Seed oils are having a bit of a reputational crisis at the moment.
According to a new online narrative, echoing across sections of social media, the oils are detrimental to human health. Strong links to cancer and cardiovascular disease are often touted. Such sensationalist claims have since been endorsed by the US Health Secretary, Robert F Kennedy Jr., who has advised consumers to instead opt for “traditional” fats such as butter and lard.
But, according to numerous oncologists and cardiologists, this new narrative is just dangerous scaremongering. Animal fats are worse for our cardiac health than vegetable oils, despite the US health secretary’s claims. And linoleic acid, the key omega-6 fatty acid seed oils are rich in, actually has its health benefits.
Indeed, according to new research due to be presented at Nutrition 2025, the annual meeting of the American Society for Nutrition held May 31–June 3, the fatty acid may help to lower risks for heart disease and type 2 diabetes.
What are seed oils?
Seed oils are plant fats extracted from, well, seeds.
There are eight types: canola (rapeseed), corn, cottonseed, grapeseed, soybean, sunflower, safflower and rice bran.
All types contain a high proportion of omega-6 fatty acids, specifically, linoleic acid.
Linoleic acid lowering cardiovascular disease?
“There has been increasing attention on seed oils, with some claiming these oils promote inflammation and raise cardiometabolic risk,” Dr. Kevin C. Maki, an adjunct professor at the Indiana University School of Public Health-Bloomington and chief scientist at Midwest Biomedical Research, said in a statement.
To probe this growing online narrative, Maki and his colleagues performed a cross-sectional analysis of data from 1,894 people in an observational cohort focused on COVID-19.
They found that higher levels of linoleic acid in plasma – indicative of dietary intake – were consistently associated with lower levels of risk factors for cardiovascular disease and type 2 diabetes.
Specifically, participants with higher levels of linoleic acid showed lower levels of glucose, insulin and HOMA-IR – a biomarker of insulin resistance. The participants also had lower levels of inflammation biomarkers, including C-reactive protein, glycoprotein acetyls and serum amyloid A.
“Our study, based on almost 1,900 people, found that higher linoleic acid in blood plasma was associated with lower levels of biomarkers of cardiometabolic risk, including those related to inflammation,” Maki said ahead of presenting his findings at the Nutrition conference.
“We saw consistent results across the different biomarkers measured,” he said. “People with higher levels of linoleic acid in their blood tended to have a healthier overall risk profile for heart disease and diabetes.”
Maki and his colleagues say their findings support the need for additional intervention studies to test whether increasing linoleic acid intake improves cardiometabolic risk factors and lowers the incidence of heart attacks, strokes and type 2 diabetes.
They are next planning to investigate how different types of oils with varying fatty acid content affect cardiometabolic risk factors.
Seed oils and cardiac health
Maki’s study is far from the first to demonstrate linoleic acid’s cardiac benefits.
A clinical trial published back in 1991 found that linoleic acid lowers total and low-density lipoprotein cholesterol – often dubbed the “bad cholesterol” – when compared with saturated fatty acids and carbohydrates.
More recently, a paper published in 2024 used large prospective datasets to demonstrate that relatively higher levels of the acid (5–10% of daily energy) were associated with a lower risk of coronary heart disease, stroke and incident type 2 diabetes compared with lower levels, suggesting that, across the range of typical dietary intakes, relatively high levels of linoleic acid are beneficial.
Nonetheless, the omega-6 fatty acid has become the focal point of online harangues on seed oils, much to the chagrin of cardiac researchers.
“These stories come from people who have no or limited qualifications in the nutritional sciences and who have not generated any data from experimental research,” Dr. Thomas Sanders, a professor of cardiovascular disease risk at King’s College London, recently told Technology Networks. “They have cherry-picked references that suit their narrative.”
Speaking to the publication earlier this year, Professor Sanders explained that only a high intake of seed oils – over 10% of a person’s dietary energy – would pose a substantial risk to human health. Fortunately, he said, even with rising levels of linoleic acid in the Western diet – due to the wide adoption of the oils in ultra-processed foods – most consumers in the US and UK are still only consuming seed oils amounting to 5-7% of dietary energy.
“The range of intakes from intakes in the UK are currently around five percent dietary energy, which is not high,” Sanders said. “Intakes are somewhat higher, six to seven percent, in the USA, but still within the acceptable range.”
“I think social media and some commentators have seriously misled the public by suggesting that vegetable seed oils are harmful to health and animal fats are beneficial,” he added.
Reference: Maki KC, Wilcox ML, Kirkpatrick CF, et al. Associations of serum omega-6 polyunsaturated fatty acids with biomarkers of glucose homeostasis. Curr Develp Nutri. 2025. doi: 10.1016/j.cdnut.2025.106488
*This article is based on research findings that are yet to be peer-reviewed. Results are therefore regarded as preliminary and should be interpreted as such. Find out about the role of the peer review process in research here. For further information, please contact the cited source.