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Trans fats, also called partially hydrogenated oils, were created by chemists to replace butter and other saturated fats when saturated fat was first linked to heart disease.

But it turned out that trans fatty acids have proven even worse for health than saturated fat. In addition to raising your LDL ("bad") cholesterol levels, trans fats -- like saturated fats -- also decrease your HDL ("good" ) cholesterol levels at the same time. According to the American Heart Association, eating trans fats increases your risk of developing not only heart disease but also stroke and type 2 diabetes.

In 2006, the FDA began requiring most food companies to include trans fat grams on the Nutrition Facts label, just below saturated fat.

Since this nutrition label change, the amount of trans fat in our food has declined remarkably, according to the Center for Science in the Public Interest, which first raised the trans fat alarm. Most food manufacturers are gradually phasing out trans fats products or at least reducing the amount of trans fat used in food production.

Still, it's far too easy to eat more than the recommended limit of trans fats each day: 2 grams in a 2,000-calorie diet or less than 1% of your total daily calories.

Food labels can claim to be "trans-fat free" or have "0 trans fats" if they contain half a gram of trans fat or less per serving. Yet if you eat four servings of that food, you've reached your daily limit. Trans fats also occur naturally in very low levels in meat and dairy products, but the vast majority of trans fat in our diet comes from packaged food.

Where Are Trans Fats Today?

Today, many food manufacturers have eliminated or hugely reduced the amount of trans fat in their products. You can buy cookies and soft-spread margarine with zero or little trans fat. In fact, for every product at the supermarket that contains trans fats, you can probably find a "0 trans fat" alternative if you read labels carefully. Be warned, however, that the current labeling law allows products to claim zero trans fats if they contain less than 0.5 grams per serving. Still, even today, trans fats are used by some food makers -- and certain products are more likely to contain trans fats. The Center for Science in the Public Interest in 2007 conducted a limited supermarket survey and found a day's worth of trans fat in various brands of:

  • Pot pies
  • Microwave popcorn
  • Frozen pizzas
  • Pastries
  • Cookies
  • Convenience foods

What should consumers do? Shop smart. Read labels and buy products with the smallest amount of trans fat and saturated fat. Check the ingredient listing and if the words ‘partially hydrogenated’ are listed, the product contains trans fats. But switching from trans fats to butter won't do your heart any good.

Shopping for healthy fats is far easier in the grocery store -- where fat facts appear on labels --than in fast-food restaurants. Here are some tips for avoiding trans fats in fast food.