Until recently, “seed oils” was a term unfamiliar to most Americans, even though these oils are frequently used in cooking and food preparation. The phrase has gained popularity through internet influencers, wellness advocates, and some political figures, referring to common cooking oils like canola, soybean, and corn oil that have been staples in kitchens for decades.
Critics of these oils label them as “the hateful eight” and argue they contribute to health issues such as obesity and diabetes by causing inflammation. Robert F. Kennedy Jr., the newly appointed health secretary, has claimed that these oils are “unknowingly poisoning” Americans and suggested that fast-food restaurants should revert to using beef tallow, or rendered animal fat, in their fryers.
Reacting to consumer apprehension, several food manufacturers have eliminated seed oils from their products. Restaurants, including the salad chain Sweetgreen, have accordingly adjusted their menus. This mirrors a broader trend, as a survey by the International Food Information Council – an industry trade group – indicates many Americans now deliberately avoid seed oils.
This discourse has left nutrition scientists exasperated. Decades of research, they assert, have consistently confirmed the health benefits of consuming these oils, particularly when substituted for traditional alternatives like butter or lard. “I don’t know where it came from that seed oils are bad,” remarked Martha Belury, a food science professor at Ohio State University.
In a recent Senate hearing, Dr. Marty Makary, who is nominated to head the U.S. Food and Drug Administration, highlighted the need for a thorough review of seed oils. “I think seed oils are a good example of where we could benefit from a consolidation of the scientific evidence,” he suggested.
So, what exactly are seed oils? These are oils derived from seeds, commonly named by critics include canola, corn, cottonseed, grapeseed, soybean, sunflower, safflower, and rice bran oils. They undergo processing where seeds are pressed or crushed, followed by chemical and heat treatment to remove components that might leave the oil with a cloudy appearance or undesirable flavor and odor. The result is a clear, flavor-neutral oil that is both cost-effective and stable at high temperatures, according to Eric Decker, a food science professor at the University of Massachusetts Amherst.
Unlike seed oils, fruit oils such as olive oil and avocado oil are typically cold-pressed, preserving many of their plant-based health compounds but making them costlier and less heat stable. Seed oils are primarily composed of unsaturated fatty acids, which include monounsaturated and polyunsaturated fats. Most are high in omega-6 fatty acids and lower in omega-3s. These essential fatty acids are crucial for health because our bodies aren’t capable of producing them.
There are various health claims regarding seed oils, often deemed unsubstantiated by scientific research. Some critics allege that production processes leave toxic by-products, like hexane. However, Decker clarifies that the hexane used in extraction evaporates, leaving remnants that “are very low and would not present a risk.”
Others suggest that the oils’ high omega-6 content causes an imbalance promoting inflammation and chronic diseases. However, Belury, who has studied fatty acids for 30 years, argues that this is a mistaken simplification. Research indicates increased linoleic acid, a prevalent omega-6, does not significantly elevate inflammation markers. “Scientists who study omega-6 and omega-3 think we need both,” she insisted, stating that seed oils do not enhance inflammation markers.
Furthermore, research, including by the American Heart Association, consistently demonstrates that replacing saturated fats with plant-based oils can lower bad cholesterol and reduce heart disease and stroke risk. As further affirmed by recent research from Brigham and Women’s Hospital, a study following over 200,000 adults over 30 years found those consuming the most butter had a 15% higher mortality risk than those consuming less. Conversely, those ingesting the most plant-based oils, including seed oils, faced a 16% lower risk.
Dr. Daniel Wang, who spearheaded this study, suggests that merely substituting less than a tablespoon of butter with equivalent plant-based oil calories daily could potentially curtail premature deaths by 17%, a “substantial benefit,” he stated.
The consumption of seed oils has surged, as noted by groups like the Seed Oil Free Alliance, which certifies products free of such oils. They contend these oils offer empty calories, replacing more nutritious foods. Corey Nelson, co-founder of the alliance, believes consumers deserve the option to avoid seed oils in favor of other product adjustments, like low-sodium or low-sugar versions.
Although experts concur that seed oil usage has risen, this trend is attributed to their prevalent incorporation in fried, fast, and ultra-processed foods, comprising almost three-quarters of the U.S. food supply. These food categories, associated with various health problems, are rich in refined grains, added sugars, and sodium. Yet, experts point out no evidence suggesting that seed oils alone are culpable for adverse health outcomes.
For individuals wary of seed oils, experts recommend reducing intake of ultra-processed foods and seeking tailored dietary advice. Decker suggests diversifying oil use according to health conditions. While olive oil remains the healthiest option, practical usage should consider individual cooking preferences and budget constraints. For Omega-3 enhancement, consuming more fish like tuna and salmon is advised.
Both advocates and critics of seed oils agree that further nutrition research is pivotal to settling longstanding debates. However, replacing seed oils with beef tallow, characterized by high saturated fat, isn’t considered beneficial. “There is no evidence to indicate that beef tallow is healthier than seed oils,” Decker emphasized, recognizing that tallow also undergoes processing for purification.
