Vegetable oils are just fats \u2013 they have no carbs, and they prompt no immediate blood sugar or insulin surge, issues of particular importance both to keto dieters and people with diabetes. And many mainstream health authorities, such as the American Heart Association, tout veggie oils as healthy options. So, what\u2019s the big deal?<\/p>\n
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Defining Industrial Seed Oil<\/h3>\n
\u201cVegetable oil\u201d is a broad category, too broad for our purposes \u2013 any oil extracted from a plant can be technically considered a vegetable oil, from corn oil to cocoa butter.<\/p>\n
What we\u2019re really talking about are vegetable oils that are extracted from seeds using modern processes on an industrial scale. For the most part, that\u2019s soybean, canola, and corn oil: those three alone make up some 75% of the added fats market, and constitute an enormous percentage of America\u2019s calorie intake. Some other less common oils, such as safflower and cottonseed oil, fall into the same category.<\/p>\n
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The Rise of \u201cSalad and Cooking Oils\u201d<\/h3>\n
Mistrust of vegetable oils starts with a simple correlation: over the past several decades, as diabetes and obesity have spiraled out of control, we\u2019ve been eating more and more of these oils. Take a look at this chart from the Pew Research Center:<\/p>\n
![\"Modern](\"https:\/\/asweetlife.org\/wp-content\/uploads\/2020\/05\/Graph-Canola-Oil.png\")
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Americans are eating more than ever, and the gain is almost entirely concentrated in two food groups: grains and fats. That grains have contributed to the obesity epidemic will be no surprise to most ASweetLife readers. The contribution of fats might be a little bit more intriguing. The entirety of that increase was concentrated in the \u201csalad and cooking oils\u201d category. According to the USDA<\/a>, in 1970 there were about 15 pounds of salad and cooking oils bought and consumed for every consumer; by 2010 that number had increased to over 50 pounds, and is only expected<\/a> to keep increasing. Meanwhile, the use of all other cooking fats under consideration \u2013 butter, lard, shortening and so on \u2013 actually declined by about 10 pounds per year, or 33%.<\/p>\n The massive increase in salad and cooking oil consumption is probably the single most dramatic dietary change for Americans since the dawn of the obesity epidemic. (While a small percentage of this increase represents the increasing popularity of olive oil, the rise is almost entirely the doing of the usual suspects, soybean, canola, corn and friends.) Levels of meat, vegetable, dairy, fruit and even sugar consumption have stayed mostly steady, with some changes within categories (eg more chicken, less beef; more cheese, less milk). Correlation is not causation, and therefore this is no smoking gun, but it\u2019s been enough to provoke widespread mistrust of this particular nutritional change.<\/p>\n Putting the Industry in Industrial<\/strong><\/p>\n There is also a deep skepticism regarding the history and manner of seed oil production. These oils are largely extracted using advanced processes and many chemicals, all to produce an ingredient that our more metabolically-healthy ancestors would never have recognized<\/a>.<\/p>\n Consider, if you will, canola oil. Canola oil is extracted from a variety of the rapeseed plant, an unfortunately-named relative of nutritional superstars like broccoli and mustard. So far, so good, right?<\/p>\n Rapeseed oil has been cultivated almost from time immemorial, but for its first several thousand years, it wasn\u2019t very popular as a food. The rapeseed is naturally very high in erucic acid, a substance that is toxic in large doses and gives the oil a distinct flavor that must have never caught on. It found its greatest popularity after the invention of the steam engine, when it was found to be a superb engine lubricant.<\/p>\n In the 60\u2019s Canadian scientists began to breed rapeseeds to reduce the toxin levels and emphasize other desirable characteristics. By 1978 they had hit on a winning genetic combination, and trademarked the name \u201cCanola.\u201d It was not sold in the US until 1985, when the FDA declared that it could be classified as a Generally Recognized as Safe. Soon thereafter its popularity skyrocketed, and it won many awards from health and nutrition societies. Pesticide-resistant GMO varieties soon followed, and now dominate the market.<\/p>\n How is canola oil made<\/a>? The seeds are cooked, flaked, then cooked again. Some oil may be extracted the traditional way, with a press, but the rest is harvested through the use of a solvent named Hexane, a byproduct of crude oil production. More refining steps follow: the crude canola oil is subjected to multiple additional processes to result in a clean, colorless, odor-free and shelf-stable product.<\/p>\n These oils are modern marvels of science, but all this processing and refining raises suspicions. Are we really supposed to eat something like this, that our ancestors never did? A 2018 study<\/a> found that \u201cthe refining processes destroy its nutritional values.\u201d<\/p>\n Canola oil also has many industrial applications: the Manitoba Canola Growers<\/a> proudly boast of non-edible uses such as \u201csoftening agent for applying plastic casings on window panes\u201d and \u201cmold releaser in metal fabrication.\u201d<\/p>\n Omega 6:3 Ratio<\/strong><\/p>\n You\u2019ve probably heard that Omega-3 fatty acids are very good for you. Less well-known are Omega-6 fatty acids, which are \u2026 complicated. Omega-6 fatty acids aren\u2019t necessarily unhealthy, and many healthy whole foods contain good amounts of them, including eggs, nuts, and seeds. Too much, though, looks like a bad idea.<\/p>\n Many experts have focused on the ratio of Omega-6 to Omega-3 fatty acids in our diet as a convenient way to analyze the healthiness of our fat intake. Anthropological estimates suggest that for most of our long evolutionary history, humans consumed a ratio of Omega-6 to Omega-3 of about 1:1. Today, that ratio is badly out of whack: a 2002 study<\/a> found that it had grown to at least 16:1.<\/p>\n Our Omega-6 consumption is so out of whack largely because of the huge amount of industrial seed oils in our diet. Corn oil is the most flagrant offender here: its ratio is something like 50:1. Soybean, cottonseed, palm and many other oils also tip the scales at 15:1 or worse. (Canola oil is actually an exception, with a ratio of 2:1). Animal fat sources, which used to make up a much larger percentage of America\u2019s fat consumption, tend to have Omega-6 to Omega-3 ratios of close to 2:1.<\/p>\n Many theorize that this imbalance has grave health consequences. Researchers have argued that the excess of Omega-6 fatty acids \u201cpromotes the\u00a0pathogenesis\u00a0of many diseases, including cardiovascular disease, cancer,\u00a0osteoporosis, and inflammatory and\u00a0autoimmune diseases<\/a>\u201d and that that inflammation caused by these acids contribute to \u201cnumerous chronic diseases such as rheumatoid arthritis, atherosclerosis, dyslipidaemia, diabetes, obesity and heart failure<\/a>.\u201d<\/p>\n <\/p>\n Insulin Resistance<\/strong><\/p>\n Most of those bad health outcomes are still subject of study and debate, and we cannot declare definitively that industrial seed oils are linked with these diseases. But one of the strongest links, and one of particular interest to readers with diabetes, appears to be between seed oils, obesity, and insulin resistance.<\/p>\n Some of this data comes from animal studies. For instance, a high corn oil diet induced insulin resistance in mice<\/a> (and made them measurably lazier too!), and that a diet high in soybean oil \u201cis more detrimental to metabolic health than a diet high in fructose or coconut oil<\/a>.\u201d It\u2019s not just mice, of course: even maternal Omega-6 intake is associated with excessive infant weight gain<\/a>.<\/p>\n