Unsung benefits of darker, tasty oils

From San Francisco, at the spring national meeting of the American Chemical Society

Antioxidants may help limit the ravages of chronic diseases such as cancer and heart ailments by quashing cellular damage from molecular fragments known as free radicals. Though vegetable oils often start out with large quantities of radical-quenching antioxidants, a new study finds that the processing to get rid of oils’ distinctive flavors and colors deactivates or removes such compounds.

Biochemist Hiroshi Maeda of Kumamoto University School of Medicine in Japan and his colleagues surveyed a variety of the most popular cooking oils. They found that unprocessed olive oils were especially effective in scavenging the free radicals unleashed by a destructive oxidant—a peroxyl radical chosen to mimic those that can form when meat and dietary metals, such as iron, come together in the gut. Newly pressed oils from rape (canola) and sesame seeds showed just 5 to 10 percent of the activity measured in the virgin olive oils; corn and safflower oils were somewhat less potent than the canola and sesame oils.

However, the scientists report, the processed oils available in a grocery store had lost any detectable activity against the test oxidant. Concludes Maeda: Consumers who cultivate a taste for minimally processed oils might derive health benefits.

Janet Raloff

Janet Raloff is the editor of Science News for Students, a daily online magazine for middle school students. She started at Science News in 1977 as the environment and policy writer.

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