What once were ingredients that went under the radar, seed oils have become the central target of the US nutrition war. White House official Robert F. Kennedy Jr., the current Secretary of Health and Human Services and longtime critic of food processing, has even claimed they are “poisoning” Americans.
Being from France, a country that is health conscious and that takes proactive measures like banning toxic food ingredients, I’ve become more aware of healthy eating. In my own life, this awareness has had a real, positive impact on my well-being. However, I’ve had mixed feelings watching the healthy-eating movement grow in the US. While I am very happy that people are increasingly paying attention to what they are consuming, misinformation and oversimplifications make it hard to know what to actually look out for. That is why I am writing this column: as an effort to help people focus on the facts and not blindly follow trends.
Before today’s seed oils became the main antagonist, the public enemy was partially hydrogenated oils (PHOs). They are made through a chemical process called hydrogenation, where hydrogen is added to oils with unsaturated fats (like seed oils). The fats then become more saturated. Hence they become more solid, they have a longer shelf life, and are more stable at high temperatures. These aforementioned qualities gave PHOs practical advantages for food manufacturers. However, when oils are partially hydrogenated, some of the unsaturated fats flip configuration and turn into artificial trans fat: a type of extremely unhealthy fat that worsens cholesterol levels and increases the risk of heart disease. Fully hydrogenated oils, not to be confused with partially hydrogenated ones, are not banned and don’t contain artificial trans fat, but are high in saturated fat.
Luckily, PHOs were banned by the FDA in 2015 and phased out by 2018. A 2012 CDC study on packaged food found that “up to two thirds of ‘seasoned processed potatoes’ contained partially hydrogenated oils.” When PHOs were phased out by the FDA, food manufacturers needed to find replacements. As a result, unhydrogenated seed oils, which the controversy is centered around today, are widely used.
“Seed oil” refers to fats extracted from the seeds of plants. The “hateful eight” that critics often refer to include sunflower, soy, cottonseed, safflower, corn, ricebran, grapeseed, and canola oil. These ingredients are frequently criticized in health food circles, often blamed for everything from inflammation to chronic diseases. In reality, a lot of this seed oil craze is based on some truths but also many exaggerations, misconceptions, and misinformation.
Unhydrogenated seed oils are very high in omega-6 fats, a type of polyunsaturated fatty acid (PUFA) essential for human health. While this may initially sound like a positive, they are often very low in omega-3, another PUFA. Historically, the ratio of omega-6 to omega-3 that humans consumed in their diet was roughly 1-1. But consuming seed oils shifts that ratio to 20-1, and health influencers worry about it. Dr. Cate Shanahan (who coined the term “hateful eight”), Dr. Mark Hyman, and emerging wellness gurus on social media like Santa Cruz Medicinals argue that this ratio causes chronic inflammation. However, no large scale scientific studies have confirmed these claims so it is really hard to say. In spite of a lack of scientific evidence to back up these claims, it’s not unreasonable to be skeptical about consuming such high and unnatural amounts of omega-6.
Another concern is that seed oils are unstable at high temperatures. In deep frying, when oil is repeatedly used, this can become a problem. Under these conditions, the aforementioned PUFAs can turn into toxic and carcinogenic compounds like aldehydes, ketones, trans fatty acids, lipid peroxides, and polycyclic aromatic hydrocarbons: things that I don’t even know, but they don’t sound good. What is even more concerning, though, is that the US, unlike many EU countries, has no national regulation requiring oil replacement—which raises additional concerns on the buildup of these harmful compounds. EU countries such as Portugal, France, Germany, and Spain use sensory chemical tests to determine when frying oil must be discarded in restaurants and commercial kitchens. The US leaves the decision up to the companies, which could generate a substantial health risk for the public.
One talking point that is often brought up is that, during the manufacturing process, seed oils are extracted with hexane, which is toxic to humans with prolonged exposure. Therefore, small residual amounts remain in the oil. However, these hexane traces are so small, lower than the FDA and European Food Safety Authority’s limit of 1 ppm or part per million, that they are insignificant. I wouldn’t be worried about that at all: there are trace amounts of arsenic in our rice after all (from 0.1-0.66 ppm).
These concerns mainly apply to unhydrogenated seed oils. Oftentimes, deep frying is done in a blend of hydrogenated and unhydrogenated seed oils. Hydrogenated oils are much more stable at high temperatures, and don’t have any omega-6 fats. However, they contain many more saturated fats than unhydrogenated ones, which are bad for cholesterol and heart health (but not as bad as artificial trans fats). Overall, while this mixture may fix some of the health problems of unhydrogenated seed oils, it creates new ones. High-oleic seed oils, on the other hand, are derived from plants that are selectively bred to contain a high proportion of monounsaturated fatty acids (MUFA), which are very healthy and stable under high temperature. High-oleic seed oils are usually present as canola, sunflower, safflower, and soybean oils. While many critics will dismiss seed oils completely, these high-oleic forms should not be. Interestingly, high-oleic forms are favored in Europe where food manufacturers aim to meet EU health guidelines and public pressure to reduce saturated fats and meet strict limits on trans fats. Even McDonald’s uses high-oleic oil in Europe for deep-frying.
Frequently, anti-seed oil activists, neglecting the high-oleic options, will promote sometimes questionable alternatives. Beef tallow is frequently brought up, and while it has great heat stability and no PUFAs, it has a high amount of saturated fats, which, as I mentioned before, are bad. Avocado and olive oil, on the other hand, are some great alternatives that are also often brought up. Like high-oleic seed oils, they contain a high proportion of MUFA and are stable at higher temperatures (only for refined olive oil, but not extra virgin which can’t really be used for cooking). Both have the added advantage of being loaded with antioxidants, which are healthy. They are, however, more expensive than high-oleic seed oils.
I am not too worried by the concern healthy influencers frequently bring up: the omega-6 and omega-3 ratio deemed unbalanced and inflammatory. While I remain a little skeptical, the fact is that there is simply no conclusive scientific evidence to back this claim. What genuinely alarms me, though, especially considering the lack of regulations in the US, is the heat stability of these seed oils and the toxic chemicals that can be ingested as an outcome. In my opinion, it is best to avoid unhydrogenated seed oils and hydrogenated blends in the context of fast food restaurants and processed foods like chips. I would personally recommend switching to avocado or high-oleic oils for cooking, and buying snacks not cooked in regular (unhydrogenated) seed oils. To sum it all up, I believe that many of the criticisms of seed oils are exaggerated and misdirected and that they can still be enjoyed from time to time. I hope that, through this column, I have helped you, the reader, in making informed choices regarding your health, and while sharing facts and my own perspective, enabled you to form your own opinion. By focussing on evidence rather than fear, we can all navigate healthy eating more thoughtfully.
