As public concern rises over mounting health problems in younger and younger people, associated with the unrelenting obesity and diabetes epidemics, the spotlight of attention has turned to the components of the ultra-processed foods that line the shelves of our grocery stores. The foods have the benefit of being cheap (relatively speaking) and convenient, with remarkably long shelf lives. At first suspicions, were confined to the nature of the grains and the amount of sugar, especially in the form of high-fructose corn syrup in so many products. Could we blame them for weight gain and insulin resistance, especially since carbohydrates had become the base of the FDA recommended dietary pyramid in the 1970s, a change made to reduce saturated fat intake because of concerns about its relationship to heart disease? But since the early 2000s, food research has uncovered trouble with the other major component of so many packaged and processed foods – the vegetable oils that hold them together, and, more specifically, the category of vegetable oils derived from plant seeds.

By now, the average American diet includes 5-10 tablespoons of vegetable oil a day. While we need certain fats and fatty acids and a proper in the diet, with a proper balance between different types such as omega 3 and omega 6 fatty acids, their consumption in the form of vegetable oils is very different from their consumption in the form of whole foods. Prior to the development of vegetable oils in the early 20^th C, the dietary requirements for essential fats were easily met by the consumption of nuts, seeds, and animal products like lard, butter and tallow – the only fats available for eating and cooking. As whole foods though, 5-10 tablespoons of corn oil would require eating 98 ears of corn. The same amount of sunflower oil would take 2800 sunflower seeds.

 Seed oils are particularly rich in one fat called linoleic acid which is now known to cause weight gain, and a host of metabolic abnormalities including insulin resistance and oxidation of LDL-cholesterol, the so called “bad” cholesterol associated with heart disease. Oxidation is a chemical process that adds oxygen easily to unstable molecules and interferes with their function. It is thought to be related to many inflammatory processes associated with illness. There is also recent research suggesting that in order to participate in the development of plaques in arteries, LDL-cholesterol must be in an oxidized state.

Given the concentration of oils such as linoleic acid, as well as a host of other fatty acid and breakdown products in vegetable oils, it is conceivable that they do contribute to health problems like obesity and diabetes. Moreover, the chemical process used to make the vegetable oils into the solid oils that resist spoilage, increase shelf life and give foods nice textures, the process that introduced these oils into the human diet, was shown by the 1990s to increase rather than decrease heart disease, prompting legislation to cut the use of these substances in foods and sending food scientists back to the lab to find adequate substitutes. Combined with other observations suggesting that the massive change in dietary fats over the last 100 years also also contributed to cancer, gall stones and mood disorders it is reasonable to ask how such a striking change in diet came about and what to do about it now.

Two major events created and expanded the vegetable oil industry. The first was the industrial revolution that demanded lubricating oil. Just as the whaling industry was collapsing at the end of the 19^th C , machines made oil extraction from seeds efficient, and cottonseeds were plentiful. The second was the dietary advice given by the medical profession in the mid 1900s to avoid saturated fats and to replace them with the polyunsaturated fats in vegetable oils in an effort to curb the rising number of heart attacks. This advice came after the dietary cholesterol heart hypothesis won out over a sugar/insulin hypothesis as the cause of heart disease, and after polyunsaturated oils were shown to lower total cholesterol levels in studies that compared them to dietary saturated fat. In terms of safety ratings, vegetable oils were grandfathered in under the GRAS  (generally recognized as safe) category in food safety rules introduced in 1958, because by then they had been in use for half a century. They clearly were not toxic in the short term, but safety is measured over time in real world use. 

By the 1990s, when the vegetable comprised 9-10% of American caloric intake, the nature of the “trans fats” produced by hydrogenation of vegetable oils emerged. Instead of cutting heart disease, they had increased it.  Subsequent work in the 2000s showed that large numbers of poorly characterized and studied fats are produced by the hydrogenation process, with some contributing to insulin resistance and weight gain, prompting warning labels and sending food scientists back to the lab to find other methods of reducing oxidation of seed oils and make them structurally suitable for baked goods. The methods include genetic modification of seed crops (currently 90% of soybean crops are sown with GMO seeds), chemical processes known as interesterification, and attempts to make oils by fermentation of sugar cane or algae. The expense involved may erase any economic reasons for replacing animal fats, and the efforts are taking place on a background of serious questioning of the dietary heart hypothesis that prompted the shift away from saturated fats in the first place.

 So what should you do in his unsettled time when much of what we thought was settled science is in question, and when you want to do the best you can for your own health? First, recognize that there is truth in the statement that you are what you eat. Autopsy studies have shown that the laboratory made fats are found in cell membranes, which are the guardians of cell function. In addition, the chemical makeup of LDL cholesterol reflects the amount of vegetable oil in the diet and may be a crucial factor in the development of arterial plaques

Second, read labels and avoid products with hydrogenated or partially hydrogenated oils, as well as poorly defined oils. Know the names of the most common seed derived oils: soybean, corn, sunflower, safflower, grapeseed, peanut, cottonseed, rice bran, and canola (Canadian oil low acid, from the rapeseed). Olive oil and avocado oils are derived from plant fruits and are better choices. They contain mainly mono-unsaturated fats which are less prone to oxidation. In addition, they have higher heat points and therefore produce fewer toxic byproducts such as aldehydes in the cooking process. Coconut oil and palm oil, also made from the pulp of the plants, are saturated fats. They have made a comeback from the days when they too were considered risky for heart disease despite thousands of years of consumption by populations who did not develop the problem.

Third, be aware that the introduction of seed oils into the human diet parallels the rise in heart attacks that prompted the dietary attempts to cure the disease in the mid 20^thC, which in turn accelerated vegetable oil consumption. And significant declines in saturated fat consumption did not solve heart disease. There are, to be sure, other factors such as smoking involved, and many possible reasons for the health dilemmas facing us now, two decades into the 21^st C. But it is possible that the vegetable oils and more specifically the poly unsaturated seed oils that are modified in laboratory processes are a significant part of the problem. So it seems reasonable to try to understand them, to return to whole food sources of essential fats, and to keep consumption of these oils and the processed foods that rely on them as low as possible.