Switching out butter for plant-based oil may lower overall mortality by 17%, study finds

A study suggests that people who consume plant-based oil instead of butter may experience beneficial health effects and a lower risk of premature death.

Investigators from Mass General Brigham, Harvard T.H. Chan School of Public Health, and the Broad Institute of MIT and Harvard led the US-based research.

The researchers examined diet and health data from 200,000 people followed for more than 30 years and found that higher intake of plant-based oils — especially soybean, canola, and olive oil — was associated with lower total, cancer, and cardiovascular disease mortality.

On the other hand, butter intake was associated with an increased risk of total and cancer mortality.

“What’s surprising is the magnitude of the association that we found — we saw a 17% lower risk of death when we modeled swapping butter with plant-based oils in daily diet. That is a pretty huge effect on health,” says study lead author Yu Zhang, MBBS, research assistant at the Channing Division of Network Medicine at Brigham and Women’s Hospital, a founding member of the Mass General Brigham healthcare system.

The results are published in JAMA Internal Medicine and presented simultaneously at the American Heart Association EPI/Lifestyle Scientific Sessions.

Key difference between butter and oil

Butter and oil are notably different in the types of fatty acids they contain. Butter is rich in saturated fatty acids, while plant-based oils have more unsaturated fatty acids.

While many studies have been conducted on dietary fatty acids, the authors of the paper say few have focused on their primary food sources, including butter and oils.

They add that previous studies have looked at a person’s diet at only one point in time and involved a small population, limiting their applicability to public health.

The study found that substituting 10 g of butter daily (less than a tablespoon) with equivalent calories of plant-based oils could lower cancer deaths and mortality by 17%.The new study analyzed dietary data from 221,054 participants in the Nurses’ Health Study (NHS), Nurses’ Health Study II (NHSII), and Health Professionals Follow-up Study (HPFS).

Every four years, they answered questions about how often they consumed certain types of food. The researchers used the data to estimate how much butter and plant oils they ate.

This study didn’t just examine butter. It considered all types of butter consumption, including blends, spreads, and butter used in home cooking and baking. Similarly, plant-based oil intake was calculated from its use in frying, sautéing, baking, and salad dressings.

The researchers also identified participants who had died and their causes of death. Using statistics to compare death rates across different diet intake levels, the researchers found that participants who ate the most butter had a 15% higher risk of dying than those who ate the least.

In contrast, those who ate the most plant-based oils had a 16% lower risk of death than those who ate the least.

“People might want to consider that a simple dietary swap — replacing butter with soybean or olive oil — can lead to significant long-term health benefits,” says corresponding author Daniel Wang, MD, ScD, of the Channing Division of Network Medicine at Brigham and Women’s Hospital.

“From a public health perspective, this is a substantial number of deaths from cancer or from other chronic diseases that could be prevented.”

Situation analysis 

The researchers also did a substitution analysis, miming how swapping butter for plant oils would impact health in a feeding trial. They found that substituting 10 g of butter daily (less than a tablespoon) with equivalent calories of plant-based oils could lower cancer deaths and mortality by 17%.

“Even cutting back butter a little and incorporating more plant-based oils into your daily diet can have meaningful long-term health benefits,” Wang says.

A significant limitation of the study is that the participants are mainly health professionals, so they might not represent the US population as a whole, the researchers highlight. In the future, they would like to study the biological mechanisms underlying why this dietary change has such a large impact.

A previous study revealed that US adults consume dangerous amounts of saturated fat and added sugar from unexpected food sources, beyond the usual suspects like cheese, soda, and desserts. To help address this, they are developing an app that accurately identifies these “nutrients of concern,” with early tests demonstrating the tool’s effectiveness in pinpointing key food contributors.

In moves to commercialize and scale up the production of functional and sustainable plant-based fats, California-based Checkerspot and AAK joined forces last year to develop fats and oils based on fermented microalgae.