Bad news for butter lovers: a Harvard study published in JAMA Internal Medicine looked at decades of data to see how butter and plant oils affect the risk of dying.
The main finding? People who ate more butter had a higher chance of death, while those who ate more plant oils had a lower chance. Swapping about a tablespoon of butter each day for plant oil might help you live longer.
Butter vs. Plant Oils
Researchers grouped people based on how much butter or plant oils they reported using. Over up to 33 years, those eating the most butter had a 15% higher risk of death than those eating the least. Those eating the most plant oils had a 16% lower risk of death than those eating the least.
Higher butter intake was linked to more cancer deaths. Higher plant-oil intake was linked to fewer deaths from cancer and heart problems like heart attack or stroke.
Out of five plant oils studied, soybean, canola, and olive oil showed clear benefits. Modeling suggested that replacing about 10 grams of butter (just under a tablespoon) with one of these oils each day was tied to fewer overall deaths and fewer cancer deaths.
Why Plant Oils Help
Butter has almost no essential fatty acids and some unhealthy trans fat. In contrast, oils like olive, canola, and soybean are rich in unsaturated fats, essential fatty acids, and antioxidants. These nutrients can improve cholesterol levels, lower blood fats, and reduce inflammation.
This advice matches U.S. dietary guidelines and American Heart Association suggestions for lowering disease risk. You can still enjoy a little butter for flavor, but use liquid plant oils whenever you can for cooking and at the table.
Try different oils—extra virgin olive, mustard, or sesame—to find flavors you like. You can also mix a bit of butter with oil for extra taste.
Study Strengths and Limits
The study used food questionnaires answered every four years by more than 221,000 adults. It adjusted for factors such as age, exercise, smoking, and family health history.
As an observational study, it can’t prove cause and effect, and most participants were white health professionals, so the results may not apply to everyone. Still, the large number of people and long follow-up time make the findings meaningful.