First it was cholesterol, then saturated fat. Now trans fatty acids are the latest dietary demon. Like those nutrients, trans fats raise blood cholesterol levels and significantly increase the risk of premature heart disease.

Trans fat has been nicknamed "phantom fat" because the Food and Drug Administration does not require it to be listed on food labels. As a result, even health-conscious consumers are often unaware that hundreds of popular foods -- from margarine, baked crackers and biscuits to cookies, fish sticks and french fries -- pack significant amounts of trans fatty acids. Much of this fat comes from liquid vegetable oils that have been converted to solids because they stay fresh longer than conventional shortenings.

On average, Americans consume about five grams of trans fat per day, accounting for about 3 percent of their total calories, according to a 1999 study in the Journal of the American Dietetic Association.

While that may sound tiny, research has linked even small amounts of trans fat to an increased risk of heart disease. A 1994 Harvard University study found more than twice the risk of heart attacks among those who ate partially hydrogenated oils, which are high in trans fat, compared with those who consumed little trans fat. Several large studies in the United States and elsewhere, including the Nurses Health Study, also show a strong link between premature death and consumption of foods high in trans fatty acids.

"Trans fats are unique in that they affect blood lipids in every way that is harmful," said Walter C. Willett, chairman of nutrition at the Harvard School of Public Health in Boston.

This hidden fat raises low-density lipoprotein (LDL)--the harmful form of cholesterol--and lowers protective high-density lipoprotein (HDL)--the so-called "good cholesterol." To some, including Harvard's Willett, the combination makes trans fatty acids "much worse than saturated fat."

Yet, most Americans are clueless about the dangers of trans fat. A 1995 survey by the FDA found that 90 percent of those polled were either unaware of the risks of trans fat or mistakenly thought that it was beneficial.

Even those who recognize trans fat as something to avoid are often confused about how best to do that. "I know they're bad for you," said grocery shopper Stanley Gorinson at the Westbard Giant in Bethesda recently. "But no, I don't know what foods they're in."

Many Americans are still struggling to sort out the health effects of saturated, polyunsaturated and mono-unsaturated fat. Butter and other whole milk dairy products, as well as meat, poultry and other animal products contain saturated fat, which raises the risk of heart disease. Corn oil and safflower oil are rich in polyunsaturated fats, while olive and peanut oils contain mono-unsaturated fats. Research has shown that these types of fat do not promote heart disease. And studies suggest that in some cases these fats may help lower risks.

Those who try to reduce trans fat will find it tough because most food labels "don't have the information that you need to do that," said Margo Wootan, senior scientist at the Center for Science in the Public Interest (CSPI), a consumer advocacy group that has led the charge since 1993 to get trans fat listed on dietary labels. Nutritional labels on prepared foods list the total grams of fat in products and that total does include trans fat, but there is no separate line showing, as they do with saturated fats, the actual amount of trans fats.

The FDA, however, proposed in November that food manufacturers begin including trans fat on labels. The 90-day public comment period won't end until mid-February and two food companies have already requested a 90-day extension, according to Virginia Wilkening, acting director of the FDA's Office of Food Labeling. When the comment period ends, it could take about two years for any new rule to go into effect.

Under the proposed regulation, trans fat would be folded into the saturated fat gram count, since both raise the risk of heart disease. An asterisk would direct the consumers to the bottom of the label where they could find a reference listing the exact amount of trans fat included in the food.

If the proposal goes forward, trans fat would also be part of the nutritional information that the FDA considers when it gives foods such rankings as "lean," "extra lean," "reduced saturated fat" or "low saturated fat." Low-cholesterol foods that now sometimes contain significant amounts of trans fatty acid would be required to contain less than two grams of saturated fat and trans fat per serving combined.

The FDA estimates that these labeling changes would prompt changes in eating habits that would save at least $1 billion in annual health care costs by preventing 6,400 cases of heart disease per year and at least 2,100 deaths.

