skepticalraptor.com

Plant-based oils in diet are linked to a lower mortality risk

HHS Secretary Robert F Kennedy Jr has been bashing plant-based oils, especially seed oils, claiming that they fuel inflammation and high rates of chronic diseases like obesity and diabetes. Seed oils, a description pushed by internet influencers, wellness gurus, and some politicians like Kennedy, refer to common cooking oils such as canola, soybean, and corn oil.

However, a new large longevity study suggests that more butter is bad, more plant oils are good — and substituting plant-based oils for butter translated into better survival over several decades.

Kennedy and other pseudoscience-pushing nutrition advocates have said Americans are being “unknowingly poisoned” by seed oils. Kennedy has called for fast-food restaurants to return to using beef tallow (rendered animal fat) in their fryers.

Of course, it’s not surprising that RFK Jr is wrong about a health, science, or medicine topic. He probably won’t read this new study which provides solid evidence that plant-based oils have positive health benefits.

As I usually do, I will review this new research and try to explain what it says about plant-based oils and butter.

person slicing butter with a knife plant-based oils

Photo by Felicity Tai on Pexels.com

Plant-based oils research

In a paper published on 6 March 2025 in JAMA Internal Medicine, Dong Wang, MD, ScD, of Brigham and Women’s Hospital and Harvard Medical School in Boston, and colleagues, developed a prospective population-based cohort study that included over 220,000 adults who were free of cancer, cardiovascular disease, diabetes, or neurodegenerative disease at baseline from three large databases:

Nurses’ Health Study (all women, mean age of 56.1)

Nurses’ Health Study II (all women, mean age of 36.1)

Health Professionals Follow-up Study (all men, mean age of 56.3)

Eating habits logged in these studies were linked to U.S. mortality data that were taken from nationwide records and assigned causes based on death certificates and medical records. There were 50,932 deaths identified for the study, including 12,241 from cancer and 11,240 from cardiovascular.

Participants answered semi-quantitative food frequency questionnaires every four years. They reported the frequency and quantity of specific foods, types of fats and oils, and the brands or types of oils used for cooking and added at the table over the preceding year.

Here are the key results:

After 33 years of follow-up, the highest quartile of butter consumption had a 15% higher mortality risk than the lowest quartile.

The highest quartile of plant-based oils consumption had a 16% lower mortality risk compared to the lowest quartile which made it appear that those oils had a protective effect.

Substituting 10g of butter intake per day with an equivalent amount of plant-based oils reduced mortality risk by 17%. It also reduced the risk of cancer death by 17%. However, there was no change in mortality from cardiovascular disease.

The mortality risk was decreased by 15% for every 5g increase in daily intake of canola oil, 6% for soybean oil, and 8% for olive oil. Corn and safflower oil did not exhibit these trends.

Every 10g daily increase in plant-based oils consumption was associated with a 11% reduction in risk of cancer mortality and 6% reduction in cardiovascular disease mortality.

Every 5g increase in daily butter consumption increased mortality risk by 4%.

Every 10g increase in daily butter consumption increased cancer mortality by 12%

Palm and coconut oil were not included in this study.

The researchers concluded:

The present findings are closely aligned with the dietary recommendations of the American Heart Association and the Dietary Guidelines for Americans, which advocate for reducing saturated fat intake and replacing it with polyunsaturated and monounsaturated fats to lower the risk of chronic disease. The present results indicate that replacing three 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.

a bottle of wine standing next to a cutting board with snacks

Photo by Rahime Gül on Pexels.com

Summary

As I usually write with these types of studies, there is a strong possibility of memory bias since dietary oil consumption requires logging information into a diary. Furthermore, the study lacked a consideration of individual socioeconomic status, which may have variations that could affect dietary choices and health outcomes. These are confounding variables that could significantly change the quality of the results.

That being said, there may be good reasons to find these links between plant-based oils and mortality to be closely related.

Butter, and other animal fats (think tallow) have higher saturated fat and cholesterol alongside lower levels of beneficial nutrients making it less suitable for long-term health. On the other hand, plant-based oils are enriched with unsaturated fatty acids (including omega-3 fatty acids) and bioactive compounds. They may provide anti-oxidative and anti-inflammatory properties that may protect against chronic diseases and premature mortality.

One important result of this study is that less expensive oils, such as soybean and canola oil, have nearly the same benefits as olive oil, which is often much more expensive. Of course, this study did not account for the flavor of plant- and animal-based oils.

This study shows the health value of various plant-based oils that humans consume. It clearly shows that they are healthier and reduce the risk of premature death. That’s good enough for me.

Citations

Zhang Y, Chadaideh KS, Li Y, Li Y, Gu X, Liu Y, Guasch-Ferré M, Rimm EB, Hu FB, Willett WC, Stampfer MJ, Wang DD. Butter and Plant-Based Oils Intake and Mortality. JAMA Intern Med. 2025 Mar 6:e250205. doi: 10.1001/jamainternmed.2025.0205. Epub ahead of print. PMID: 40048719; PMCID: PMC11886867.

Michael Simpson

Lifetime lover of science, especially biomedical research. Spent years in academics, business development, research, and traveling the world shilling for Big Pharma. I love sports, mostly college basketball and football, hockey, and baseball. I enjoy great food and intelligent conversation. And a delicious morning coffee!