Are seed oils toxic and unsafe?

By December 15, 2022 Health, Lifestyle

We came across the following post on the blog page of the website The article was reposted on the social media site Reddit in on 6 December:

The article focuses on the health risks of seed oils high in linoleic acid—a polyunsaturated omega-6 fatty acid. These are listed as canola (rapeseed) oil, corn oil, cottonseed oil, grapeseed oil, peanut oil, rice bran oil, safflower oil, soybean oil and sunflower oil. These oils make up most of what are commonly known as vegetable oils.

Toxic Allegations

The article suggests that linoleic acid is a highly harmful substance, and the high linoleic acid content of these seed oils makes them both toxic and unsafe for consumption.

Multiple health risks of linoleic acid are implied throughout the article, including inflammation, immunologically harmful effects, heart disease, diabetes, lower fertility, Alzheimer’s disease, obesity, cancer, and early death.

The author claims that despite these risks, the consumption of seed oils is widespread because they were invented when ‘there was no meaningful health regulation’ and became popular ‘based on flawed research suggesting they were heart healthy’.

To support the claims of the health risks of seed oils, an extensive host of medical studies are cited in the article. However, a closer look at the studies cited reveals a lack of consistent evidence supporting the article’s claims of health risks of linoleic acid, as well as gaps in the logic of the author. The author also relies on findings from in-vitro (cell) and in-vivo (animal) studies, which cannot always be translated to be relevant for humans.

In some instances, the author of the article appears to rely on data from studies several decades old while at the same time neglecting key details. For example, in a section where he posits that linoleic acid results in higher incidence of cancer-related death, a study published in 1971 is cited. The article claims the study shows that participants eating more calories from linoleic acid were 82% more likely to die from cancer. A glance at the abstract, however, shows that while the figure is accurate, the result indicates a p-value of 0.06, which is not considered statistically significant in most studies.

***The p-value measures the probability of obtaining the observed results if there is no difference between the two sets of data being analysed. A p-value of 0.06, therefore, means that there is a 6% chance that the observer would arrive at the results even if there was no difference in the two groups of people.***

In another section, the article claims that researchers found that high levels of oxidised low-density-lipoprotein (ox-LDL), a particle in cholesterol that is a marker for heart disease, was ‘most likely due to its linoleic acid content’. This statement is absent from the report of the study, which did not designate linoleic acid as the primary substance responsible. The authors also note weaknesses in the study design such as lack of information about participants’ nutrition lifestyle and small sample size, which would necessitate further research.

Experts Cut the Fat

To assess the validity of the article’s claims, we investigated the findings of other studies on the issue. In doing so, we found that far from there being a consensus on the issue, recent studies had found results that directly contradicted the article’s claims; linoleic acid was associated with anti-inflammatory effects and reduced rates of cardiovascular disease.

Due to the highly technical nature of these medical studies, the view of experts in the field can be helpful in interpreting the results. In a recent article on Consumer Reports, Dariush Mozaffarian, a cardiologist and professor of nutrition at Tufts University, says that the evidence against seed oils in the available research is ‘incorrect or incomplete’.

Guy Crosby, adjunct associate professor of nutrition at the Harvard School of Public Health, also addresses in the same article the claims that the processing of seed oils results in toxic byproducts. He indicates that only trace amounts are found in seed oils, and since they are only heated for short periods, they have fewer unhealthy trans fats than animal fats like butter.

Crosby suggests that the true hazard lies in repeatedly reheating seed oils containing unsaturated fats to high temperatures—an unlikely scenario in home cooking—which causes a buildup of damaging chemicals. He also adds that inexpensive seed oils are often used in packaged, processed and fried foods, and those who attribute their improved health after cutting back on seed oils may instead be benefiting from reducing their intake of processed foods.

Dubious Claims of Seedy Origins

A glance into the past reveals that the accusations of seed oils being toxic have been around for years. In 2013, the Australian media network ABC published an interview in which three experts debunked claims about seed oils in a book by David Gillespie that were identical to those being made on the Zero Acres site. These claims appear to have resurfaced across social media platforms in 2021 after Joe Rogan interviewed the seed oil-sceptic doctor Paul Saladino about the issue on his podcast show. Jeff Nobbs, the CEO of Zero Acre, recently joined Paul Saladino on the latter’s podcast to talk about ‘how seed oils make you fat’. He has also made multiple blogposts and appearances on podcasts denouncing vegetable oil in the last two years.

Browsing through the Zero Acre website, it becomes evident that Jeff Nobbs and his company may not be the most reliable source for information on vegetable oil. Zero Acre sells what they brand ‘cultured oil’, oil produced from introducing microorganisms into sugar to induce fermentation.  Each 473ml bottle costs 29.99 USD—a cost far greater than most vegetable oils, and one of its key selling points is that it is low in linoleic acid.

The article on Zero Acre appears to cherry-pick evidence to support its arguments on the effects of linoleic acid, but it appears that the relative benefits of seed oils high in linoleic acid/polyunsaturated fats in comparison to their alternatives continues to be a matter of contention in the scientific community, and many experts instead emphasise their benefits.

There is no evidence to corroborate the logical leap made in the Zero Acre article that seed oils are toxic and unsafe for consumption. Furthermore, Zero Acre’s sale of a competing product makes it an unreliable source for a conclusive reading of the issue.

As such, it is false that seed oils are toxic and unsafe.

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