Others say the benefits could be even greater. "Trans fatty acids are responsible for about 30,000 premature deaths per year," said Harvard's Willett. "The FDA's numbers were based on small reductions in trans fat, but they didn't make the assumption that people would fully avoid them. That's not hard to do if one has the information and it's something that consumers really need to consider if they are trying to make the healthiest choices for their diets . . . . It's why the FDA change is so important."

The Stealth Fat

Why the sudden concern about trans fats?

Beef and high-fat dairy products have always contained minuscule amounts of trans fat, which is produced in the gastrointestinal lining of cattle. But in the 20th century food manufacturers discovered the stability and long shelf life of trans fat. During the past 50 years, trans fat has become one of the most common ingredients in both grocery store food and restaurant fare. [See "FDA Plan for Trans Fatty Acids Doesn't Cover Fast Foods," Page 14.]

Trans fats are produced when food manufacturers take liquid vegetable oils, heat them and add metal catalysts and hydrogen to the mix. Called partial hydrogenation, this process produces hardened vegetable oils that remain solid at room temperature. They can then be made into shortening and margarine and are less likely to spoil.

With the proliferation of prepared foods in recent years, it's a small wonder that a long and varied list of products now contains hidden trans fat. Food surveys suggest that the typical American eats about 34 grams a day of saturated and trans fat combined, well over the recommended daily intake of 20 grams of saturated fat for an average 2,000 calorie-a-day diet.

A close look shows clearly how the numbers creep up. Think that biscuit with three grams of saturated fat on the label isn't too bad? Add in the four grams of trans fatty acid and it jumps to seven grams of artery-clogging fat.

Peruse the label of those chocolate chip cookies that boast only two grams of saturated fat per serving. Surprise! They contain double the amount of fat when the trans fat is taken into account. Ditto for the fish sticks, which tout just three grams of saturated fat per serving but actually pack another five grams of hidden trans fat. Same goes for some of the most popular brands of baked crackers, which boast just one gram of saturated fat on their labels but contain an extra two grams of trans fat.

And that piece of apple pie? It has seven grams of saturated fat in the crust, but contains another seven grams of trans fat per serving.

In the dairy case, there's more confusion between butter and margarine. Butter contains no trans fatty acids--the reason that Karen Sandler of Bethesda serves butter instead of margarine to her family. "I know that trans fatty acids are something that you should never eat," Sandler said as she shopped recently.

But it's not that simple. Each tablespoon of butter still has seven grams of saturated fat--or roughly a third of the recommended daily intake. Many margarines--particularly stick margarines--are low in saturated fat, providing just two to three grams per tablespoon, but they come loaded with trans fat, sometimes as much as three additional grams per tablespoon.

"Labeling trans fat in foods may help to clear up this butter-versus-margarine controversy," said the CSPI's Wootan. "Stick margarines are almost as bad as butter, but the tub margarines are much better and the lower-fat tub margarines are much, much better."

The lack of consumer understanding and general nutritional confusion among the public about trans fats "is the major reason that we chose to propose the option that we did," said the FDA's Wilkening.

Until a final rule is made, however, consumers can only guess how much trans fat most foods contain. The easiest way to check is usually to read the ingredient list. If partially hydrogenated oils or fats appear, the food has trans fat. But knowing how much is difficult--unless the label happens to list mono-unsaturated and polyunsaturated fat grams, which are not required but are sometimes included on the label. Even then, consumers need to calculate the amount of trans fat by adding grams of polyunsaturated, mono-unsaturated and saturated fat and subtracting that sum from the total fat listed on the label. The difference is a ballpark estimate of trans fat. For example, Oreos have seven grams of total fat in a serving. The saturated fat, polyunsaturated and mono-unsaturated fat add up to five grams. The difference is two grams, and most of that is trans fat. Wheat Thins have six grams of total fat and only three grams are accounted for in the saturated, polyunsaturated and monounsaturated fat counts. That leaves three grams of fat and most of that is trans fat.

