Seed Oils and Your Health: The Good and the Bad

There’s a new food warning echoing around the internet, but you won’t find it being touted by the World Health Organization (WHO). Or the US Food and Drug Administration. Or the National Institute of Health. This food warning is being sounded on TikTok, Instagram and YouTube.

The message? Seed oils are bad for you. They might even be one of the most harmful foods in the supermarket. At least, that’s according to the online influencers and podcasters.

The problem is this warning isn’t as rooted in reliable science as some of the seed oil naysayers may have you think. The real studies into seed oils – and there have been plenty – tend to come to more positive, if nuanced, conclusions.

Let’s take a look.

Seed oils – The bad

Though linoleic acid is considered to be an essential fatty acid, elevated levels in the blood can be metabolized to form arachidonic acid, a long-chain omega-6 fatty acid that can raise levels of inflammation and coagulation, increasing the risk of cardiovascular disease, particularly atherosclerosis.

Other harmful linoleic acid metabolites include free radicals like hydroxy-eicosatetraenoic acids , which can exacerbate mitochondrial damage, promoting oxidative stress, further contributing to cardiovascular disease.

These risks, however, can be mitigated if seed oils are consumed in recommended moderate amounts.

And yet, globally, it seems people are consuming more seed oils than ever before.

As the oils are increasingly used in the production of ultra-processed foods (UPFs) – from crisps/chips to bread and spreads – most Westerners are now consuming higher volumes of linoleic acid than previous generations.

So, the popular online narrative around seed oils has some understandable origins.

But – and this may be the crucial “but” in countering the growing disinformation around oils – the high levels of linoleic acid found in modern diets are likely still low enough to avoid the cardiovascular disease risks associated with the acid’s metabolites.

Seed oils – The good

Less linoleic acid than you might think

“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, told Technology Networks. “They have cherry picked references that suit their narrative.”

Sanders, unlike many of the online influencers promoting the online “seed oil conspiracy”, has been an active researcher of dietary lipids and how they affect health for the past 50 years.

“I was a member of two WHO/ Food and Agricultural Organization  Expert Consultations (in 1994 and 2008) on the role of fats and fatty acids in human nutrition on which most national dietary guidelines for fat are based,” he said. “I was responsible for the review on the physiological effects of different dietary fatty acids on risk factors in the second consultation. Both consultations recognized that linoleic acid was a dietary essential and that adults needed a minimum about of about four grams a day (two percent dietary energy) to prevent essential fatty acid deficiency.”

Sanders and his colleagues came to a loose agreement on the maximum daily amount of linoleic acid: 10% dietary energy.

“The consultation also recognized that higher intakes had favorable effects on blood cholesterol but were uncertain about the long-term health effects of consuming more than 10% of the energy as linoleic acid because of the possible effect of very high intakes on oxidative stress,” he said.

Fortunately, he says, even with rising levels of linoleic acid in the Western diet, most consumers in the US and UK are still consuming below this 10% threshold.

“The range of intakes from intakes in the UK are currently around fiver 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.”

Benefits of linoleic acid

So, seeing as most of us aren’t consuming a worrying amount of linoleic acid, it’s time to talk more about the health benefits of the fatty acid, according to Sanders. After all, it is an essential fatty acid.

For one thing, the acid’s key concerning metabolite, arachidonic acid, has its cardiac boons when found in lower amounts.

“Arachidonic acid, besides giving rise to pro-inflammatory lipid mediators, also gives rise to mediators that are anti-thrombotic and some anti-inflammatory effects,” said Sanders.

Research has also shown that linoleic acid lowers total and low-density lipoprotein cholesterol – often dubbed the “bad cholesterol” – when compared with saturated fatty acids and carbohydrates.

Large prospective datasets have further shown that relatively higher levels of the acid (5–10% of daily energy) were associated with lower risk of coronary heart disease, stroke and incident Type 2 diabetes mellitus compared with lower levels, suggesting that, across the range of typical dietary intakes, relatively high levels of linoleic acid are beneficial.

Better than butter

So, seed oils clearly have their health benefits as well as their potential health detriments.

But what about other cooking fats? How do seed oils’ benefits and risks stack up against its fatty counterparts?

After all, vocal proponents of the “seed oil conspiracy”, like recently appointed US health secretary Robert F Kennedy Jr., say consumers should instead opt for “traditional” fats such as butter and lard. How do seed oils stand against these solid-at-room temperature animal fats?

Unsurprisingly, very well.

“An important recently published study by the Harvard group (JAMA Internal Medicine) shows that people who chose to eat butter don’t live as long as those who chose to eat vegetable oils,” Sanders told Technology Networks.

After accessing health and dietary data from hundreds of thousands of health professionals, the researchers behind the recent study found that a higher intake of butter was associated with increased mortality, while higher plant-based oils intake was associated with lower mortality.

“It was a well conducted prospective study of 221,054 health professionals who were in their fifties when enrolled and followed up for 33 years,” Sanders expounded. “Dietary intakes were assessed every four 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),” he added.

The reasons behind this difference, say Sanders, are well known: butter is high in saturated fat and low in polyunsaturated fats, whereas soybean and canola oils are low in saturated fatty acids but high in unsaturated fats. 

Saturated fats raise low-density cholesterol (the “bad cholesterol”), which contribute to cardiac disease. Unsaturated and polyunsaturated fats – like omega-6 fatty acids – raise high-density cholesterol (the “good cholesterol”).

So, butter vs canola oil may seem like a valid debate to begin with, but, when one fat is labelled as high in “bad” cholesterol and the other is labelled high in “good” cholesterol, the answer to which is healthier does become more obvious.

And yet the online scaremongering around seed oils continues.

Conclusion

“I think social media and some commentators have seriously mislead the public by suggesting that vegetable seed oils are harmful to health and animal fats are beneficial,” said Sanders.

But how to counter this online misinformation? Perhaps, counterintuitively, by agreeing with part of it. Ultra-processed foods – which often use seed oils as a fat source – are, generally, bad for our health. They tend to be high in saturated fat, salt and sugar, and poor in fiber and essential nutrients – and are now thought to account for 57.9% of the diets of US citizens.

For these reasons, the foods have been blamed for increasing rates of obesity, heart disease and cancer rates in Western countries.

So, perhaps any counter message to the “seed oil conspiracy” should echo the justified concerns around ultra-processed foods that list seed oils as an ingredient while stressing that seed oils themselves, when used as a cooking fat for nutritious meals, are good for our health.

It would take some true dedication for the average person to pass the 10% dietary energy linoleic acid threshold set by experts like Sanders, so – unless you do plan on drowning your breakfast, lunch and dinner in copious pools of sunflower oil every day – don’t feel so nervous next time you consider drizzling a dash in your frying pan.