Could you eat 98 ears of corn in one sitting? That is essentially what you are doing when you consume 5 Tbsp of corn oil. When I am trying to think out whether something should be included in the human diet, I always look into when it entered the human diet. Things that have been in the diet for millions of years are likely beneficial as we evolved eating them and things that have entered since chronic disease has taken off (last 50-100 years) should be met with more skepticism. Seed oils, very high in the omega-6 fat linoleic acid, fit the bill for things that have entered in the human diet in the last 100 or so years and thus should be examined as a candidate for chronic disease.
These fats entered the diet in about 1910, but didn’t really take off until the 1950s. At the time they came into play, the leading causes of death in this country were pneumonia and TB. By 1920, the leading causes of death were heart disease and cancer. Chronic disease levels in our society has tracked very well with the amount of these oils in our diet, but correlation isn’t causation. Observations like this are for generating hypotheses that can then be tested. So let’s test the hypothesis that seed oils are a potential cause of chronic disease in this country.
If we go back to organic chemistry (everyone’s favorite class!), we will remember that polyunsaturated fats like linoleic acid have multiple double bonds. These double bonds are easy to break and when they are broken they form free radicals that must find electrons to pair with. These oxidized products of linoleic metabolism (OXLAMs) go by the names 4-HNE, 9 and 13 HODE, DiHOMEs, etc. These oxidized molecules are then capable of damaging nearby structures. This means that mechanistically, it’s possible that linoleic acid could potentially cause damage. Additionally, linoleic acid is the precursor to arachadonic acid, which is responsible for generating inflammatory signals in the body. So this is another plausible mechanism of them causing harm. This is in no way a smoking gun, but the potential is there.
Then you look at in vitro studies (ie. done in a petri dish) to see if these oils could be problematic. What you will find that decrease immune cell function, damages cells in your eyes and pancreas, damages your cholesterol, and many other cells in the human body.¬†You put pretty much any cell in a dish with these oils and their function will decline, but humans aren’t petri dishes, I know. So what do the human or animal studies show?
First, there are two randomized controlled trials, the Minnesota Coronary and Syndey Diet Heart Study, that both showed corn oil (vegetable oil) increased the risk of heart attacks, strokes, and cardiovascular death. Interestingly, the results of these studies were hidden from the public for decades as they didn’t go along with the narrative. On top of this there are many animal studies that show this oil increases obesity, atherosclerosis, alterations in brain development, insulin resistance, and many other negative health outcomes. In humans, we know that the driver of heart disease is oxidized cholesterol. How does cholesterol oxidize? Heating or digesting linoleic acid is the predominant way that this happens. There have been studies looking at the quality of LDL cholesterol and they show that these oils damage your LDL cholesterol (aka oxidize it), which is a key step in atherogenesis, or the development of arterial plaque. Saturated fats, for as much as they are demonized, are not oxidizable so there role in atherosclerosis is really just a bunch of handwaving.
Now you are probably wondering what oil you should use to cook with. The oils I prefer are tallow, butter, and ghee as they are animal fats that are very low in these toxic oils. Everyone seems to be using olive and avocado oil (fruit oils) these days and these are much better than seed oils, but they still contain substantial amounts of linoleic acid. Olive oil ranges pretty dramatically from 12% (high quality) to 27% (low quality), which is too large of a range for me to want to mess around with. Cultured oil is another option, which is essentially oil produced from bacterial fermentation. It is exceptionally low in linoleic acid and is a good option for salads and things where you would typically use olive oil.
Getting rid of these oils and checking labs that examine the effects of these oils in the body are some of the first things that I do with my patients. I also explain that it takes 3.5 years to get these fats out of your system, so your health isn’t going to improve overnight. Starting to get educated on the sources, alternatives, and how to mitigate their damaging effects are the first steps. Good luck!

Sources: Zero Acre Farms Blog