Harvard Health Letter

In Brief: Trans fat, au naturel

In Brief

Trans fat, au naturel

Trans fat is a certifiable nutritional bad guy. It lowers "good" HDL cholesterol and raises the "bad" LDL variety. Boston, once infamous for banning books, has now joined New York City and other municipalities by banning trans fat from its restaurants. Many food makers have stopped using trans fat as an ingredient, for public health and PR reasons.

But there's some "natural" trans fat in meat and dairy products that these bans won't touch. Should we be worried about it? Probably not.

Artificial trans fat is made when a vegetable oil is converted into a solid through the process called partial hydrogenation, which sticks hydrogen atoms on oil molecules' fatty tails. But the addition of hydrogen, or hydrogenation, occurs in nature, too. Bacteria in animals' stomachs hydrogenate the fatty oils from animal feed, for example. Definite numbers are hard to come by, but a cup of whole milk may have about 0.24 grams of trans fat and a quarter pound of hamburger about 0.8 grams. That pales in comparison to the five or so grams contained in a single doughnut.

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