Years ago, I attended a seminar on food-based holistic health which included a segment very quickly running through some of the speaker’s views on the different cooking oils that are on the market. For several years now, my own personal oil use has been more or less restricted to the occasional olive oil in a cast iron skillet to cook a stir fry, so I didn’t pay as close attention as I perhaps should have.
It wasn’t until a client of mine brought up eliminating oils from his diet that I decided to give the topic a deeper look. From what I can tell, as with many health-related subjects, there is a range of perspectives often regarding the same health indicators.
Holistic nutrition, while a passion of mine, is not yet something in which I am professionally trained. So, with that in mind, I’ll leave the conclusions for my readers to draw. Here below though, I’ve collected five studies I’ve found specifically on linoleic acid, a polyunsaturated fatty acid in our vegetable and seed oils (think: corn, soybean, canola, sunflower, pumpkin seed, etc).
Linoleic acid seems often to be identified as the villain in these oils, however, more recent research (included below) suggests it may be more complicated than that. What do you think?
In this 2004 study published in the European Journal of Endocrinology, researchers found that people who used olive oil for cooking alone experienced lower insulin resistance than those who used sunflower oil or a mix of the two. Insulin resistance positively correlated with oleic acid (higher in olive oil) and negatively with linoleic acid (higher in sunflower oil).
Essentially what this study observes is that the risk of higher insulin resistance-that is, the body’s failure to respond normally to insulin-was lower in people who cooked with olive oil compared to sunflower oil.
Much more recently, a team of researchers with the National Institutes of Health and the University of North Carolina at Chapel Hill found a 30–40% reduction in headache hours per day, severe headache hours per day, and overall headache days per month for sufferers of migraines who consumed higher levels of fatty fish and lower levels of vegetable oils (high in linoleic acid).
Importantly, this research adds to a growing body of studies demonstrating the impact of dietary changes on chronic pain. In a backhanded way, it also sheds light on the un-helpfulness of the American diet in relation to chronic pain such as migraines, given that the study group given a diet high in vegetable oils and low in fatty fish was meant to mirror the average American intake.
Research by scientists at the University of California, Riverside in 2015 found that soybean oil causes higher rates of obesity and diabetes than fructose (the much-maligned sugar found in soda and many highly processed foods).
Mice in the study fed the high soybean oil diet were observed to experience “increased weight gain, larger fat deposits, a fatty liver with signs of injury, diabetes and insulin resistance, all of which are part of metabolic syndrome.”
This article is less of a study and more an analysis of many different studies into the nutritional value of linoleic acid. It notes the complexity of research into linoleic acid’s impact on cardiovascular health, while also documenting the compelling connections between linoleic acid and cancer.
For instance, the article notes that “under some conditions linoleic acid can act as a promoter of tumor growth.” It also identifies connections to mammary cancer, increased incidence of cancer and cancer mortality, and “correlative data that support the idea that increases in the incidence of some cancers mirror the increase in linoleic acid consumption.”
Lastly, this new study by researchers at UC Riverside links soybean oil not just to the increased rates of obesity and diabetes as noted in the team’s 2015 study included above, but also to decreased oxytocin levels and to genetic malfunctioning which may exemplify the oil’s impact on neurological conditions including autism and Parkinson’s.
As I mentioned in the introduction, recent research complicates the idea that linoleic acid alone is responsible for these effects. In a 2017 study, the UC Riverside team showed that genetically engineering soybean oil to be lower in linoleic acid also lowered rates of obesity and insulin resistance. Nevertheless, in this study, both natural and genetically modified soybean oil showed genetic disruptions, suggesting they are not caused by linoleic acid.