides a clearer basis for dietary recommendations than many previous studies that only looked at fats in aggregate,” Zhang said.

It only takes a glance to see that plant oils and butter are two distinct foods. Butter holds its shape at room temperature, while oil remains a liquid. This difference in solidity is an indicator of an underlying nutritional difference.

Saturated fats, prevalent in butter, are solid at room temperature. Unsaturated fats, the kind highest in most plant-based oils, are liquid at room temperature.

Unsurprisingly, then, butter is much higher in saturated fat than most plant oils. According to Roberta H. Anding, MS, RD/LD, an assistant professor at Baylor College of Medicine, butter contains 70% saturated fat, while olive oil contains 14%, soybean oil 16%, and canola oil 7%. 

However, the nutritional differences between butter and plant-based oils don’t stop there. Unlike butter, plant-based oils also contain antioxidants, including vitamin E, Emily A. Johnston, PhD, a research assistant professor at NYU Langone Health’s Department of Medicine, told Health.

To conduct the JAMA Network study, Zhang and fellow researchers used data from over 221,000 people enrolled in the Nurses' Health Study, Nurses' Health Study II, and Health Professionals Follow-up Study. 

These three longitudinal studies have been ongoing for decades. Every four years for up to 33 years, participants provided responses to diet questionnaires that revealed how much they eat of specific foods, including butter and plant-based oils like canola, olive, soybean, corn, and safflower.

By analyzing the amount of butter and plant oils people consumed and the incidence and causes of death, the researchers reached several noteworthy conclusions. 

People who ate the most butter had a 15% higher risk of dying than those who ate the smallest amounts. On the other hand, people whose diets included the most plant-based oils had 16% lower chances of death than those who ate the least.

Substituting plant-based oils for butter also appeared to significantly affect mortality. Replacing 10 grams per day (about two teaspoons) of butter with an equivalent amount of plant-based oils was associated with an estimated 17% reduction in total mortality and cancer death.

It’s worth noting, though, that the study did have a few limitations. Because it relied on self-reported food frequency questionnaires, it couldn’t verify people’s diets with 100% accuracy. Additionally, the researchers noted that subjects may have sometimes mistakenly reported margarine intake as butter because the two foods look so much alike.

The saturated fat that gives butter its firmness is the likely culprit behind its negative impact on mortality. Many studies have linked high intake of saturated fat with health problems like heart disease, weight gain, and high cholesterol.         

Conversely, the healthier fats in plant oils could protect against some chronic health conditions.

“Plant‐based oils contain unsaturated fats that help lower LDL cholesterol and reduce inflammation, both of which are linked to a lower risk of heart disease and cancer,” Zhang explained.

In contrast, butter’s high saturated fat content may contribute to these conditions. “Thus, switching from butter to plant‐based oils may help keep your heart and overall body healthier over time,” he said.

Johnston explained that the antioxidants found in plant-based oils have the ability to protect the body from oxidative damage and decrease inflammation. She stated, "These qualities can lower the chances of developing heart disease, diabetes, and certain types of cancer."

Although plant oils may not always be a direct replacement for butter in every cooking scenario (most people would likely prefer butter on toast rather than oil), there are numerous innovative methods to substitute or reduce the use of butter. Consider testing out these strategies recommended by experts: