Murder by French Fry

When health concerns developed over the use of saturated animal oils in french fries, the fast food industry changed its cooking oil. They switched to a polyunsaturated vegetable oil. That was good. But in treating that unsaturated oil to make it better for frying, they ended up with trans fats. That was bad.

A young girl eats some fries.
Peter Cade/Iconica/Getty Images
Trans fats aren't as rampant as they were a few years ago, but their ability to accumulate over a lifetime still makes them dangerous.

­The term "saturated" doesn't refer to how densely fatty something is. It refers to the amount of hydrogen in a fat molecule.

A fat molecule is made up of carbon, hydrogen and oxygen. When all of the open slots in the molecule are filled with hydrogen ("hydrogenated"), that fat is hydrogen saturated, or just "saturated." Hydrogenation makes oil a solid at room temperature, as in margarine, and keeps it from going bad so quickly on store shelves. Whether a fat is "saturated" or "trans" refers mostly to the arrangement of those carbon and hydrogen atoms. The placement of hydrogen atoms in saturated fats makes the molecules bend; the placement in trans fats keep them straight. That's the big chemical difference. The health difference is much bigger.

Saturated fat molecules, found in foods like beef, butter and doughnuts, tend to increase bad cholesterol and decrease good cholesterol. Trans fats do the same, but worse. A study of 80,000 women showed that a 5 percent increase in daily calories from saturated fat can increase the risk of heart disease by 17 percent. That same study found that a 2 percent increase in trans fat can increase the risk of heart disease in women by more than 93 percent (in men, that number is closer to 25 percent) [source: Straight Dope]. Another study found that high intake of trans fat increases the risk of death by heart attack by 47 percent [source: AICR]. The USDA recommends limiting trans fat intake to 1 percent of your daily calorie intake. So if you eat 2,000 calories a day, you should only consume 20 calories of trans fat, which is about 2 grams. So check nutrition labels -- as of 2006, food manufacturers have to put the amount of trans fat on their packaging.

Now, lots of commercial foods contain trans fats. Why the focus on french fries, then? Until recently, here's why [source: U.S. FDA]:

Food (one serving)

Trans Fat Content

Stick of margarine

3 grams

Potato chips

3 grams

Shortening

4 grams

Doughnut

5 grams

French fries

8 grams

Not long ago, eating a single serving of fast food french fries got you more than four times your daily healthy allotment of trans fats. These days, major fast food chains don't use trans fats because of health concerns. Unfortunately, fats can start building in the arteries from the preteen years, so we're not exactly out of the woods [source: WebMD].

Which brings us back to our initial question: Which is deadlier, french fries or car accidents? We're far more likely to die from overconsumption of trans fat. In the United States, people have a one-in-84 chance of dying in a car accident, and one-in-five chance of dying from heart disease. That's greater than the risk of dying from cancer, which is one-in-seven [source: NYT].

One the upside, Americans only have a 1-in-340,733 chance of dying in a fireworks accident. Fireworks displays are a fine replacement for sticks of butter [source: NYT].

For more information on heart disease, diet and trans fats, including how trans fats might increase infertility in women, check out the links on the next page.