The truth about trans: hydrogenated oils aren't guilty as charged - trans fats

Nutrition Action Healthletter, March, 1988 by Elaine Blume

But Edward Emken, a biochemist with the Department of Agriculture's Agricultural Research Service in Peoria, Illinois, notes that the body selectively excludes trans fats from key membrande positions. [1] "Trans fats are only incorporated into these positions when an animal is fed so much trans fat that it has no other choice," he explains. "But those dietary levels are unrealistically high."

According to Emken, charges that trans fats impair the immune system are based on inadequate data. "There's no hard evidence to suggest that, at current levels of intake, trans fats pose any more danger than other kinds of fat," he maintains.

Although trans fats don't present a clear-cut threat, it makes sense to avoid excesses. "Humans have been consuming trans fats for eons," explains John Kinsella, a food chemist at Cornell University, "but only in very limited amounts. As long as you are not flooding the system wiht them, it's probably all right."

Kinsella believes an excess of trans fats in the diet may increase the body's need for linoleic acid, a fatty acid called "essential" because it must come from the diet. (That is, the body can't make its own.) However, because linoleic acid is found in soybean, safflower, corn, and other polyunsaturated vegetable oils, we get a more-than-adequate supply of this nutrient. In fact, some studies suggest that our generous linoleic acid intake actually promotes cancer.

All told, the charges against trans fat just don't stand up. And by extension, hydrogenated oils seem relatively innocent.

Although hydrogenation can be used to make fats completely saturated, it is rarely used that way. In ordinary "partial hydrogenation," most of the change is from polyunsaturated to cis and trans monounsaturated fats, with relatively little saturated fat produced. Soybean oil, for example, starts out 15 percent saturated, but after hydrogenation to make margarine, it ends up about 17 to 20 percent saturated fat. [12,13]

That means margarine is much less saturated than butter, which is 66 percent saturated. In addition, the kind of saturated fat (stearic acid) produced by hydrogenation does not seem to raise blood cholesterol as much as other saturated fats. [14]

In countries where heart disease is rampant, that makes margarine preferable to butter. True, if you cut back on saturated fats in meat, cheese, and pastries, and don't have high blood cholesterol, you can probably afford an occasional pat of butter on your toast. But that's a matter of taste, not health.

As for processed foods, you're better off choosing products made with hydrogenated soybean, corn, or cottonseed oil than those containing butter, lard, beef fat, or palm, palm kernel, or coconut oil. But you're even better off cutting back on total fat. That may reduce your risk of cancer and heart disease and should help keep your waistline within reasonable limits. And it will make concern over trans fats the small issue it should be.

References

[1] Ann. Rev. Nutr. 4: 339, 1984.