Fat Guide
Are seed oils bad for you?
Few foods have swung from health-recommended to internet-villain as fast as seed oils. The underlying evidence has moved much less than the discourse.
What they are
"Seed oils" usually refers to soybean, canola (rapeseed), sunflower, safflower, corn, cottonseed, grapeseed, and rice bran oil. What they share is being high in polyunsaturated fat, particularly the omega-6 fatty acid linoleic acid.
The argument against them
The common claim runs: omega-6 fats are pro-inflammatory, modern diets contain far more omega-6 than our ancestors ate, therefore seed oils drive chronic disease. The omega-6 to omega-3 ratio has genuinely shifted in modern diets — that part is accurate.
What the evidence actually shows
The American Heart Association's presidential advisory reviewed the randomized controlled trials and pooled analyses and concluded that replacing saturated fat with polyunsaturated vegetable oil lowers cardiovascular disease risk — by about 30% in the pooled trial data, an effect comparable to statin treatment.[1]
The proposed inflammation mechanism has also not held up well: controlled feeding trials increasing linoleic acid intake have generally not shown corresponding increases in inflammatory markers in humans.[1]
The reasonable middle
A fair reading is that seed oils are not the problem — but the foods they most often arrive in might be. Most seed oil in a typical diet comes packaged inside fried and ultra-processed food, and that association is easy to mistake for causation by the oil itself. Getting more omega-3 is better supported than fearing omega-6.
Keep reading: Omega-3 vs omega-6 · Saturated vs. unsaturated fat · Common nutrition myths