Component 1 (fats and heart health) is directly and strongly supported by primary sources.

The 2017 AHA presidential advisory in Circulation concluded that randomized controlled trials which lowered dietary saturated fat and replaced it with polyunsaturated vegetable oil reduced cardiovascular disease by approximately 30 percent, a magnitude the advisory compared to statin treatment.

The 2020 Cochrane review of randomized trials (15 studies, roughly 56,000 to 59,000 participants, evidence current to October 2019) found that reducing saturated fat intake for at least two years produced about a 17 percent reduction in combined cardiovascular events, with little effect on mortality. Cochrane specifically stated that replacing saturated fat energy with polyunsaturated fat or carbohydrate appeared to be useful strategies, while replacement with monounsaturated fat was unclear.

The 2025 JAMA Internal Medicine cohort study of roughly 200,000 people followed over 30 years found higher plant-based oil intake, specifically naming soybean and canola alongside olive oil, associated with lower total, cancer, and cardiovascular mortality, while higher butter intake was associated with increased total and cancer mortality. Substituting 10 g/day of butter with plant oils was associated with reduced mortality.

Biomarker evidence points the same direction. The 2024 UK Biobank analysis in the American Journal of Clinical Nutrition (n=257,925) found plasma linoleic acid, the dominant omega-6 fat in most seed oils, inversely associated with total and cause-specific mortality.

Institutionally, the AHA has stated there is no evidence supporting avoidance of seed oils, and its 2026 dietary guidance scientific statement promotes liquid nontropical plant oils such as soybean and canola, citing strong evidence that replacing butter, beef tallow, and tropical oils with plant oils lowers LDL cholesterol.

Component 2 (attribution of ultra-processed food harm) is partially supported but not settled.

There is genuine expert support for the idea that seed oils are not the driver of harm in ultra-processed foods, and that the overall food matrix matters more. However, the specific attribution to sodium, added sugars, and refined carbohydrates is contested by current research. A 2026 Tufts study in the American Journal of Public Health found that higher ultra-processed food intake was associated with worse health outcomes even after accounting for saturated fat, added sugar, and sodium, and the authors suggested that factors beyond nutrients, such as changes to cellular food structure, loss of beneficial compounds, additives, and packaging chemicals, may create risks not captured by traditional nutrient measures. In other words, current evidence indicates the harm is likely not attributable to seed oils specifically, but it also does not confirm that sodium, sugar, and refined carbs fully explain it.