Summary
This study investigated whether increasing polyunsaturated vegetable oil intake—specifically corn oil—could help people with ischaemic heart disease live longer or avoid additional heart attacks, a question rooted in 1960s beliefs that lowering cholesterol with high–linoleic acid oils might protect the heart. Eighty patients with confirmed disease were randomly assigned to one of three groups: a control group with no diet changes, an olive-oil group consuming 80 grams of olive oil daily with reduced animal fat, and a corn-oil group consuming 80 grams of corn oil daily with reduced animal fat. Over two years of monitoring, researchers found that corn oil lowered cholesterol markedly, while olive oil had little impact. Yet the most important outcomes—survival and reinfarction rates—told a different story: 75% of the control group remained alive and free of major cardiac events, compared with only 57% in the olive-oil group and 52% in the corn-oil group, the worst outcomes despite the greatest cholesterol reduction. Many patients also struggled to tolerate the large oil doses, experiencing nausea, diarrhoea, and poor adherence. Overall, lowering cholesterol with high-PUFA corn oil did not benefit heart-disease patients and may have increased risk, leading the authors to conclude that corn oil is unlikely to be helpful—and may even be harmful—while olive oil also failed to improve clinical outcomes. This early controlled trial remains notable for demonstrating that cholesterol lowering alone does not guarantee better survival in heart disease.
PMID: 14288105
PMCID: PMC2166702
DOI: 10.1136/bmj.1.5449.1531
Abstract
Background: Dietary polyunsaturated fats were widely hypothesized to reduce cardiovascular risk through serum-cholesterol lowering, yet no well-controlled clinical trial had tested whether replacing dietary saturated fats with unsaturated vegetable oils improved outcomes in patients with established ischaemic heart disease.
Objective: To evaluate the effects of two unsaturated oils—corn oil (high in polyunsaturated linoleic acid) and olive oil (rich in monounsaturated oleic acid)—on serum cholesterol levels and clinical progression of ischaemic heart disease.
Methods: Eighty patients with documented ischaemic heart disease were randomly assigned to one of three groups: (1) a control group with no dietary advice; (2) an olive-oil group receiving 80 g/day of olive oil plus dietary fat restriction; and (3) a corn-oil group receiving 80 g/day of corn oil plus dietary fat restriction. Patients were followed for two years. Serum cholesterol was measured longitudinally, and clinical outcomes—including fatal and nonfatal myocardial infarction—were recorded as major cardiac events.
Results: Corn oil produced significant reductions in serum cholesterol across multiple intervals, whereas olive oil showed no significant change; controls remained stable. Despite cholesterol reduction, clinical outcomes did not improve. By two years, 75% of control patients remained alive and free of reinfarction, compared with 57% of those receiving olive oil and 52% of those receiving corn oil. The worse outcomes in the corn-oil group approached statistical significance (P ≈ 0.05–0.1). Adherence to the prescribed oil dose declined over time due to intolerance (distaste, nausea, diarrhoea).
Conclusions: In patients with established ischaemic heart disease, high-dose corn oil lowered serum cholesterol but did not improve—and may have worsened—clinical outcomes compared with controls. Under these conditions, corn oil cannot be recommended as a therapeutic intervention for ischaemic heart disease.
ROSE GA, THOMSON WB, WILLIAMS RT. CORN OIL IN TREATMENT OF ISCHAEMIC HEART DISEASE. Br Med J. 1965 Jun 12;1(5449):1531-3. doi: 10.1136/bmj.1.5449.1531. PMID: 14288105; PMCID: PMC2166702.