A cohort study spanning over three decades has found that higher consumption of butter may be associated with increased mortality, while greater intake of plant-based oils may correlate with a reduced risk of mortality.

The study, published in JAMA Internal Medicine, provided compelling evidence that substituting butter with plant-based oils could significantly reduce the risk of premature mortality. Investigators analyzed data from 221,054 adults across three major cohorts: the Nurses' Health Study (1990 to 2023), Nurses' Health Study II (1991 to 2023), and Health Professionals Follow-up Study (1990 to 2023). During the follow-up period of up to 33 years, 50,932 deaths were documented, including 12,241 from cancer and 11,240 from cardiovascular disease (CVD).

"After adjusting for potential confounders, the highest butter intake was associated with a 15% higher risk of total mortality compared to the lowest intake," the study authors reported. In stark contrast, "the highest intake of total plant-based oils compared to the lowest intake was associated with a 16% lower total mortality," they added.

Participants in the highest quartile of butter consumption showed a hazard ratio (HR) of 1.15 for total mortality compared with those in the lowest quartile. Conversely, those in the highest quartile of plant-based oil consumption demonstrated an HR of 0.84.

The study found statistically significant associations between higher intakes of specific plant-based oils and lower mortality risk. Per 5-g/day increment, canola oil showed an HR of 0.85, soybean oil 0.94, and olive oil 0.92, all with P for trend < .001.

For cause-specific mortality, each 10-g/day increment in plant-based oils was associated with an 11% lower risk of cancer mortality and a 6% lower risk of CVD mortality. Higher butter intake correlated with increased cancer-related mortality but showed no statistically significant association with CVD mortality.

In the substitution analysis, replacing 10-g/day of total butter intake with an equivalent amount of total plant-based oils was associated with an estimated 17% reduction in total mortality and a 17% reduction in cancer-related mortality.

"Substituting butter with plant-based oils, particularly olive, soybean, and canola oils, may confer substantial benefits for preventing premature deaths," the study authors concluded.

The study's methodology included repeated assessments of dietary intake using validated semiquantitative food frequency questionnaires every 4 years. Total butter intake was calculated by totaling consumption from three sources: butter from butter-margarine blend, spreadable butter added to food and bread, and butter used in baking and frying. Plant-based oil intake calculations included corn, safflower, soybean, canola, and olive oils.

The findings aligned with previous research establishing that substituting saturated fatty acids with unsaturated fatty acids conferred health benefits, particularly in preventing cardiovascular disease. The study provided strong evidence supporting current dietary recommendations to reduce animal fat consumption and increase intake of plant-based oils high in unsaturated fats.

Disclosures can be found in the study.