Butter Consumption’s Relationship to Cancer Mortality

Higher, long-term butter consumption is linked with increased total and cancer mortality, whereas plant-based oils may offer protective benefits, according to a prospective study of more than 200,000 adults.

These findings suggest that choosing plant-based oils over butter could help prevent premature deaths, lead author Yu Zhang, MBBS, of the Harvard T.H. Chan School of Public Health, Boston, and colleagues, reported.

“It is well established that substituting saturated fatty acids with unsaturated fatty acids and eliminating trans fatty acids confers substantial health benefits, particularly in the prevention of cardiovascular disease,” the investigators write in JAMA Internal Medicine. “However, major food sources of fatty acids contain a mix of fats, and dietary choices are typically based on whole foods rather than individual fatty acids.”

What have previous studies determined about the health risks and benefits of consuming various oils?

According to Anne McTiernan, MD, PhD, an internist and epidemiologist at Fred Hutch Cancer Center, Seattle, “Several studies have found higher intake of a plant-based diet with high vegetables and fruits, lower saturated fats, lower meats, lower processed food, and lower added sugars are associated with improved health effects, but there is no one [single] diet that stands above the others.” McTiernan was not involved with this current JAMA-IM study.

Rich in saturated fats, butter has traditionally been associated with an increased risk of cardiovascular disease; however, there may be more to the story, Zhang and colleagues noted. 

For example, a 2016 meta-analysis found that butter had a small or neutral association with cardiovascular disease, diabetes, and mortality, although comparisons were primarily made with the Western diet instead of healthier options.

The present study aimed to address this potential knowledge gap by directly comparing the health impacts of butter consumption with plant-based oils.

“This is a well-designed and conducted study,” McTiernan told Medscape Medical News. “[It is] useful because it looked at a simple food item — types and amounts of dietary fats — which if related to disease could be a relatively simple diet change for individuals to make. 

How did the new study evaluate the health impacts of consuming butter vs plant-based oils?

Zhang and colleagues analyzed prospective data from 221,054 adults in three large US cohorts: the Nurses’ Health Study (NHS, 1990-2023), Nurses’ Health Study II (NHSII, 1991-2023), and Health Professionals Follow-up Study (HPFS, 1990-2023). Participants were free of cancer, cardiovascular disease, diabetes, or neurodegenerative disease at baseline.

Dietary intake was assessed using validated semiquantitative food frequency questionnaires that were administered every 4 years. Butter intake included butter added to food and used in cooking, whereas plant-based oil intake included safflower, soybean, corn, canola, and olive oils.

The primary outcome was total mortality. Secondary outcomes were mortality due to cardiovascular disease (CVD) or cancer. Deaths were identified using the National Death Index and medical records, with causes classified by a physician.

Cox proportional hazards models estimated hazard ratios for mortality, adjusting for potential confounders, including age, BMI, smoking, physical activity, total energy intake, and dietary quality (Alternative Healthy Eating Index). Cumulative average dietary intake was used to minimize measurement error, and substitution models estimated the effect of replacing butter with plant-based oils.

How do the findings compare to those of similar studies?

After 33 years of follow-up, 50,932 participants died, including 12,241 from cancer and 11,240 from CVD. 

Individuals with the highest butter intake had a 15% higher risk of total mortality compared to those with the lowest intake (hazard ratio [HR], 1.15; 95% CI, 1.08-1.22; P for trend < .001). In contrast, those consuming the highest amounts of plant-based oils had a 16% lower total mortality risk (HR, 0.84; 95% CI, 0.79-0.90; P for trend < .001).

Specific plant-based oils, including canola, soybean, and olive oils, were significantly associated with reduced mortality. For every 5 g per day increase in consumption, the risk of total mortality decreased by 15% for canola oil, 8% for olive oil, and 6% for soybean oil. Corn oil, in contrast, showed no significant association between higher intake and reduced mortality risk.

In addition to total mortality risk, higher butter intake was associated with an increased risk of cancer mortality. For each 10 g per day increase in butter consumption, cancer mortality risk went up by 12%. Conversely, each 10 g per day increment in plant-based oil consumption conferred a 11% reduced risk of cancer mortality, plus a 6% reduced risk of cardiovascular disease mortality. 

Replacing 10 g of butter per day with an equivalent amount of plant-based oils was associated with a 17% reduction in both total and cancer mortality.

“Our findings are largely in line with previous evidence linking saturated fats with adverse health outcomes and unsaturated fats with improved lipid profiles and lower inflammation,” Zhang told Medscape Medical News. “However, our study builds on past research by using repeated, long‐term dietary assessments and this approach helps minimize within‐person variability and better reflects real-world dietary habits.”

What potential confounders might have affected the results?

McTiernan noted that the study’s findings may not fully apply to the general population, as the participants were predominantly White healthcare professionals, who may have different dietary habits, financial circumstances, and disease risks than more diverse populations.

She also pointed out that the study focused only on mortality, yet the investigators’ discussion sometimes conflated death risk with disease risk. Multiple factors influence mortality, McTiernan noted, including disease incidence, time until diagnosis, access to preventive care, and treatment availability, all of which are linked to socioeconomic status.

“I really wish that the analyses had looked at risk of the specific diseases: specific and total cardiovascular disease, and specific cancers,” McTiernan said. “That could have given us information on use of specific fats and actual risk of the disease, without the intervening effects, say, of whether someone has the money and time to get specific treatments for their cancer or heart disease.”

What are the clinical implications of this study?

“These results support current dietary recommendations to replace animal fats like butter with nonhydrogenated vegetable oils that are high in unsaturated fats, especially olive, soy, and canola oil,” the investigators write.

McTiernan agreed; she suggested increasing plant oils as part of a plant-based diet, and cooking with vegetable oils to reduce saturated fat intake.

“Read the labels for what’s contained in packed foods,” she added.

What research questions remain unanswered?

Zhang suggested that more work is needed to uncover the molecular mechanisms behind the health benefits and risks of consuming various oils.

She also underscored the need for more research to understand how cooking might alter the health impacts of plant-based oils.

“For example,” she said, “while raw oils (as used in salad dressings) retain their beneficial unsaturated fats, prolonged high‐heat cooking (often used in commercial cooking rather than home-cooking conditions) may oxidize these fats and produce harmful compounds.”

This study was supported by research grants from the National Institutes of Health. Co-author Marta Guasch-Ferré, PhD, reported grants from the Novo Nordisk Foundation and the International Nut and Dried Fruit Council. McTiernan reported no relevant financial relationships.