Trans fats are the Frankenstein's monsters of the fat world. They're what happens when you pump hydrogen into an oil to make it solid. Trans fat consumption gained a foothold during World War II, when margarine was adopted as a substitute for butter. Subsequently, manufacturers used hydrogenation to turn cheap, subsidized soy oil into cheap, shelf-stable shortening for cookies, crackers, and snack foods - and to feed the fryer at the local fast food joint.

Initially, hydrogenated oils appeared to be healthier than saturated animal fats (think butter, lard, schmaltz), which were known to raise blood cholesterol levels. But research has shown that, while saturated fats are bad, trans fats can be monsters. These abnormal fats raise blood cholesterol, specifically LDL, or bad, cholesterol.

The FDA required trans fat labeling beginning in 2006. Since then, we've seen an explosion of foods bearing the label "trans fat free." But a product can be trans fat free and still have a significant amount of total fat, increasing the risk of obesity, heart disease and cancer. In addition to looking for the words "trans fat" on food labels, also look for "partially hydrogenated oil."

Two unfortunate twists: As a substitute for hydrogenated soy oil, manufacturers have turned to palm oil, one of the few vegetable fats that's solid.

Unfortunately, palm oil is wickedly effective at raising blood cholesterol.

Also, trace levels of trans fat occur naturally in butter. Research indicates that these natural trans fats might actually be good for us, but in the frenzy to rid the world of trans fats, some high-quality bakeries have been forced to swap their butter for unnatural alternatives.

Pommes Frites

4 small russet potatoes

2 tablespoons, plus 1/4 teaspoon, olive oil, divided

• Cooking spray

2 teaspoons minced fresh rosemary

1 teaspoon kosher salt

Preheat oven to 450F.

Peel potatoes and cut into 1/4-inch wide strips. Blot dry with paper towels. Lightly coat a large baking sheet with cooking spray. Toss potatoes with 2 tablespoons olive oil; spread in a single layer on baking sheet. Bake 35 to 40 minutes, until potatoes are golden and crisp.

Warm rosemary with 1/4 teaspoon olive oil in a nonstick skillet. Toss with potatoes in a bowl. Sprinkle with salt. Serves 6.

Per serving: 130 calories, 5g fat, 0mg cholesterol, 2g protein, 20g carbohydrates, 1g fiber, 330mg sodium.

Look for Relish magazine, celebrating America's love of food, each month in the Gazette-Times. For more Relish recipes, see www.relishmag.com.