Seed oils have been getting a bad rap in recent years, with many people claiming they’re ruinous for our health.
It’s become commonly believed that they significantly increase heart disease, diabetes and general inflammation risk.
But which seed oils are lumped in with this claim, and should we really be concerned about them?
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The so-called ‘hateful eight’ are as follows:
- Canola
- Corn
- Cottonseed
- Grapeseed
- Soy
- Rice bran
- Sunflower
- Safflower
Each of these contains a high level of omega-6 fatty acid, which provide essential nutrition but cannot be produced in the human body.
Some studies have linked omega-6 fatty acids with chronic inflammation which can in turn increase the risk of various cancers and heart disease.
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Much of the sentiment around omega-6 fatty acids being terrible for our health are rooted in observational studies where participants self-report what they consume. Data from such studies isn’t hugely reliable as people can make mistakes, misremember, or even lie about what they’re consuming.
Several controlled trials have found that they in fact don’t increase inflammation. Professor Dariush Mozaffarian, director of the Food is Medicine Institute at Tufts University in Massachusetts, told the BBC: "New research shows that omega-6 fatty acids give rise to unique natural molecules, like lipoxins, that have powerful anti-inflammatory effects in the body.”
Recently-published research that examined 200,000 people’s diet and health in the US across a 30-year span found that those who consumed more plant oils were in fact less likely to die from cardiovascular illness or cancer.
However, those who consumed higher levels of butter had an increased mortality rate over those 30 years.
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In other studies assessing omega-6 fatty acids’ impacts on our health, the focus has been on linoleic acid. This is an omega-6 fatty acid that’s particularly concentrated in seed oils, and it’s been found to lower LDL cholesterol in our blood.
In fact, a 2019 study found that participants with higher levels of linoleic acid in their diets were 7% less likely to die from heart disease.
"Linoleic [acid] might improve cholesterol to reduce the risk of cardiovascular disease, and also improve glucose metabolism, which reduces the risk of type 2 diabetes," Matti Marklund, assistant professor of human nutrition at Johns Hopkins Bloomberg School of Public Health, told the BBC.
Finally, some have claimed that an imbalance of omega-6 fatty acids against omega-3 is bad for our health, with seed oils having high levels of omega-6.
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Data shows that 15% of Western diets’ energy intake is covered by omega-6 fatty acids, and the average person’s omega-3 to omega-6 consumption ratio can be as high as 50:1. Studies show that a ratio of 4:1 is better for cutting cardiovascular health, implying we should we consuming more omega-6 on average.
That said, a 2022 investigation by the World Health Organisation found that a higher intake of omega-6 against omega-3 posed an increased risk of cognitive decline and chronic inflammatory bowel disease.
Those with a higher ratio of omega-3 to omega-6 meanwhile had a 26% reduced risk of depression.
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The WHO report concluded that high consumption of omega-6 from seed oils wasn’t likely to increase the risk of mortality or chronic disease, although it was caveated with the fact more studies are required for conclusiveness.
In sum, the answer to omega-6 fatty acids isn’t necessarily to reduce your intake of them, but to increase your omega-3 consumption instead.
Rachael Davis