Abstract
The relationship between butter and plant-based oil intakes and mortality remains unclear, with conflicting results from previous studies. Long-term dietary assessments are needed to clarify these associations. OBJECTIVE To investigate associations of butter and plant-based oil intakes with risk of total and cause-specific mortality among US adults. DESIGN, SETTING, AND PARTICIPANTS This prospective population-based cohort study used data from 3 large cohorts: the Nurses’ Health Study (1990-2023), the Nurses’ Health Study II (1991-2023), and the Health Professionals Follow-up Study (1990-2023). Women and men who were free of cancer, cardiovascular disease (CVD), diabetes, or neurodegenerative disease at baseline were included. EXPOSURES Primary exposures included intakes of butter (butter added at the table and from cooking) and plant-based oil (safflower, soybean, corn, canola, and olive oil). Diet was assessed by validated semiquantitative food frequency questionnaires every 4 years. MAIN OUTCOMES AND MEASURES Total mortality was the primary outcome, and mortality due to cancer and CVD were secondary outcomes. Deaths were identified through the National Death Index and other sources. A physician classified the cause of death based on death certificates and medical records. RESULTS During up to 33 years of follow-up among 221 054 adults (mean [SD] age at baseline: 56.1 [7.1] years for Nurses’ Health Study, 36.1 [4.7] years for Nurses’ Health Study II, and 56.3 [9.3] years for Health Professionals Follow-up Study), 50 932 deaths were documented, with 12 241 due to cancer and 11 240 due to CVD. Participants were categorized into quartiles based on their butter or plant-based oil intake. After adjusting for potential confounders, the highest butter intake was associated with a 15% higher risk of total mortality compared to the lowest intake (hazard ratio [HR], 1.15; 95% CI, 1.08-1.22; P for trend < .001). In contrast, the highest intake of total plant-based oils compared to the lowest intake was associated with a 16% lower total mortality (HR, 0.84; 95% CI, 0.79-0.90; P for trend < .001). There was a statistically significant association between higher intakes of canola, soybean, and olive oils and lower total mortality, with HRs per 5-g/d increment of 0.85 (95% CI, 0.78-0.92), 0.94 (95% CI, 0.91-0.96), and 0.92 (95% CI, 0.91-0.94), respectively (all P for trend < .001). Every 10-g/d increment in plant-based oils intake was associated with an 11% lower risk of cancer mortality (HR, 0.89; 95% CI, 0.85-0.94; P for trend < .001) and a 6% lower risk of CVD mortality (HR, 0.94; 95% CI, 0.89-0.99; P for trend = .03), whereas a higher intake of butter was associated with higher cancer mortality (HR, 1.12; 95% CI, 1.04-1.20; P for trend < .001). Substituting 10-g/d intake of total butter with an equivalent amount of total plant-based oils was associated with an estimated 17% reduction in total mortality (HR, 0.83; 95% CI, 0.79-0.86; P < .001) and a 17% reduction in cancer mortality (HR, 0.83; 95% CI, 0.76-0.90; P < .001). CONCLUSIONS AND RELEVANCE In this cohort study, higher intake of butter was associated with increased mortality, while higher plant-based oils intake was associated with lower mortality. Substituting butter with plant-based oils may confer substantial benefits for preventing premature deaths.
Generated Summary
This prospective population-based cohort study examined the associations of butter and plant-based oil intakes with mortality among US adults. The study used data from the Nurses’ Health Study (1990-2023), the Nurses’ Health Study II (1991-2023), and the Health Professionals Follow-up Study (1990-2023). The main outcomes were total mortality, with secondary outcomes including mortality due to cancer and cardiovascular disease (CVD). Dietary intake was assessed using validated semiquantitative food frequency questionnaires every 4 years. The research aimed to clarify the relationships between butter and plant-based oil intakes and mortality, given conflicting results from previous studies, and to investigate whether substituting butter with plant-based oils could confer substantial benefits for preventing premature deaths. The study included 221,054 adults with up to 33 years of follow-up, with detailed analyses and adjustments for potential confounders.
