If you're in one of those municipalities that would rather ban foods than learn science, you probably aren't allowed to have food with trans fats in a restaurant.

That's because, they say, trans fat lowers “good” HDL cholesterol and raises the “bad” LDL variety - but that's not true for the kind normally present in meat and dairy products and those are 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 also. 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.

The dairy industry wants the natural trans fat in its products excluded from the rules for labeling trans fat, so the results from these studies help make their case—and warrant some healthy skepticism, as do many industry-sponsored investigations. On the other hand, there are other reasons to believe that natural trans fat is less harmful than the artificial version.