Replacing butter with plant-based oils like olive oil may reduce risk of dying by 17 percent

Image credit – Mass General Brigham Harvard School of Public Health

CANCER DIGEST – March 15, 2025 – People who consume plant-based oils such as olive oil have a 17 percent lower risk of dying compared to people who consume butter in their daily diet, according to a new study by researchers at the Mass General Brigham Harvard School of Public Health.

The study analyzed diet and health data collected over 30 years from 200,000 people. The researchers found that people whose daily intake of of soybean, canola and olive oil was associated with lower total, cancer, and cardiovascular disease mortality. By contrast the data showed that butter intake was associated with increased risk of total and cancer deaths.The results were published in the March 6, 2025 journal JAMA Internal Medicine.

"What's surprising is the magnitude of the association that we found," said study lead author Yu Zhang in a press release."We saw a 17 percent lower risk of death when we modeled swapping butter with plant-based oils in daily diet. That is a pretty huge effect on health."

The difference between plant-based oils and butter is the types of fatty acids they contain. Butter is a saturated fatty acid, while plant-based oils have more unsaturated fatty acids. Previous studies have looked at personal diet at certain points in time in small populations. This study analyzed dietary data from 221,054 participants in the Nurses’ Health Study, Nurses’ Health Study II, and the Health Professionals Follow-up Study. 

Participants in these studies fill out standardized questionnaires every four years answering detailed questions about how often they consumed certain types of food. Using this data, the researchers were able to estimate consumption of butter, margarine, margarine blends and butter used in frying and baking foods. They were also able to estimate consumption of plant oils used in frying sautéing, baking and salad dressings.

Using that data, the researchers compared participants who had died and their causes of death. They found that participants who ate the most butter had a 15 percent higher risk of dying than those who ate the least amount of butter. On the other hand, the data also showed that those ate the most plant-based oils had a 16 percent lower risk of death compared to those who ate the least amount of such oils.

When they ran a computer model that mimicked swapping 10 grams (about a tablespoon) of plant oils for the equivalent amount of butter, cancer deaths and overall mortality was reduced by 17 percent.

"From a public health perspective," co-author Daniel Wang, MD, ScD said in a press release. "This is a substantial number of deaths from cancer or from other chronic diseases that could be prevented."

The chief limitation of the study is that the data was collected from health professionals, who may not be representative of the population as a whole.

Source: Mass General Brigham press release