Trans fat lowers "good" HDL cholesterol and raises the "bad" LDL variety. Some municipalities have responded by banning trans fat from restaurants and many food makers have stopped using trans fat as an ingredient. But there's some trans fat normally present in meat and dairy products that these bans won't touch. Fortunately, this "natural" trans fat is not a big health concern, reports the July 2008 issue of the Harvard Health Letter.
Hydrogenation — the process used to convert oil into solid trans fat by adding hydrogen—occurs in nature, too. Bacteria in animals' stomachs hydrogenate the fatty oils from animal feed, for example.
Two dairy industry–funded studies published in the March 2008 issue of The American Journal of Clinical Nutrition compared the effects of artificial and natural trans fat. One study found that eating artificial trans fat lowered HDL in the women studied, while natural trans fat increased HDL. There was no difference in how the two different types of trans fat affected men. The other study found that large amounts (3.7% of calories) of either natural or artificial trans fat produced similarly bad effects on heart disease risk factors. Relatively small amounts (1.5% or 0.8% of calories) of natural trans fat didn't have an effect.
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