By EMILY JOSHU STERNE HEALTH REPORTER FOR DAILYMAIL.COM
Published: 12:47 EST, 7 March 2025 | Updated: 12:53 EST, 7 March 2025
Swapping butter for cooking oils may help you live longer, a study found, flouting claims made by Robert F Kennedy Jr that seed oils are linked to chronic diseases.
Eating large amounts of butter has long been linked to high cholesterol and harmful inflammation, which can fuel chronic diseases like diabetes and heart disease.
Seed oils were frequently suggested for use in place of butter, but they've come under fire recently as newly selected health secretary RFK Jr said Americans are being 'unknowingly poisoned' by seed oils and called for fast food restaurants to use beef tallow, or animal fat, instead.
And in his Senate confirmation hearing Thursday, FDA commissioner nominee Dr Marty Makary called for a closer review of seed oils, calling them 'a good example of where we could benefit from a consolidation of the scientific evidence.'
But now, a 30-year study of more than 200,000 adults found people who choose to cook with plant oils - which include olive, avocado, sunflower, canola, corn, and grapeseed - over butter were less likely to die of any cause, including cancer and heart disease.
Meanwhile, people who used butter had a higher risk of dying from cancer or any cause.
Harvard University researchers were 'surprised' to find swapping less than a tablespoon of butter for the same amount of oil lowered the overall risk of death by 17 percent, which the team called 'a pretty huge effect on health.'
Researchers suggested this could be because seed oils are lower than butter in saturated fat, which has been linked to an increased risk of heart attack, stroke, and some forms of cancer.
An NIH-funded study from Harvard University found that replacing butter with seed oils may lower the overall risk of death, especially from cancer and heart disease
Health secretary Robert F Kennedy Jr, pictured here, has slammed seed oils and claimed Americans are 'unknowingly being poisoned' by them
Study author Dr Daniel Wang, assistant professor in the Department of Nutrition at the Harvard TH Chan School of Public Health, said: 'People might want to consider that a simple dietary swap — replacing butter with soybean or olive oil — can lead to significant long-term health benefits.
'From a public health perspective, this is a substantial number of deaths from cancer or from other chronic diseases that could be prevented.'
Cardiovascular disease and cancer are America's two biggest killers, taking 900,000 and 600,000 lives every year, respectively.
The average American consumes almost 100 pounds of seed oils per year, according to some estimates, which is up about 1,000-fold compared to the 1950s. Seed oils became popular in the United States after WW2 thanks to agricultural advances.
Meanwhile, the latest data from the US Department of Agriculture (USDA) found most Americans ate 6.5 pounds of butter in 2023, which could signal a growing movement away from butter and toward seed oils.
The new study, published this week in JAMA Internal Medicine and partly funded by the National Institutes of Health (NIH), analyzed health data from 211,054 workers from the US databases Nurses' Health Study (NHS), Nurses’ Health Study II, and Health Professionals Follow-Up Study (HPFS).
The average participant age for each cohort was 56, 36, and 56, respectively.
Every four years over a 30-year study period, participants completed surveys about their diet and exercise habits.
Dr Marty Makary, pictured here has been tapped to lead one of America's largest health agencies, the FDA. In his confirmation hearing this week, he called for closer reviews of seed oils
Those who had a higher intake of butter were more likely to have a higher body mass index (BMI) and calorie intake, and they were less physically active and less likely to take vitamins.
The researchers then estimated how often participants consumed butter and seed oils, including butter and margarine blends, spreadable butter, butter used in baking and frying, and oils used in frying, sautéing, baking, and in salad dressings.
Over 33 years, 50,932 deaths were recorded, with the most common causes being heart disease and cancer.
Researchers found participants who ate the most butter had a 15 percent higher risk of dying from any cause than those who ate the least.
Additionally, participants who ate the most plant-based oils had a 16 percent lower risk of death than those who ate the least.
The researchers also found substituting 10 grams of butter per day (0.35 ounces, or less than one tablespoon) with the same amount of plant-based oils lowered the risk of death by 17 percent.
Dr Wang said: 'Even cutting back butter a little and incorporating more plant-based oils into your daily diet can have meaningful long-term health impacts.'
Along with the new administration's health leaders, influencers have also slammed seed oils as 'toxic.'
Despite claims from health officials like RFK Jr, the American Heart Association and American Cancer Society have said there is no evidence moderate amounts of seed oils cause chronic conditions or increase the risk of death.
And the American Heart Association also suggests there is no evidence that seed oils in moderate amounts cause inflammation.
The agency said earlier this year there is 'no reason to avoid seed oils and plenty of reasons to eat them,' as they could lower cholesterol and the risk of heart disease and stroke.
But experts stress everything in moderation is important.
In large amounts, the omega-6 fatty acids in plant oils like safflower and sunflower oil can convert into molecules called prostaglandins, which can lead to inflammation.
Dr Yu Zhang, lead study author and researcher at Harvard-affiliated Brigham and Women's Hospital, told CNN olive, canola, and soybean oils are the healthiest choices of plant-based oils due to their high omega-3 fatty acid levels.
Omega-3s have been shown to reduce inflammation and lower the amount of lipids called triglycerides in the blood. Triglycerides can cause plaque to build up in the arteries, making it harder for blood to flow to the heart, increasing the risk of heart disease.
Some studies have also suggested omega-3s can slow tumor growth in cancer patients.
The study's main limitation was showing associations rather than causations, so it's unclear if butter or seed oils directly cause a change in death rates.
Additionally, the team also only looked at health professionals, so more research may be needed on a more diverse population.