In this 2018 article, James DiNicolantonio and James O’Keefe (St. Luke’s Mid America Heart Institute) review the evidence that linoleic acid is a harmful—and possibly causal—driver of heart disease.
Linoleic acid (a polyunsaturated fat) is a major fatty acid in vegetable oils: It makes up over 50 percent of soybean oil, corn oil, sunflower oil, and many similar substances. Since the late 1950s, vegetable-oil consumption (and thus consumption of linoleic acid) has increased dramatically in the U.S., rising from under four percent to eight to 10 percent of our total energy intake.
Multiple pieces of evidence suggest linoleic acid plays a role in heart-disease progression. A major heart-disease model suggests low-density lipoproteins must be oxidized to begin forming plaques (oxidized LDL cannot be recycled by the liver but can be recognized by macrophages, leading to foam-cell development). Linoleic acid is more susceptible to oxidation than other fatty acids and is the most commonly oxidized fatty acid found in LDL; oxidized linoleic acid derivatives are frequently found in plaques, and the amount of these fatty acids found in plaques correlates with disease severity. Additionally, multiple clinical trials—e.g., the Sydney Diet Heart Study (1) and Minnesota Coronary Experiment (2,3)—have shown that replacing saturated fats with polyunsaturated fats generally or linoleic acid specifically increased all-cause and/or coronary mortality.
A diet-heart hypothesis view will suggest linoleic acid is cardioprotective because replacing saturated fat with linoleic acid will reduce total and LDL cholesterol levels (3). However, the evidence regarding oxidation of linoleic acid suggests these markers fail to capture the whole picture, and linoleic acid in fact increases cardiovascular risk directly. This, in turn, suggests the dramatic increase in vegetable-oil consumption in western diets may have contributed to the increase in cardiovascular mortality.
- Ramsden CE, Zamora D, Leelarthaepin B, Majchrzak-Hong SF, Faurot KR, Suchindran CM, Ringel A, Davis JM, and Hibbeln JR. Use of dietary linoleic acid for secondary prevention of coronary heart disease and death: evaluation of recovered data from the Sydney Diet Heart Study and updated meta-analysis. BMJ 346(8707), 2013. Available here.
- O’Connor A. A decades-old study, rediscovered, challenges advice on saturated fat. The New York Times. April 13, 2016. Available here.
- Ramsden CE, Zamora D, Leelarthaepin B, Majchrzak-Hong SF, Faurot KR, Broste SK, Frantz RP, Davis JM, Ringel A, Suchindran CM, Hibbeln JR. Re-evaluation of the traditional diet-heart hypothesis: analysis of recovered data from Minnesota Coronary Experiment (1968-73). BMJ 353(1246), 2016. Available here.