Scientific review published in Advances in Nutrition finds that when heated these oils can have detrimental effects on human health

The consumption of omega-6 polyunsaturated fatty acid (PUFA)-rich vegetable oils such as canola, soybean, sunflower, and corn oil has increased 1,000-fold since 1960, in part because these oils are believed to be healthier alternatives to saturated fats.  Omega-6 PUFA-rich vegetable oils are now the most widely consumed cooking oils in the home and in restaurants worldwide.  Nonetheless, very little data are available on the risks these oils may pose for human health.  In particular, the rise of omega-6 PUFA-rich vegetable oil consumption in the United States coincides with the explosive rise in diseases labeled “lifestyle diseases,” including Alzheimer’s disease, obesity, type 2 diabetes, and other inflammatory disorders.

Published in Advances in Nutrition, the international review journal of the American Society for Nutrition, “Intake of Omega-6 Polyunsaturated Fatty Acid-Rich Vegetable Oils and Risk of Lifestyle Diseases” examines the evidence to see if, in fact, there are links between the consumption of omega-6 PUFA-rich vegetable oils and the rise of a broad range of lifestyle diseases.

When heated, omega-6 PUFA-rich vegetable oils generate a substance known as hydroxynonenal, which researchers now believe plays a key role in cell degeneration and cell death.  The authors, therefore, focused much of their attention on how hydroxynonenal derived from omega-6 PUFA-rich vegetable oils affects human health.

Examining the link between hydroxynonenal and Alzheimer’s disease, for example, the authors found “strong postmortem and experimental evidence concerning hydroxynonenal-induced oxidative damage occurring in Alzheimer’s patients.”  In particular, research studies have found elevated concentrations of hydroxynonenal among Alzheimer’s patients, compared with age-matched controls, in the brain regions that are closely related to memory functions.  The authors therefore pointed to omega-6 PUFA-rich vegetable oil-derived hydroxynonenal as “the real culprit” underlying the cell degeneration and cell death that causes Alzheimer’s disease.

Apart from hydroxynonenal, omega-6 PUFA-rich vegetable oils in general have been implicated in the rise of lifestyle diseases.  For example, the authors noted that “fatty acid composition rather than the amount of fat, may actually be the key factor inducing obesity.”  More specifically, a higher percentage of omega-6 PUFAs in the diet increases appetite and adipose tissue inflammation, which, in turn, can lead to obesity.

In summarizing their findings, the authors highlighted three key points.  First, omega-6 PUFAs are essential fatty acids; however, they have a “very narrow therapeutic window.”  Second, too much omega-6 PUFAs disrupts normal healthy function.  Third, the authors stressed that excessive omega-6 PUFA intake is equivalent to any amount above 0.4% of total food energy intake.  In conclusion, the authors believe that decreasing the consumption of omega-6 PUFA-rich vegetable oils while at the same time increasing the consumption of omega-3 PUFA-rich fish oils is needed to prevent a range of lifestyle diseases.

Reference Tetsumori Yamashima, Tsuguhito Ota, Eishiro Mizukoshi, Hiroyuki Nakamura, Yasuhiko Yamamoto, Mitsuru Kikuchi, Tatsuya Yamashita, Shuichi Kaneko, Intake of ω-6 Polyunsaturated Fatty Acid-Rich Vegetable Oils and Risk of Lifestyle Diseases, Advances in Nutrition, nmaa072,

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