Seed Oils as a Hypothesized Contributor to Heart Disease: A Narrative Synthesis

Coronary heart disease (CHD) was relatively uncommon in the 19^th century, when infectious illnesses dominated mortality, but it rose dramatically in the 20^th century in parallel with major dietary shifts, including an increase in linoleic acid (LA), an essential omega-6 polyunsaturated fatty acid (PUFA) abundant in vegetable oils. This review examines whether the rapid, unprecedented rise in consumption of LA-rich industrial seed oils may have played a contributing role in the escalation of CHD. Historical trends in CHD and overall cardiovascular mortality were examined in relation to shifts in dietary fat sources, especially seed oils, and mechanistic studies were reviewed to assess how excessive LA intake could promote atherosclerosis through oxidative stress and inflammation. Multiple lines of evidence were integrated, including early 20^th-century mortality records, data on dietary fat supply, and findings from experimental studies. Available data indicate that per capita seed oil consumption rose sharply in the early 1900s, preceding the surge in CHD deaths by one to two decades, roughly the time frame needed for atherosclerotic plaques to develop. Soybean oil, in particular, went from virtually no use at the start of the century to a dominant dietary fat by its end, more than doubling the proportion of LA in the food supply and coinciding with a marked rise in LA content within human tissues.  Mechanistic studies further show that LA oxidation can generate reactive aldehydes, such as 4-hydroxynonenal (4-HNE), which have been shown to trigger inflammatory and oxidative pathways. These include activation of the transcription factor NF-κB, which regulates immune signaling, and up-regulation of the protein Bcl-2, which promotes cell survival. These effects can impair endothelial functions central to atherogenesis. While other factors, like cigarette smoking and improved diagnostic tools, also likely contributed to a rise in reported CHD rates, these patterns may not fully account for the magnitude or timing of the mid-century heart disease surge. Taken together, the historical, epidemiologic, and mechanistic evidence suggests that excessive consumption of LA-rich seed oils may have been a significant, under-recognized contributor to the 20th-century CHD epidemic. Reducing the intake of these oils and rebalancing the fatty-acid profile of the diet may therefore be a practical strategy to mitigate CHD risk in modern populations.