March 6, 2025
Scientists comment on a study published in JAMA Internal Medicine looking at butter consumption, plant-based oil consumption, and all-cause, cancer-related and cardiovascular disease-related mortality.
Prof Sarah Berry, Professor of Nutritional Sciences, King’s College London, said:
“The study shows that high butter consumption is linked to increased cancer and total mortality, whereas plant-based oils are linked to a lower risk of overall mortality and death due to cardiovascular disease and cancer.
“This research is very timely. Social media is currently awash with influencers promoting butter as a health food and claiming that seed oils are deadly. This large-scale, long-term study finds the reverse. The authors produce further evidence that seed oil consumption is linked to improved health and that butter – delicious as it is – should only be consumed once in a while.
“In a sane world, this study would give the butter bros and anti-seed oil brigade pause for thought, but I’m confident that their brand of nutri-nonsense will continue unabated.”
Dr Louise Flanagan, Head of Research for the Stroke Association, said:
“Stroke is the fourth leading cause of death in the UK and a leading cause of adult disability – but, fortunately, nine out of 10 strokes can be prevented. High blood pressure is the cause of around half of all strokes.
“This study covered a wider range of plant oils than previous research to find that greater consumption of rapeseed oil, soybean oil or olive oil is associated with an overall lower risk of death. It is positive to see other plant oils being considered in this way as olive oil has been a focus of much research in the past.
“The suggestion to switch from butter to plant oils is achievable for many people. However, it was only olive oil that was associated with a lower risk of death due to cardiovascular disease, including stroke. Olive oil is typically more expensive than other oils like rapeseed which means that its potential health benefits could be out of financial reach for some.
“The study didn’t consider what eating both butter and plant oils means in terms of health risks, which is likely to be what many people naturally do. This is potentially something which could be considered in future studies.
“The Stroke Association encourages people to maintain a healthy diet, exercise regularly, not smoke and monitor alcohol intake, which can help to maintain healthy blood pressure. Anyone with concerns should speak to their GP.”
Prof Parveen Yaqoob, professor of nutritional science at the University of Reading, said:
“The link between diets high in saturated fat, particularly animal-based fat such as butter and lard, and higher mortality has been argued for decades. I have seen American adverts from the 1960s extolling the virtues of American housewives “polyunsaturating” their husbands when they come home from work. This is a fun historical reminder of the link between the food industry and dietary health messages, as well as showing how much woman have had to fight for social progress.
“This latest research provides strong additional data to support the ‘healthier fats’ theory. The research followed a large cohort of health workers in America over many years. The use of food frequency questionnaires means that we are relying on the participants to remember what they have eaten and how much, which we know can be an unreliable indicator of actual dietary patterns.
“The scientists for this study highlight that not all vegetable oils are equal. Although butter was being replaced by corn oil and sunflower oil, which are polyunsaturated, in the 1960s and 70s, the oils they are talking about in the research – olive, canola and soybean – are mainly monounsaturated. The researchers suggests that these are more beneficial than the polyunsaturated fats, and refer to the Mediterranean diet, which is higher in monounsaturated fats such as olive oil, for that reason. While many Western diets shifted away from saturated fat to polyunsaturated fat in the 1970s, the oils that we consume more often now contain more monounsaturates, which seem to be more beneficial. Given that there are some plant-based oils that are high in saturates – such as palm oil and coconut oil – it is important to consider them separately.
“Recent dietary fads have suggested a re-examination of evidence on dietary fat. People who are confused about these conflicting messages about their diet should focus on broader, well-established advice, which can be summarised as: eat more fresh vegetables.”
Prof Tom Sanders, Professor emeritus of Nutrition and Dietetics, King’s College London, said:
“This important study shows that people who chose to eat butter don’t live as long as those who chose to eat vegetable oils. It is a well conducted prospective study of 221,054 health professionals who were in their fifties when enrolled and followed up for 33 years. Dietary intakes were assessed every 4 years. The study reports that those who had the highest intake of butter were 15% more likely to die prematurely (from both cardiovascular disease and cancer). In comparison the opposite was true (a 16 % reduction in relative risk of all-cause mortality), for participants who had the highest intake of vegetable oil. The same relationship was seen for olive oil, soybean oil and canola oil (rapeseed oil).
“The strength of the study is the long period of follow-up, repeated measures of dietary intake and adjustment in the statistical analysis for other factors such as smoking habit and obesity. The findings do not apply to sunflower, palm or coconut oils which were not consumed to any significant extent in this study. The limitations are that this an observational study not a randomised controlled trial. Furthermore, the findings with regard to health professionals may differ from the general population because they are better informed about healthy lifestyle choices.
“Butter is high in saturated fat, contains some trans fatty acids but is very low in polyunsaturated fats. Whereas unhydrogenated soybean, canola and olive oils are low in saturated fatty acids but high in unsaturated fats. Replacement of butter with these vegetable oils is well documented to lower blood cholesterol, particularly that associated with low density lipoprotein (LDL) by about 10%. This change in LDL cholesterol would be predicted to reduce the relative risk of death by about 3% which is much less than what was observed in this study. It remains possible that a higher intake of polyunsaturated fatty acids (especially linoleic acid) from the vegetable oil may have played a role in reducing risk by a variety of mechanisms. An alternative explanation may be that health professionals who are sensible follow prevailing healthy eating and lifestyle advice compared to those who don’t.
