A debate is raging in the nutrition world: are seed oils or saturated fats to blame for heart disease?
The leading cause of death in the U.S., one in five fatalities in 2022 was attributed to heart disease, according to the Centers for Disease Control and Prevention (CDC).
But nutrition experts are split about what causes it. Some say that saturated fats are to blame, and that is the conventional view.
Saturated fats are solid at room temperature. Food sources include cheese, egg yolks, red meat and butter, and for years they have been associated with a higher risk of heart problems, including cardiovascular disease, coronary artery disease, heart attacks and stroke.
However, recently some experts have been accusing seed oils of being the real culprit, as they contribute to chronic inflammation in the body. Seed oils—such as sunflower oil, canola oil and grape seed oil—are refined oils commonly used to fry foods at high temperatures, and they are found in highly processed foods, such as commercially produced baked goods and snacks.
Bridget Benelam is a nutritionist who takes the view that saturated fat contributes towards heart disease and should be avoided.
She told Newsweek: "Research shows that reducing saturated fat in the diet and replacing it with unsaturated fats improves blood lipid profiles—such as lowering LDL ('bad') cholesterol—and reduces the risk of cardiovascular disease (heart disease and stroke) and coronary artery events, like a heart attack."
LDL cholesterol—in full, low-density lipoprotein cholesterol—is known as "bad" cholesterol, as high levels in the blood are associated with risk factors for heart disease.
"In practice, this means reducing consumption of foods like fatty and processed meats, cakes, biscuits and pastries, butter, cream and coconut oils, and, instead of these, getting fat from unsaturated sources such as rapeseed, olive or sunflower oils and foods such as nuts, seeds and oily fish," said Benelam.
Nichola Ludlam-Raine is a dietician who agrees. She told Newsweek: "When comparing seed oils and saturated fats in terms of health, saturated fats are generally considered more harmful and are less preferred, particularly for cardiovascular health.
"Higher intakes of saturated fats—found in foods such as butter, cheese, red meat, and processed snacks—have been consistently associated with higher LDL cholesterol levels, which is a significant risk factor for heart disease.
"In contrast, seed oils like sunflower, rapeseed and soya bean oils, are rich in polyunsaturated fats (especially omega-6 fatty acids) and tend to be associated with improved cardiovascular outcomes when used in place of saturated fats."
Ludlam-Raine said that saturated fats contribute to heart disease by raising LDL cholesterol levels, which can accumulate in the arteries and lead to the formation of plaque, which can stiffen and harden—known as atherosclerosis—and increase the risk of heart attacks and strokes.
It's an explanation that many may recognize—but one that some nutritionists are challenging. Mike Murphy is one of them.
When Newsweek reached out for comment, Murphy recommended a podcast episode in which he articulated his views on the subject in February 2024.
"We used to think that [heart disease] was mostly about too much saturated fat and cholesterol in the diet, because plaque is a fatty, waxy substance that incidentally is made from cholesterol," he said on The Nutrable Podcast, in an episode titled "The Truth About Cholesterol."
Murphy said that foods that rich in cholesterol were previously believed to clog blood vessels, "like a sewer pipe gets clogged if you pour too much grease down the drain."
"But it turns out we got that one wrong, and that myth was disproven a long time ago, but sadly, not enough people got the memo, and so there's still this belief that fat and cholesterol are public enemy number one when it comes to heart health," he said on the podcast.
But the "villain" isn't fat, he said, it's inflammation. Inflammation is a crucial part of the body's immune system that responds to infection and injury to help the body heal and recover.
However, if inflammation doesn't die down in the body when it's no longer needed, it can cause problems, increasing the risk of diseases such as obesity, type 2 diabetes and heart disease, or worsening the symptoms of chronic conditions such as arthritis.
Murphy explained how he believed inflammation could cause heart disease on the podcast.
"If you've got inflammatory molecules circulating throughout the bloodstream, day in and day out, even just low-grade inflammation, the blood vessels get irritated...and they have to adapt to protect themselves from this constant heat," he said.
He explained that the body reacted by bringing in cholesterol, which could start to build up and form a plaque on the lining of the blood vessels.
"If that inflammation continues, that plaque builds up, in an effort to protect that vessel from damage or potential rupture," he said. This, he said, was atherosclerosis—that cholesterol buildup that could harden and become stiff, leading to heart disease.
"Yes, cholesterol is involved, but it doesn't initiate the process," he said. "Blaming cholesterol for atherosclerosis is like blaming the fire department just because we found them at the scene of the fire."
Rather than saturated fats, then, nutritionists like Murphy assert that inflammation is the cause of heart disease—not saturated fat—and foods which are considered inflammatory include high-sugar foods, ultra-processed foods (i.e. commercial products made with industrially refined ingredients) and seed oils.
Seed oils are considered inflammatory partially because they are high in omega-6. Omega-6 is a fatty acid that competes in the body with fatty acid omega-3, which is generally believed to be anti-inflammatory, good for brain health, and a nutrient that promotes longevity.
The Western diet is thought by many nutrition experts to be too high in omega-6 and not high enough in omega-3, leading to higher levels of inflammation in the body.
However, Ludlam-Raine disputed that inflammation caused by omega-6 in seed oils would contribute towards heart disease more than saturated fats.
She said: "While omega-6 fatty acids are occasionally criticized for potentially promoting inflammation, the majority of research suggests that substituting saturated fats with polyunsaturated fats from seed oils actually reduces cardiovascular risk.
"Seed oils, when consumed in moderation as part of a balanced diet, are generally heart-healthy due to their cholesterol-lowering effects.
"Concerns about inflammation and metabolic disorders linked to omega-6 fatty acids from seed oils are largely unsubstantiated in the context of typical dietary patterns."
Ludlam-Raine recommended getting a balanced fat intake from a variety of sources and focusing on overall dietary quality.
Benelam advised avoiding sources of saturated fat and swapping them for sources of unsaturated fat, such as rapeseed, olive or sunflower oils, and foods such as nuts, seeds and oily fish.
Murphy said ultra-processed foods were to be avoided, and a Mediterranean eating pattern—that prioritizes fresh whole foods (i.e. unprocessed) and uses olive oil as its primary fat—was a beneficial eating pattern to follow.
Do you have a tip on a food story that Newsweek should be covering? Is there a nutrition concern that's worrying you? Let us know via science@newsweek.com. We can ask experts for advice, and your story could be featured in Newsweek.
Disclaimer: The copyright of this article belongs to the original author. Reposting this article is solely for the purpose of information dissemination and does not constitute any investment advice. If there is any infringement, please contact us immediately. We will make corrections or deletions as necessary. Thank you.
