Decades of research have demonstrated the health benefits of eliminating trans fats and replacing saturated fats with unsaturated fats, particularly in reducing the risk of cardiovascular disease (CVD). Plant-based oils, which are rich in unsaturated fats, and butter, which is high in saturated fats, may have different health effects. Although butter has been associated with CVD, recent research has yielded conflicting results. In contrast, plant-based oils improve the lipid profile and reduce inflammation. The previous studies have not adequately assessed the long-term correlation of plant-based oil and butter consumption with mortality. This was clearly demonstrated in a recent prospective population-based study published in JAMA Internal Medicine.
In this study, data were collected from the three large U.S. cohorts: Health Professionals Follow-up Study (HPFS, 1990-2023), Nurses’ Health Study (NHS, 1990-2023), and Nurses’ Health Study II (NHSII, 1991-2023). Individuals with a history of diabetes, CVD, Neurodegenerative diseases, cancer, those lacking baseline data on plant-based oils and butter intake, and those who declared unrealistic energy intake were excluded.
Dietary consumption of plant-based oils (Olive, corn, Soybean, safflower, and canola oils) and butter were evaluated using validated semiquantitative food frequency questionnaires (FFQ) at baseline and every four years. The primary endpoint was total mortality, and the secondary endpoint was mortality because of CVD and cancer. This study had a follow-up period of 33 years. All death cases were detected using the National Death Index and additional sources. All statistical analysis was conducted through SAS version 9.4.
A total of 221,054 U.S. adults were included during the follow-up time. The mean age of participants at baseline was 56.1±7.1 years in NHS (all female = 53,415), 36.1±4.7 years in NHSII (all female = 77,583), and 56.3±9.3 years in HPFS (all male = 22,312). Additionally, 50,932 death cases were reported, including 11,240 due to CVD and 12,241 due to cancer. All participants were divided into four levels according to their intake of butter or plant-based oils.
After adjusting for potential confounders, the participants with higher butter consumption (level 4) had a 15% increased risk of total mortality compared to those with lower consumption (level 1) with a hazard ratio (HR) of 1.15 (95% confidence interval [CI], 1.08-1.22) and P < 0.001. Conversely, the highest consumption of plant-based oils had a 16% decrease in total mortality compared to the lowest intake with HR of 0.84 (95% CI, 0.79-0.90) and P < 0.001.
A statistically significant difference was observed between the highest level of Soybean, olive, and canola oil consumption and a lower total mortality outcome. The HR per 5-g/day increase was 0.85 (95% CI, 0.78-0.92) for canola oil, 0.94 (95% CI, 0.91-0.96) for Soybean oil, and 0.92 (95% CI, 0.91-0.94) for olive oil with overall P < 0.001.
Moreover, a 10-g/day increase in plant-based oil consumption was linked to an 11% lower risk of cancer mortality with an HR of 0.89 (95% CI, 0.85-0.94 and P < 0.001), whereas a 6% lower risk of CVD mortality with HR of 0.94 (95% CI, 0.89-0.99 and P = 0.03). However, higher consumption of butter was associated with an increased risk of cancer mortality with HR of 1.12 (95% CI, 1.04-1.20) and P < 0.001.
Replacing 10 g/day of butter with an equivalent quantity of plant-based oils was correlated with a determined 17% decrease in total mortality with HR of 0.83 (95% CI, 0.79-0.86, P < 0.001) and as well as 17% decrease in cancer mortality with HR of 0.83 (95% CI, 0.76-0.90, P < 0.001).
This study’s limitations include measurement errors in dietary data, potential reverse causation, misreported butter intake, residual confounding, and limited generalizability.
In conclusion, this study demonstrated that higher consumption of butter was linked to increased total and cancer mortality, whereas higher intake of plant-based oils was linked to decreased total, CVD, and cancer mortality. Replacing butter with plant-based oils, particularly olive, canola, and soybean oils, may significantly reduce the risk of premature death. These findings support the current dietary guidelines recommending the substitution of animal fats (butter) with vegetable oils (unsaturated fats), especially canola, olive, and Soybean oils. Future research is needed to explore the mechanisms driving the differing metabolic effects of butter and plant-based oils.
Reference: Zhang Y, Chadaideh KS, Li Y, et al. Butter and Plant-Based Oils Intake and Mortality. JAMA Intern Med. 2025. doi:10.1001/jamainternmed.2025.0205