“The take home message is that it is healthier to choose unsaturated vegetable oils rather than butter. This is particularly relevant as there has been much negative publicity about vegetable oils on social media, which are based on unfounded claims of potential harmful effects, rather than deaths as described in the present study.”
Prof George Davey Smith, FRS FMedSci, Professor of Clinical Epidemiology, University of Bristol, said:
“Yet again these studies show that the exposure that is accompanied by large differences in other adverse health exposures – e.g. more than double the rate of cigarette smoking in the highest quartile vs lowest quartile of butter consumption is associated with worse health outcomes. That these differences cannot be taken into account by the statistical models the authors use is well known; measurement error and unmeasured factors ensure this. It is now more than 30 years since these authors published two high profile papers back to back in the New England Journal of Medicine claiming that vitamin E supplement use would reduce heart disease risk by 40%. The claims were incorrect, but many people believed them – the story was the headline news in the New York Times – and started taking vitamin E supplements. However randomised trials later showed this was nonsense: there was no benefit. This is documented in the first few minutes of this recent talk https://www.youtube.com/watch?v=8IgpTT5ZXXU&t=2s As in the conclusion of my blog1 on the same authors’ “dark chocolate” paper, the interesting question this paper raises is “why do supposedly legitimate journals keep publishing papers like this?”.”
1https://ieureka.blogs.bristol.ac.uk/2024/12/04/dark-chocolate-diabetes/
* ‘Butter and Plant-Based Oils Intake and Mortality’ by Yu Zhang et al. will be published in JAMA Internal Medicine at 21:00 UK time on Thursday 6 March 2025, which is when the embargo will lift.
DOI: 10.1001/jamainternmed.2025.0205
Declared interests
Prof Sarah Berry: “Sarah has received funding from the Almond Board of California, Malaysian Palm Oil Board and ZOE (Chief scientist at ZOE Ltd, options and consultancy at ZOE Ltd.).”
Dr Louise Flanagan: “None.”
Prof Parveen Yaqoob: “Professor Parveen Yaqoob is Deputy Vice-Chancellor, and Pro-Vice-Chancellor (Research & Innovation) of the University of Reading, and professor of nutritional science in the Department of Food and Nutritional Sciences, which has funding from public bodies, charities and businesses to conduct independent scientific research on food and nutrition.
The Department has done work on dietary fat, including research co-authored by Parveen as part of the DIVAS project: https://research.reading.ac.uk/ifnh/cases/milk-dairy-consumption-risk-cardiovascular-diseases-cause-mortality/ Mostly government or UKRI funded, with industry partners. The papers listed from that project list grant numbers.
Work on reducing saturated fat in dairy was a REF case study, which includes grant numbers from BBSRC and MRC, and had industry partners throughout, which is one of the ways in which the research was considered to have impact.
https://results2021.ref.ac.uk/impact/eefa0a3d-4ba8-4419-8c28-836e06b41eed?page=1.”
Prof Tom Sanders: “I am a member of the Programme Advisory Committee of the Malaysia Palm Oil Board which involves the review of research projects proposed by the Malaysia government.
I also used to be a member of the Scientific Advisory Committee of the Global Dairy Platform up until 2015.
I did do some consultancy work on GRAS affirmation of high oleic palm oil for Archer Daniel Midland more than ten years ago.
My research group received oils and fats free of charge from Unilever and Archer Daniel Midland for our Food Standards Agency Research.
Tom was a member of the FAO/WHO Joint Expert Committee that recommended that trans fatty acids be removed from the human food chain.
Member of the Science Committee British Nutrition Foundation. Honorary Nutritional Director HEART UK.
Before my retirement from King’s College London in 2014, I acted as a consultant to many companies and organisations involved in the manufacture of what are now designated ultraprocessed foods.
I used to be a consultant to the Breakfast Cereals Advisory Board of the Food and Drink Federation.
I used to be a consultant for aspartame more than a decade ago.
When I was doing research at King’ College London, the following applied: Tom does not hold any grants or have any consultancies with companies involved in the production or marketing of sugar-sweetened drinks. In reference to previous funding to Tom’s institution: £4.5 million was donated to King’s College London by Tate & Lyle in 2006; this funding finished in 2011. This money was given to the College and was in recognition of the discovery of the artificial sweetener sucralose by Prof Hough at the Queen Elizabeth College (QEC), which merged with King’s College London. The Tate & Lyle grant paid for the Clinical Research Centre at St Thomas’ that is run by the Guy’s & St Thomas’ Trust, it was not used to fund research on sugar. Tate & Lyle sold their sugar interests to American Sugar so the brand Tate & Lyle still exists but it is no longer linked to the company Tate & Lyle PLC, which gave the money to King’s College London in 2006.”
Prof George Davey Smith: “No COIs.”