Educating the Consumer

By highlighting trans fatty acids on food labels along with saturated fat, the FDA hopes that it will also encourage Americans to vote with their shopping carts and avoid foods that are high in trans fat and saturated fat.

Miriam Bixler of Bethesda is one of those who welcome the proposed food label change. "It would be great to have the information," she said as she shopped recently for herself and her husband, who has an elevated blood cholesterol level. "I pay attention to trans fatty acids and try to make low-fat meals, low-cholesterol meals, but often can't find the information that I need."

Including trans fat on food labels is another way for the FDA to encourage food companies to alter ingredients, opting for more healthful alternatives. Some food manufacturers have already taken the hint. They have reformulated their products and are now capitalizing on that fact as a marketing tool.

Reaction to the proposed label change has generally been positive. The move has been endorsed by a wide variety of consumer and industry groups, from the American Heart Association to the National Association of Margarine Manufacturers.

But while lauding the proposal, some experts also worry that a trans fat phobia will grip the nation, much the way that consumers have recently demonized other ingredients, from cholesterol to sugar. "People should be aware of trans fat and saturated fat and limit them in their diets to help reduce the risk of heart disease," said Penny Kris-Etherton, a professor of nutrition at Pennsylvania State University. "But they also need to have a balanced perspective."

By focusing on only one ingredient, consumers run the risk of missing the nutritional forest for the trees. One of the most telling examples was the recent flirtation with nonfat foods. Many Americans mistakenly thought they could consume unlimited quantities of nonfat and low-fat products. "They forgot about everything else, including calories," Kris-Etherton said.

For now, the AHA and many public health officials recommend limiting total fat to 30 percent or less of total calories. That works out to about 600 calories in a daily diet of 2,000 calories.

The rule of thumb generally used by public health officials is that saturated fat and trans fat combined should make up no more than 8 to 10 percent of total calories, or about 160 to 200 calories daily, Kris-Etherton said. Polyunsaturated fat should hover around 10 percent of total daily calories--or about 200 calories per day, while mono-unsaturated fats, such as olive or canola oil could comprise the rest of the daily fat allowance, roughly 12 percent of total calories.

The bottom line is "to try to get saturated fat and trans fat as low as possible in your diet," Kris-Etherton advised.

To accomplish that, consumers will have to wait for the food labels to change. Claire Herne of Silver Spring is one of those who already skims ingredient lists and plans to pay attention to trans fatty acids when they are included in food labels.

"I know that partially hydrogenated trans fatty acids are bad," Herne said as she balanced her young daughter, Lydia, on her hip, while waiting in the checkout line at the Fresh Fields store in Tenleytown. "I use olive oil and I try to avoid tropical oils [with saturated fat] and beef tallow [which can contain both saturated and trans fat]."

More information would help, Herne said. "There's a lot of excess information on the labels that I don't understand and if I don't understand it, it's pointless," she said. "But if they can make the trans fatty acid labels pithy and explain enough, then it would be very positive."

FDA Plan for Trans Fatty Acids Doesn't Cover Fast Food

The Food and Drug Administration's proposal to require listing of trans fatty acids on foods has one loophole: It doesn't cover restaurants or fast food establishments.

Since a third of all meals are now consumed outside the home, many experts believe that the battle against hidden trans fat won't be over until eating establishments either divulge--or change--their ingredients.

"The numbers can be just unbelievable," said Margo Wootan, senior scientist at the Center for Science in the Public Interest (CSPI). "You see restaurant foods that can have five days' worth of artery-clogging trans fat and saturated fat in one serving. How do you make up for that even if you split it with a friend?"

Fast foods are some of the worst offenders, despite the fact that many fast food restaurants have switched to vegetable oils.

Fast food restaurants "advertise that their products are cooked in vegetable oil, but it is vegetable oil that is solid at room temperature and often very high in trans fat," said Walter C. Willett, chairman of nutrition at Harvard University's School of Public Health. "The information is not just missing, but also extremely misleading."

