Using certain vegetable oils instead of butter may help people live longer, healthier lives, according to a new study.
The study, published Thursday in JAMA Internal Medicine, builds on a large body of research showing the health benefits of olive oil in particular, and on recent studies that have complicated conventional wisdom about butter’s links with heart disease and overall mortality risk. By tracking dietary and mortality data of 221,054 adults over more than 30 years, the study authors say they’ve gained useful insights into the long-term consequences of the particular kinds of fats we eat.
“The takeaway is very simple: Higher intake of butter is associated with higher risk of premature death, and higher intake of plant-based oil is associated with lower risk of premature death,” said Daniel Wang, the study’s corresponding author and an assistant professor of medicine at Brigham and Women’s Hospital. People who ate the most butter had a 15% higher mortality risk compared to people who ate the least butter, while people who ate the most plant-based oils had a 16% lower mortality risk.
The study also found that swapping just 10 grams (less than a tablespoon) of butter a day with an equivalent amount of plant-based oils could lower risk of death overall by 17%, as well as lowering risk of death from cancer by 17%. “If you can replace [butter], you can enjoy quite a bit of health benefit in terms of major chronic diseases,” Wang said.
The JAMA study’s findings about the benefits of canola and soybean oil challenge the thinking among those who try to avoid so-called seed oils, including canola and soybean, because of concerns over their possible links with chronic disease. A number of people involved in the Make America Healthy Again movement, including health secretary Robert F. Kennedy Jr., have suggested it’s better to eschew vegetable oils made with industrial processes and recommended butter along with alternatives like coconut oil and beef tallow as substitutes.
But the consensus among nutrition experts, bolstered by this new study, is that plant oils are generally preferable to animal fats.
Like most nutrition studies, this was an observational trial rather than randomized. The study’s participants filled out surveys every four years about what they ate and how much. Most of them were white health professionals, which the study’s authors note as a limitation that may make the results less generalizable.
Wang acknowledged that participants may have had a hard time recalling with complete accuracy what they ate over a four-year period, but said the authors found that errors were non-differential, meaning that people were equally likely to make such errors regardless of their disease risk. Moreover, he said via email, “this type of error tends to weaken associations, meaning the results reported in the paper are actually conservative estimates of the relationship between butter and plant oil intake and mortality, and very unlikely to be false positive findings.”
Even when controlling for the possibility that people who ate more butter had lower-quality diets than people who ate more vegetable oils, the study still found an association between higher butter consumption and greater mortality risk. Among vegetable oils, olive oil, canola oil, and soybean oil specifically were associated with lower mortality risk.
“This new research adds to a large body of science on the health benefits of these plant oils, whose positive effects on cholesterol levels, blood glucose, and cardiovascular disease have been demonstrated in numerous large observational studies and dozens of randomized trials,” Dariush Mozaffarian, a cardiologist and director of the Food is Medicine Institute at Tufts University who was not involved with the study, said in an email. He noted that the study found no evidence that corn and safflower oils, which were less popular choices among participants, are either helpful or harmful to health.
Mozaffarian co-authored a buzzy 2016 meta-analysis that found butter was largely a neutral food in terms of its long-term impact on mortality, cardiovascular disease, and cancer. He questioned the new study’s conclusions on butter, observing that among people in the study who had healthier diets overall, butter had no association with higher mortality risk. To him, that suggests “butter has minimal effects if you otherwise eat a healthy diet.”
“Overall, butter is probably pretty neutral for health — worse than plant oils, fruits, or nuts, but better than the white bread it’s spread upon,” Mozaffarian said.
The new study and the long-running debate over fats have implications for health equity, said the authors of a commentary published alongside the study.
“Analyses excluding olive oil indicated a consistent inverse association between substituting plant-based oils for butter and reduced mortality risk,” write authors Yong-Moon Mark Park of the University of Arkansas’ school of public health and Yikyung Park of Washington University School of Medicine. “This suggests that more affordable options, such as canola and soybean oils, may serve as accessible alternatives to olive oil, which tends to be more expensive.”
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