SCOTT SIMON, HOST:
Various seed oils, including soybean, canola and safflower, are sometimes known as the Hateful Eight by critics. Health Secretary Robert F. Kennedy Jr. has said these oils are, quote, poisoning Americans. But as NPR's Maria Godoy found out, many health and nutrition researchers say those claims aren't supported by science.
MARIA GODOY, BYLINE: Peek into any kitchen pantry, and you're likely to run into a seed oil quickly.
CAITLIN DOW: My cooking oil here is canola oil.
GODOY: That's nutrition scientist Caitlin Dow with the Center for Science in the Public Interest, and this is her pantry. Her seed oils aren't limited to a bottle. They're in lots of different packaged foods.
DOW: So here I have Nilla Wafers, and this says vegetable oil. So it has palm oil and soybean oil.
GODOY: There's a bag of popcorn with sunflower oil and some oat milk made with canola.
DOW: What you'll find is that most processed foods, most foods that you're going to get in a bag or a box, are going to use seed oils as their oil.
GODOY: That's because seed oils are cheap, shelf-stable and neutral in flavor. So why are seed oils being vilified? Eric Decker is a food scientist at the University of Massachusetts Amherst. He says one common criticism is that seed oils are refined using hexane, a chemical solvent that helps draw the most oil out of a seed. That hexane is removed as part of the processing.
ERIC DECKER: But you end up with very small amounts left in the oil. Usually, these amounts are less than one part per million.
GODOY: Decker says these trace residue levels are too low to pose a health risk. But if you're concerned, you can avoid hexane by buying organic seed oils, which will be more expensive. Another common criticism is that seed oils promote inflammation. 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, quote, a "potential role in inflammation." He went further in this interview with Fox News last year.
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ROBERT F KENNEDY JR: Seed oils are one of the most unhealthy ingredients that we have in foods. And they are associated with all kinds of very, very serious illnesses, including body-wide inflammation.
GODOY: Nutrition scientist Sarah Berry of King's College London says this knock against seed oils is based on a misunderstanding of how the body processes the fats in these oils.
SARAH BERRY: Seed oils are particularly rich in the omega-6 polyunsaturated fats.
GODOY: Our bodies convert omega-6s into chemicals that promote inflammation, which is important if you need to stop bleeding, for example, or help a wound heal. Critics argue that if you consume too much omega-6, you're going to end up with chronic inflammation, which can lead to chronic diseases.
BERRY: Now, that all looks beautiful on a piece of paper, but it doesn't play out in real life. It doesn't play out in the human body, and there's randomized control trials consistently to support this.
GODOY: One researcher who's spent decades studying fatty acids is Tom Brenna of the University of Texas at Austin. He is concerned that people eat way too many omega-6s in their diet from seed oils. But he says you shouldn't stop eating them altogether.
TOM BRENNA: Some of the influencers are talking about getting rid of all of the omega-6 in the diet. That would be a terrible idea. So make sure you say some omega-6 is absolutely required. The question is how much.
GODOY: Brenna says he mostly sticks to olive oil, which he acknowledges is expensive. You can also look for seed oils that are labeled as high oleic. They have fatty acid profiles similar to olive oil.
BRENNA: Focus on a balanced diet. If you eat olive oil and fish, you will live forever.
GODOY: The one thing everyone we spoke with agrees with is that we eat too much ultra-processed food. Nutrition researcher Christopher Gardner of Stanford Medical School says ultra-processed foods are a main source of seed oils in our diet. But these foods also tend to be high in salt, sugar and fat.
CHRISTOPHER GARDNER: So is it the junk food that's causing these health issues, or is it the seed oils? And I have always thought it's the junk foods, not specifically the seed oils.
GODOY: He says if you're using seed oils to make a salad dressing or a stir-fry that gets you to eat more vegetables, that's ultimately a win for health.
Maria Godoy, NPR News. Transcript provided by NPR, Copyright NPR.
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