![]() Above the no effect level, 2,4-decadienal begins to show biological effects in rats and mice, including decreased body weight and stomach lesions after three months of oral feeding administered by gavage at levels up to 800 mg/kg. Compare this with the no adverse effect level reported for caffeine at only 3–5 mg/kg of body weight (equivalent to 3 cups of coffee) (Stavric 1998). This would be equivalent to no adverse effects after ingestion of up to 7 g by a 70 kg human, which is considered very low toxicity. In rats and mice, this compound has been found to have a “no adverse effect level” of 100 mg/kg of body weight. ![]() The oral LD50 (lethal dose for 50% of test animals) in rats is >5000 mg/kg. National Toxicology Program has compiled an extensive report on the toxicity of 2,4-decadienal (NIH 2011). ![]() This unsaturated aldehyde is formed in heated soybean oil in far higher amounts than any other aldehyde (Zhang et al. Oxidation of linoleic acid to trans, trans-2,4-decadienal.Ĭonsider the example of trans, trans-2,4-decadienal (the most stable isomer, referred to as 2,4-decadienal), a volatile aldehyde produced in vegetable oils by the oxidation of linoleic acid (Figure 1) that is responsible for much of the enticing aroma of fried food. But in sufficient quantities, some of these compounds can be toxic.įigure 1. These compounds produce the wonderful flavors of fried foods. During cooking, oxidation of fatty acids, both free and in triglycerides, produces very small amounts of dozens of new compounds called aldehydes, ketones, and alcohols. When it comes to the health aspects of cooking with vegetable oils, oxidation of the fatty acids is very important. All three chemical changes increase with cooking time and temperature and are accelerated by the presence of food. When cooking oils are subjected to heat in the presence of air and water (from food), such as in deep-fat frying and sautéing (pan frying), they can undergo at least three chemical changes: 1) oxidation of the fatty acids, 2) polymerization of the fatty acids, and 3) breaking apart of the triglyceride molecules into free fatty acids and glycerol by hydrolysis (reaction with water from the food being cooked) (Choe and Min 2007). This is supported by a Google Trends search of the words “cooking oil bad,” which shows that interest in this topic has doubled from 2008 to 2016 (Crosby 2018). Chan School of Public Health has received numerous comments and inquiries about the safety of cooking oils. In the last two years The Nutrition Source digital newsletter published by the Harvard T.H. Consumers have become increasingly concerned with the safety of cooking oils. Since 2003 consumption of all vegetable oils has increased by 157% in the United States. ![]() Other popular oils, such as olive, peanut, sunflower, safflower, coconut, sesame, avocado, and grape-seed oils, make up only a few percent of all the vegetable oils used in cooking and salads. Palm oil is the most consumed oil worldwide. ![]() Soybean oil alone amounted to 54% of all vegetable oil consumed by Americans in 2016, while soybean and canola oils together comprised 70% of the total. By 2016 soybean, canola, corn, and palm oils accounted for almost 90% of all vegetable oils consumed in the United States (USDA 2017). The commercial production of soybean oil in the United States began in the 1920s, and canola oil in Canada in the 1950s. Despite this long history of use, the vegetable oils now most commonly employed for cooking did not gain widespread use until the first half of the twentieth century. The use of vegetable oils from plants and fat from animals for cooking soon spread to the rest of Europe and Asia. Records also show the Greeks were deep-frying food in olive oil as early as the fifth century BCE. The Egyptians appear to be the first to cook food using palm oil as long ago as 3000 BCE (Before the Common Era). ![]()
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