Health Secretary RFK Jr. has said vegetable oils, like canola and soybean, are ‘poisoning Americans.’ But many researchers say the evidence isn’t there. So, what does the science say about seed oils?
By now, you might have heard that seed oils are bad for you — if not from social media wellness influencers, then from Health Secretary Robert F. Kennedy Jr. himself.
Kennedy has said these vegetable oils — extracted from the seeds of plants, like canola, soybean and safflower — are poisoning Americans and driving the obesity epidemic. Part of the evidence he points to is that obesity rates started to rise as seed oils began to dominate the American diet.
Many nutrition and health researchers say while seed oils might not be as good for you as olive oil, claims that they’re harmful to health have been stretched too far.
«This is one of the more studied topics in nutrition. So it’s sort of extra bewildering to quite a few of us in the field that this is coming up», says Christopher Gardner, a nutrition scientist and professor of medicine at Stanford University.
He says studies have consistently shown that replacing saturated fats, such as lard or beef tallow, with fats from plant oils leads to better health outcomes.
Still, Kennedy celebrated when the fast-food chain Steak ‘n Shake announced earlier this year that it would stop making its French fries with seed oils and use tallow — rendered beef fat — instead.
When we reached out to Secretary Kennedy, his team pointed us to the MAHA report, which says that seed oils contribute to imbalances of fatty acids that play «a potential role in inflammation.»
So what is the science on seed oils? Let’s unpack some of the criticisms.Refining with chemicals and heat
Critics tend to focus on eight specific oils, sometimes referred to as the «hateful eight:» soybean, canola, corn, cottonseed, sunflower, safflower, rice bran and grapeseed.
To maximize how much oil is drawn out of these seeds, manufacturers usually process them using heat and chemicals, explains Eric Decker, a professor emeritus of food science and lipids researcher at the University of Massachusetts Amherst. It’s a cheaper and more efficient process than mechanically pressing the oil out. By comparison, extra virgin olive oil is squeezed out of the fruit without the help of chemicals or heat.
Decker says critics often raise concerns about the most commonly used solvent in refining seed oils — hexane — which is hazardous. The hexane is removed during processing, «but you end up with very small amounts left in the oil», he says.
However, Decker says these residues are at levels too low to be toxic. A toxicology report from the federal government, published in April 2025, called the amount «toxicologically insignificant.» And any residual hexane is likely to evaporate once you heat your oil during cooking, Decker says.
Caitlin Dow, a senior nutrition scientist with the Center for Science in the Public Interest, says she’s personally not concerned about hexane residues in seed oils, but if you are, you can always buy organic seed oils — they aren’t processed with hexane, but they do cost more.
