Seed oils. What are they and are they bad for you?

Almost everything contains industrial seed oils, also called vegetable oils. If you use cooking oils, eat pre-packaged foods, or dine out at most restaurants, you’re probably consuming them daily. Global vegetable oil production has increased more than 16-fold since 1909, has doubled in the last 20 years, and is expected to grow by 30% in the next four years. The consumption of soybean oil alone has grown 1,000-fold since 1909 in the United States. Increased vegetable oil consumption correlates with higher rates of modern health problems like obesity, heart disease, cancer, and diabetes. Many have described seed oils as “toxic,” and scientific evidence suggests that seed oils have toxic effects on cells, animals, and humans. In this article, we will examine seed oil toxicity and clarify the safety of seed oils by exploring different studies.

Vegetable oils refer to oils or fats derived from crops, including fruits, grains, nuts, and seeds, while seed oils are derived specifically from seeds. Seed oils are refined from the seeds of crops, often using industrial methods like solvents, high heat, and large amounts of mechanical pressure. The most common examples of industrial seed oils are canola (rapeseed) oil, corn oil, cottonseed oil, grapeseed oil, peanut oil, rice bran oil, safflower oil, soybean oil, and sunflower oil. Seed oils are high in an omega-6 polyunsaturated fatty acid (PUFA) called linoleic acid, which contributes to general inflammation and health issues when eaten in excess. In 2017, people living in industrialized countries consumed 20% or more of their calories from seed oils high in linoleic acid, reflecting a 20-fold increase in seed oil consumption in the past 100-120 years.

Seed oils also contain fats that are oxidized or structurally damaged at the molecular level due to industrial processing, storage, or when heated and used for cooking. Oxidation makes the biological effects of seed oils significantly more harmful than other fat sources that aren’t as easily oxidized. This article discusses seed oils for the purposes of toxicity and does not include olive oil, avocado oil, or coconut oil, which have low to moderate amounts of linoleic acid. “Toxic” is an appropriate word to describe high linoleic seed oils, especially when heated and consumed in the amounts most people consume them today. Toxicity is dependent on the amount and concentration of a substance taken over time. Therefore, seed oils are toxic because they are consumed regularly and increase the risk of chronic diseases like heart disease, stroke, cancer, and diabetes.

High levels of linoleic acid and low levels of oleic acid increased the rates of LDL oxidation, according to a 2006 cell study comparing the toxicity of different fatty acids to RINm5f cells. A 2010 study examining the effects of linoleic acid on bovine oocytes found that the omega-6 fat hindered the maturation of the cells and hindered early embryo development. Animal studies have shown that oxidized linoleic acid byproducts led to increased oxidative stress, larger cardiovascular lesions, lower levels of liver ppar-alpha, and lower plasma levels of HDL. In a study on young piglets, the group that consumed high amounts of linoleic acid had impaired and altered neurological development compared to the group with required amounts of linoleic acid to prevent deficiency. In mice predisposed to Alzheimer’s disease, increasing linoleic acid intake led to impairments in working memory, brain structure, and more beta-amyloid plaque development compared to the control group. Animal studies have shown that high levels of linoleic acid consumption may promote obesity, insulin resistance, and reduced activity, all of which contribute to the obesity epidemic.

Increased vegetable oil consumption is found to be highly dangerous, next to heavy smoking and severe obesity, according to recent studies. These studies aimed to demonstrate the benefits of seed oil consumption, rather than investigating the potential harm of a high linoleic acid diet. If objective, balanced safety research on dietary linoleic acid from seed oils had been conducted and published in the 1960s and 1970s, present-day health statistics might have been different. Unfortunately, the 1960s study conducted by the American Heart Association on over 800 veterans had several flaws, including the increased rate of death by cancer documented in the experimental group. Cooking oils with high smoke points are important to use because burnt oils increase oxidized byproducts that are associated with inflammation, cancer, and heart disease. Cooking fumes are harmful to breathe in, mainly containing polycyclic aromatic hydrocarbons (PAHs) and aldehydes, both of which are carcinogenic and higher in PUFAs compared to other forms of fat. The rise in popularity of seed oils was due to the belief that they were good for health, which has now been disproven by several studies that have shown the potential harm of seed oils. The reduction in LDL or total cholesterol does not necessarily translate to a reduced risk of cardiovascular disease and mortality.