Key Findings & Statistics
- During up to 33 years of follow-up among 221 054 adults, 50 932 deaths were documented, with 12 241 due to cancer and 11 240 due to CVD.
- The highest butter intake was associated with a 15% higher risk of total mortality (HR, 1.15; 95% CI, 1.08-1.22; P for trend < .001) compared to the lowest intake.
- The highest intake of total plant-based oils compared to the lowest intake was associated with a 16% lower total mortality (HR, 0.84; 95% CI, 0.79-0.90; P for trend < .001).
- Higher intakes of canola, soybean, and olive oils were associated with lower total mortality, with HRs per 5-g/d increment of 0.85 (95% CI, 0.78-0.92), 0.94 (95% CI, 0.91-0.96), and 0.92 (95% CI, 0.91-0.94), respectively (all P for trend < .001).
- Every 10-g/d increment in plant-based oils intake was associated with an 11% lower risk of cancer mortality (HR, 0.89; 95% CI, 0.85-0.94; P for trend < .001) and a 6% lower risk of CVD mortality (HR, 0.94; 95% CI, 0.89-0.99; P for trend = .03).
- Higher intake of butter was associated with higher cancer mortality (HR, 1.12; 95% CI, 1.04-1.20; P for trend < .001).
- Substituting 10-g/d intake of total butter with an equivalent amount of total plant-based oils was associated with an estimated 17% reduction in total mortality (HR, 0.83; 95% CI, 0.79-0.86; P < .001) and a 17% reduction in cancer mortality (HR, 0.83; 95% CI, 0.76-0.90; P < .001).
Other Important Findings
- In the substitution analysis, replacing 10 g/d of total butter intake with an equivalent amount of total plant-based oil was associated with an estimated 17% reduction in total mortality (HR, 0.83; 95% CI, 0.79-0.86; P < .001), a 17% reduction in cancer mortality (HR, 0.83; 95% CI, 0.76-0.90; P < .001), and a 6% reduction in CVD mortality, although the latter was not statistically significant.
- The HRs of total mortality when substituting 10 g/d of total butter with plant oils excluding olive oil, soybean oil, and olive oil were 0.83 (95% CI, 0.79-0.88), 0.85 (95% CI, 0.80-0.91), and 0.81 (95% CI, 0.77-0.84), respectively.
- Higher intakes of canola oil, soybean oil, and olive oil were associated with lower total mortality, with HRs per 5-g/d increment of 0.85 (95% CI, 0.78-0.92), 0.94 (95% CI, 0.91-0.96), and 0.92 (95% CI, 0.91-0.94), respectively (all P for trend < .001).
Limitations Noted in the Document
- The study relies on dietary data collected through FFQs, which are subject to measurement errors that may underestimate associations.
- Reverse causation is a potential concern, as participants might have altered their diets after developing chronic diseases.
- The study population was predominantly White and consisted mainly of health care professionals, which may limit the generalizability of the findings.
- Some plant-based oil intakes were estimated, which may have introduced some degree of error.
- The lack of significant associations between butter used in baking/frying and total mortality may be attributed to the relatively small quantities of butter used in these ways.
Conclusion
The study concluded that higher butter intake was associated with increased total and cancer mortality, while higher plant-based oils intake was associated with lower mortality. The study highlights the need to consider food sources when assessing health effects, as previous studies often failed to explicitly identify comparison foods. The results support current dietary recommendations to replace animal fats like butter with nonhydrogenated vegetable oils, particularly olive, soy, and canola oil. These findings align with dietary guidelines advocating for reducing saturated fat intake and replacing it with polyunsaturated and monounsaturated fats to lower the risk of chronic disease. The study emphasizes that replacing 3 small pats of butter (approximately 15 g) with 1 tablespoon of plant-based oil (approximately 15 g) in the daily diet could contribute to lowering the risk of premature mortality. Further studies are warranted to uncover the molecular mechanisms underlying the distinct metabolic effects of butter and plant-based oils.