December 15, 2017
Understanding Vegetable Oils

Understanding Vegetable Oils

by Edward R. Blonz, Ph.D.  

Most vegetable oils are heart-healthy when they replace foods high in saturated fats in an otherwise well-balanced diet. But there are differences between them in their composition and cooking properties. Here's a brief look.

All vegetable oils are pure fat and, like all fats, are combinations of saturated, monounsaturated, and polyunsaturated fatty acids—though they are typically categorized according to their predominant type. For instance, olive and canola oil are high in monounsaturated fats, while soybean and corn oil are high in polyunsaturates. Vegetable oils provide about about 13 grams of fat and 120 calories per tablespoon and, like all plant foods, have no cholesterol.

For frying or stir-frying, choose an oil with a high “smoke point”—that is, it will tolerate high temperatures before breaking down and releasing a harsh smell and smoke into the air. The more refined the oil, the higher its smoke point: Corn, soy, grapeseed, safflower, and refined avocado oils all have high smoke points.

Expensive extra-virgin olive oil also tends to have a higher smoke point—but its delicate taste is destroyed by the heat. If you want to use olive oil for high-heat cooking, opt for a more refined (and cheaper) “light” olive oil. For extra flavor in cooking and in salad dressings, experiment with specialty oils, like avocado, almond, grapeseed, hazelnut and walnut oil.

All cooking oils will eventually turn rancid if stored at room temperature (especially kitchen temperature). Buy a small dispenser bottle or can and keep enough oil in it for daily use; store the rest of the bottle in the refrigerator. It will congeal in the refrigerator, but will liquefy again after a few minutes at room temperature.

Vegetable oils by fat content

(Listed according to saturated fat content, from lowest to highest. Serving size is 1 tablespoon.)

Oil Saturated Fat (Grams) Polyunsaturated Fat (Grams) Monounsaturated Fat (Grams)
Safflower 0.8 2.0 10.2
Canola+ 0.9 4.1 8.0
Hazelnut 1.0 1.4 10.6
Walnut+ 1.2 8.6 3.1
Flaxseed++ 1.3 10.2 2.5
Grapeseed 1.3 9.5 2.2
Sunflower 1.4 8.9 2.7
Avocado 1.6 1.9 9.9
Corn 1.7 8.0 3.3
Olive 1.8 1.2 10.0
Sesame 1.9 5.6 5.4
Soybean 2.0 7.8 3.2
Peanut 2.3 4.3 6.2
Cottonseed 3.5 7.0 7.0

++ Excellent source of ALA

+ Good source of alpha-linolenic acid (ALA), an omega-3 fatty acid

Also see How to Buy Spreads.