Vegetable oils. Found in recipes from baking to stir-fry and listed on labels from granola bars to body lotion. What are these oils? Which should you include in your diet and which should be avoided? Let’s find out.
Simply put, vegetable oil is a fatty oil extracted from a seed or fruit (1). The most common vegetable oils you’ll find on the market today are avocado, coconut, corn, olive, peanut, rapeseed, soybean, safflower, sunflower and canola.
Oh, the beautiful sight and smell of the canola…flower? plant? Wait, what is a canola? We'll get to that in a bit, but let’s first discuss how a seed or fruit is turned into an oil.
Oil quality is determined by purity of the origin plant as well as the method in which it's processed. Meaning, some oils are organic, pure and unrefined, while others are genetically modified and highly processed. (Hint — the former is healthy, the latter is not!)
All extraction begins the same, where the seed or fruit undergoes a phase of cracking, crushing, or grinding (2). From there, the meal is pulverized and then either pressed or processed. This step is a major step in determining whether the resulting oil will be healthful or harmful. Let’s break it down:
The best option is cold-pressed. Cold pressing is done through the ancient practice of grinding and milling or the modern practice of a slow, hydraulic press (3). This process will yield the most nutrient-dense product due to the low temperatures being used. Higher temperatures greatly reduce quality of the oil (4).
Your second best option is expeller-pressed. While these oils do undergo some refinement at slightly higher temperatures than cold-pressed, there are no chemicals used in the process, maintaining integrity of the resulting product.
Oils to be avoided are those that are chemically processed and refined, often at very high temperatures. Instead of a physical press, chemicals such as hexane (found in glue and leather cleaners) are used for oil extraction, followed by degumming, neutralization, dewaxing, bleaching, filtration and deodorization, and possible hydrogenation where the oil is re-bleached and re-deodorized (5). This process degrades the structure of the oil, resulting in a rancid and potentially toxic product.
Now you may be wondering, how will I know which oils are cold-pressed vs. expeller-pressed vs. chemically processed? Rest assured, any high-quality oil will have it’s process clearly listed on the label. Lower quality oils tend to leave this information out or utilize trickery via fancy marketing. Here is a quick cheat-sheet for your next purchase:
cold or expeller pressed
cold or expeller processed
Now, going back to canola. Derived from genetically modified rapeseed and highly processed, this oil is one you’ll want to avoid at all costs. Along with canola, you’ll want to avoid corn, rapeseed, and soybean as they all fall into the same category and are detrimental to our health.
Generally speaking, the preferred, unrefined and heart healthy vegetables oils are coconut, olive, peanut, safflower and sunflower. But buyer beware, some of these healthy oils do undergo refinement and chemical processing, which can destroy the oil’s beneficial properties (6). Use the nifty cheat-sheet above to choose the healthiest option!
Now that you’re confidently purchasing the very best oils for your health, ensure they stay fresh by storing them in the refrigerator (7)! The only exception here is olive oil, which should be kept in a dark place, such as the cupboard.
1 “Vegetable Oil.” Merriam-Webster, Merriam-Webster, www.merriam webster.com/dictionary/vegetable%20oil.
2 Know Your Fats: the Complete Primer for Understanding the Nutrition of Fats, Oils and Cholesterol, by Mary G. Enig, Bethesda Press, 2000, p. 148.
3 Broaddus, Hannah. “The Difference Between Solvent Expelled, Expeller Pressed and Cold Pressed Oil.” Non-GMO & Organic Oil Supplier & Packer, 17 July 2017, www.centrafoods.com/blog/the-difference-between-solvent-expelled-expeller-pressed-and-cold-pressed-oil.
4 Sionek, B. “Cold Pressed Oils.” Roczniki Panstwowego Zakladu Higieny, U.S. National Library of Medicine, 1997, www.ncbi.nlm.nih.gov/pubmed/9432706.
5 Know Your Fats, p. 9.
6 Axe, Josh. “Coconut Oil: 20 Health Benefits, Nutrition and Popular Uses.” Dr. Axe, 24 Apr. 2019, draxe.com/coconut-oil-benefits/.
7 Staying Healthy with Nutrition the Complete Guide to Diet and Nutritional Medicine, by Elson M. Haas and Buck Levin, Celestial Arts, 2006, p. 529.