What’s Wrong With Vegetable Oil?

Doctors tout it as a heart-healthy alternative to saturated fat. It’s in everything – packaged food, fast food, gourmet restaurant food, “health” food. But the truth is, vegetable oil is a highly processed, worse-than-empty calorie pseudo-food. And it has nothing to do with vegetables.

“Vegetable” oil is actually made from seeds – corn kernels, soy beans, sunflower seeds, safflower seeds, rapeseeds, cotton seeds – most of which don’t contain much oil to begin with (how much oil is in a kernel of corn?). Forcing oil from non-oily seeds requires intensive processing – either mechanical (using a machine to press the oil from the seed) or chemical (using a solvent such as petroleum-derived hexane). The result of all this crushing and dissolving is a crude oil that must be filtered and deodorized before it is considered edible. Some of the oil is also partially hydrogenated, a process that makes it less susceptible to oxidation (aka going rancid), but also produces trans fat, saturated fat’s evil alter-ego.

This leads to another point, which is that unhydrogenated vegetable oil is not very stable at room temperature, meaning it goes rancid easily. Rancid oils are just as bad as they smell – they contain free radicals which can wreak havoc in human cells and lead to cancer. Heating vegetable oil causes even more oxidation, which is why a lot of the oil used in deep fryers in fast food joints and restaurants is hydrogenated. Why doctors think it’s a good idea to ingest large quantities of oxidized oil, or worse, cook with it, is beyond me.

The energy and technology required to extract oil from non-oily plants and the impossibility of keeping it fresh without refrigeration explains why humans did not start consuming vegetable oil until last century. For the first few million years of human existence, the only types of fat people ate in large quantities were saturated fat (found in animals and some fruits like coconut and palm) and monounsaturated fat (found in animals and some fruits and nuts like olives and almonds). They got a little bit of polyunsaturated fat (the type of fat found abundantly in vegetable oil) from animals, nuts and seeds, but the amounts were tiny in comparison. There is no traditional food that provides anywhere near the amount of polyunsaturated fat found in vegetable oil. This means that humans have had effectively zero time to adapt to its biological effects, the full extent of which researchers don’t yet understand.

Apart from the sheer quantity of polyunsaturated fatty acids, there is the problem of the type of polyunsaturated fat people are eating. Polyunsaturated fat comes in two types, n-6 and n-3 (also call omega 6 and omega 3). Both are essential fatty acids, which means people need to eat them to live, but are required only in small quantities, like a few grams per day. It’s easy (all too easy) to get enough n-6 just by eating normal amounts of meat, poultry, eggs, nuts, seeds, or the tiniest bit of vegetable oil. With a modern diet, getting enough n-3 is a lot trickier, since it’s only found in significant quantities in fish, algae, seafood, fish oil, flax seed and some nuts (which also contain a lot of n-6). This means that a lot of people in industrialized countries are probably n-3 deficient, with a ratio of n-6 to n-3 between 10:1 and 30:1. This ratio is astronomical compared to the ratio consumed by traditional cultures, usually between 2:1 and 1:1.

The ratio is important because n-6 and n-3 perform different and competing functions in the body. They are both used to manufacture eicosanoids, signaling molecules that control inflammation and act as messengers in the central nervous system (according to wikipedia). Very simplistically speaking (eicosanoids are diverse, complex and still poorly understood), eicosanoids made from n-6 are pro-inflammatory (they turn on immune response) while eicosanoids made from n-3 are anti-inflammatory (they turn off or reduce immune response). Inflammation in response to injury or infection is a good thing – it’s how the body quarantines and neutralizes harmful agents. But chronic inflammation, which can be caused by an imbalance between pro-inflammatory and anti-inflammatory eiconasoids, is dangerous, and probably involved in most or all of the non-communicable diseases that plague industrial nations, such as heart disease, cancer, auto-immune diseases, allergies, asthma, metabolic syndrome and mental illness. The ratio of n-6 to n-3 in the diet determines the ratio of n-6- to n-3- derived eicosanoids in the body. Consuming vegetable oil guarantees over-consumption of n-6, creating an imbalance even high dose fish oil supplementation won’t reverse (though fish oil can reverse n-3 deficiency, which is nothing to scoff at).

In summary, vegetable oil is a new-fangled, highly processed substance that humans have not evolved to eat. It goes rancid at the drop of a hat and contributes to chronic inflammation and disease. Unfortunately, it has invaded our food supply, aided and abetted by public health officials terrified of saturated fat, a real food our ancestors evolved to eat. Today it is almost impossible to avoid vegetable oil except by cooking food at home, using traditional animal fat or healthy oils such as olive, palm, avocado or coconut oil (incidentally, all fruit oils). The sudden influx of easily oxidized n-6 polyunsaturated fat into our food supply presents a challenge for which our bodies are completely unprepared. It’s a human experiment of massive proportions with a fast-dwindling control group. We are already seeing the results, in the skyrocketing incidence of degenerative, inflammation-driven diseases.




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