Yes, soybean oil can be considered a healthy oil, provided that it's not been hydrogenated and provided that it's certified organic. All plant oils have different nutrient profiles, including the types of fat they contain. The plant oil that best fits into your diet depends largely on the type of fat that's missing from the rest of your diet as a whole and that's best matched to your cooking needs. Soy oil would be especially helpful for a diet that was missing the essential omega-6 fatty acid called linoleic acid. (Soy oil is about 50% linoleic acid). It would also be helpful for a diet that needed more monounsaturated fat (soy oil is approximately 25% monounsaturated).
Let's compare this soy oil profile with the profiles of two other commonly chosen oils. Almost three-quarters of the total fat of olive oil are monounsaturated fat (in the form of one particular fatty acid called oleic acid). Olive oil also contains about 10% linoleic acid and a very small amount of linolenic acid, an omega-3 fatty acid. For one more comparison, consider canola oil. This oil's fatty acid profile features approximately 60% monounsaturated fats, 20% linoleic acid, and about 10% linolenic acid.
In practical terms, what does all of this information tell us about which oil to select? In and of itself, it doesn't really provide us with any good answers! That's because we first have to match it with our health and cooking needs.
Most U.S. adults get a sufficient amount of linoleic acid from their overall diet (we average about 13 grams per day), making this omega-6 fatty acid less likely to be needed from either soy oil or canola oil. There are some individuals, however, who would definitely benefit from increased intake of linoleic acid in their Healthiest Way of Eating. For the most part, however, it's not linoleic acid that we are missing, but linolenic acid (that key omega-3 fatty acid). From this standpoint, canola oil would be the best choice from among the three oils described above because it contains the greatest amount of linolenic acid.
From a cooking standpoint, however, oils containing polyunsaturated fats (like omega-3 or omega-6 fats) are generally less stable and more susceptible to cooking damage. From the cooking standpoint, the high monounsaturated content of olive oil would make it the least likely of the three oils to be damaged by low heats.
In my book, olive oil is the only plant oil that I include as one of the World's Healthiest Foods. I did not make this decision based on its fat profile, however, but rather upon its unique phytonutrient profile. Olive oil and olives contain a variety of polyphenols that have repeatedly been shown to have rich health benefits. If you've surveyed the book, you'll already know that I don't like to heat any oil due to the risk of heat damaging delicate fats. With olive oil this principle is doubly important because of this rich mix of polyphenols.
The bottom line with soy oil—and with all components of your diet—is that it is important to determine what's best matched for your individual health needs and cooking plan and then insisting on the highest quality food to meet those needs.
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