Burger King spokeswoman Kim Miller said that "we did shift to a partially hydrogenated vegetable shortening in 1989 for cooking french fries. In shifting away from animal shortening, we reduced the saturated fat by more than 50 percent and totally eliminated dietary cholesterol from the product."

Even so, a recent analysis of foods by CSPI still found a lot of fat. For example, a large order of fries at McDonald's had 19 grams of fat, including four grams each of saturated and trans fat. At Burger King, a king-size order of fries contains 30 grams of fat, 12 grams from saturated and four grams of trans fat, according to company-supplied nutritional data.

Choosing chicken at fast food restaurants doesn't help if it's fried. Nine chicken nuggets at McDonald's contains 25 grams of fat, including five grams of saturated fat, according to company-supplied information. CSPI found that it also contained three grams of trans fat. A fried chicken sandwich at Burger King has 43 grams of fat, including nine grams of saturated fat, according to Burger King. CSPI found that it also contained at least two grams of trans fat.

The proposed trans fat labeling rule wouldn't be mandatory for restaurants, but there's a small exception that may give consumers more information. Restaurants that make a health claim, such as saying that a food is heart-healthy or low-fat, "would need to give the amount of fat, including trans fat," said Virginia Wilkening, acting director of the FDA's Office of Food Labeling.

The same goes for food establishments that provide nutrition information, something a growing number of fast food franchises do, including McDonald's and Burger King. "Once we have the revised regulations in place, if restaurants choose to do nutrition labeling then they would need to include trans fat, too," Wilkening said.

Some fast food chains, including Burger King, are already making plans to label trans fat in their foods.

"The scientific and regulatory communities have not conclusively established the significance of trans fatty acids as it relates to elevated cholesterol levels since they make up such a small part of the dietary fat intake," Miller said. "However, it appears that we will be including trans fat in our nutrition guide sometime in the spring.

In the meantime, to help avoid trans fatty acids while eating out, here is what Wootan and Bonnie Liebman, head of nutrition at CSPI, recommended in a recent issue of their organization's newsletter, Nutrition Action:

* Go easy on the appetizers. CSPI found that such favorites as whole fried onions, cheese fries, mozzarella sticks and Buffalo wings come loaded with both saturated and trans fat.

* Avoid fried food. Choose grilled foods instead, if possible. Forgo mayonnaise and other high-fat toppings, substituting mustard or other low-fat options.

* Start with salads. Most are low in trans fat, unless you chow down a hefty chef's salad loaded with meat and cheese or douse your salad in creamy, high-fat dressing.

AMERICANS' CONSUMPTION OF FAT

Americans on average eat just over five grams of trans fatty acids a day, according to a federal survey of eating habits. These findings were published last year in the Journal of the American Dietetic Association. Public health officials have urged Americans to reduce their fat intake drastically, consuming no more than 30 percent of calories from fat. For a typical diet of 2,000 calories a day, total fat consumption should be about 66 grams, with saturated and trans fat combined limited to 20 grams. The table below shows that most Americans far exceed the recommended level of fat consumption.

Total Saturated Trans Fatty

Fat Fat Acids

Age (grams) (grams) (grams)

Boys and Girls 3-5 54 21 4

Boys and Girls 6-11 69 26 5

Boys 12-19 92 34 7

Girls 12-19 67 25 5

Men 20-49 91 32 7

Women 20-49 61 21 5

Men 50-69 77 26 6

Women 50-69 55 18 4

Men and Women

70 and older 57 19 5

Source: Journal of the American Dietetic Association

HEALTH TALK ONLINE

Got a question about trans fatty acids? Join us today at 2 p.m. for a discussion of this topic on The Washington Post's Internet edition at www.washingtonpost.com/liveonline. Send in your comments and questions.

CAPTION: Nutrition experts say many fast food portions contain extremely high amounts of trans fatty acids.